WEBVTT 00:00:01.680 --> 00:00:04.080 The following content is provided under a Creative 00:00:04.080 --> 00:00:05.620 Commons license. 00:00:05.620 --> 00:00:07.920 Your support will help MIT OpenCourseWare 00:00:07.920 --> 00:00:12.280 continue to offer high quality, educational resources for free. 00:00:12.280 --> 00:00:14.910 To make a donation, or view additional materials 00:00:14.910 --> 00:00:18.870 from hundreds of MIT courses, visit MIT OpenCourseWare 00:00:18.870 --> 00:00:21.360 at ocw.mit.edu. 00:00:21.360 --> 00:00:22.860 JESSICA SOMMERVILLE: So this morning 00:00:22.860 --> 00:00:24.930 we heard Laura give a really beautiful overview 00:00:24.930 --> 00:00:26.747 of her research program, and my talk today 00:00:26.747 --> 00:00:28.330 is going to be a little bit different. 00:00:28.330 --> 00:00:29.700 I'm going to talk about some things that 00:00:29.700 --> 00:00:31.399 are going to be highly related to what 00:00:31.399 --> 00:00:32.940 Laura was talking about, particularly 00:00:32.940 --> 00:00:34.320 at the end of her talk. 00:00:34.320 --> 00:00:37.350 But because this is like brand new hot off the press work, 00:00:37.350 --> 00:00:40.860 some of it's actually ongoing as you'll see as the talk unfolds. 00:00:40.860 --> 00:00:43.650 I'm going to be focusing on a more kind of specific detail 00:00:43.650 --> 00:00:44.150 level. 00:00:44.150 --> 00:00:46.108 So I may tell you about four different studies, 00:00:46.108 --> 00:00:48.779 three of which are completed, one of which is ongoing. 00:00:48.779 --> 00:00:50.820 And they all have to do with infants' sensitivity 00:00:50.820 --> 00:00:53.270 to costs and benefits. 00:00:53.270 --> 00:00:54.190 OK. 00:00:54.190 --> 00:00:56.332 So, as we all know, cost benefit analyses 00:00:56.332 --> 00:00:57.790 are really central to the decisions 00:00:57.790 --> 00:01:00.105 we make at both a conscious and an unconscious level. 00:01:00.105 --> 00:01:02.230 And, of course, there's all kinds of different ways 00:01:02.230 --> 00:01:03.861 that we make decisions, right? 00:01:03.861 --> 00:01:05.319 But one of the things that we often 00:01:05.319 --> 00:01:07.000 do when we're making a decision is 00:01:07.000 --> 00:01:10.660 we think about what rewards do we anticipate from following 00:01:10.660 --> 00:01:12.594 a particular course of action, and how 00:01:12.594 --> 00:01:14.260 do those compare to the costs that we'll 00:01:14.260 --> 00:01:16.900 incur from performing that same action. 00:01:16.900 --> 00:01:18.580 And we will act in a sense to try 00:01:18.580 --> 00:01:22.179 to maximize the value that we get out of a particular choice. 00:01:22.179 --> 00:01:24.220 That's true of simple decisions like this, right? 00:01:24.220 --> 00:01:26.553 This woman deciding what she's going to eat for dessert. 00:01:26.553 --> 00:01:28.180 And we can also apply these analyses 00:01:28.180 --> 00:01:29.950 to more complex decisions, like things 00:01:29.950 --> 00:01:32.449 like where we're going to go to college, what kind of career 00:01:32.449 --> 00:01:34.750 are we going to pursue, where are we going to live. 00:01:34.750 --> 00:01:35.339 OK. 00:01:35.339 --> 00:01:37.630 One of the things that we heard from Laura this morning 00:01:37.630 --> 00:01:39.721 is that cost benefit analyses don't just 00:01:39.721 --> 00:01:41.970 apply to her own behavior and her own decision making. 00:01:41.970 --> 00:01:43.720 She showed some really neat evidence 00:01:43.720 --> 00:01:46.150 that these types of analyses form 00:01:46.150 --> 00:01:48.970 the basis for the inferences that we make about other people 00:01:48.970 --> 00:01:51.010 and that we make about their behavior. 00:01:51.010 --> 00:01:53.140 So that raises the very interesting question 00:01:53.140 --> 00:01:55.605 of the developmental origins of these types analyses. 00:01:55.605 --> 00:01:56.980 And that's what I'm going to talk 00:01:56.980 --> 00:01:58.355 about today, infants' sensitivity 00:01:58.355 --> 00:02:00.872 to costs and benefits. 00:02:00.872 --> 00:02:03.080 My talk is going to kind of have two different parts. 00:02:03.080 --> 00:02:04.496 In the first part, I'm going to be 00:02:04.496 --> 00:02:05.950 talking about cases where infants 00:02:05.950 --> 00:02:07.720 are observing other people. 00:02:07.720 --> 00:02:10.120 And what the question that I'm asking there is 00:02:10.120 --> 00:02:13.210 do infants-- are they able to register the costs that are 00:02:13.210 --> 00:02:15.425 behind other people's actions? 00:02:15.425 --> 00:02:17.050 And then in the second part of my talk, 00:02:17.050 --> 00:02:18.250 I'm actually going to switch gears, 00:02:18.250 --> 00:02:20.440 and I'm going to talk about infants' registration 00:02:20.440 --> 00:02:23.579 and minimization of costs, the registration of benefits, 00:02:23.579 --> 00:02:25.870 to guide their own behavior, their own decision making. 00:02:25.870 --> 00:02:27.872 I'm going to talk about a particular test case. 00:02:27.872 --> 00:02:30.205 And that's the test case of infants' prosocial behavior. 00:02:33.310 --> 00:02:34.180 OK. 00:02:34.180 --> 00:02:35.860 And I want to be kind of specific here. 00:02:35.860 --> 00:02:37.450 So across all of these studies, I'm 00:02:37.450 --> 00:02:39.250 talking about cost in one particular way. 00:02:39.250 --> 00:02:40.750 Of course, there's all kinds of ways 00:02:40.750 --> 00:02:42.640 you could operationalize cost. 00:02:42.640 --> 00:02:44.470 But what we've been focusing on so far 00:02:44.470 --> 00:02:46.540 is physical effort, the physical effort 00:02:46.540 --> 00:02:48.880 behind an action as a cost. 00:02:48.880 --> 00:02:50.662 Why would we start here? 00:02:50.662 --> 00:02:52.620 Well, there's several different reasons, right? 00:02:52.620 --> 00:02:55.090 And the basic kind of evolutionary level, it's 00:02:55.090 --> 00:02:57.910 really important that we can register 00:02:57.910 --> 00:03:00.070 and that we can minimize energetic costs, 00:03:00.070 --> 00:03:01.150 effortful costs, right? 00:03:01.150 --> 00:03:02.830 Our very survival depends on that. 00:03:02.830 --> 00:03:05.050 We have to metabolically and energetically budget, 00:03:05.050 --> 00:03:07.044 or we won't stick around, right? 00:03:07.044 --> 00:03:08.710 So that gives us good reason that that's 00:03:08.710 --> 00:03:11.860 a good starting place in terms of looking at young infants' 00:03:11.860 --> 00:03:16.390 ability to register costs and minimize cost potentially. 00:03:16.390 --> 00:03:19.240 Another reason is that for decades, scholars 00:03:19.240 --> 00:03:22.970 have really given a central role to effort in decision-making. 00:03:22.970 --> 00:03:24.490 And this dates back to the 1940s, 00:03:24.490 --> 00:03:26.170 the whole in Solomon who postulated 00:03:26.170 --> 00:03:27.580 the law of least effort. 00:03:27.580 --> 00:03:30.406 So the idea here is that if there are two lines of actions 00:03:30.406 --> 00:03:31.780 that lead to equal rewards, we're 00:03:31.780 --> 00:03:33.863 going to take the path of least resistance, right? 00:03:33.863 --> 00:03:36.250 We're going to seek to minimize effort. 00:03:36.250 --> 00:03:38.530 And then, finally, in more contemporary work 00:03:38.530 --> 00:03:40.570 that's looked at cost-benefit decision-making, 00:03:40.570 --> 00:03:43.120 both in adults and in nonhuman animals, a lot of this work 00:03:43.120 --> 00:03:46.530 comes from the neuroimaging literature. 00:03:46.530 --> 00:03:49.125 Effort has been a fairly heavily studied cost. 00:03:49.125 --> 00:03:50.500 So this is a good starting place, 00:03:50.500 --> 00:03:52.583 because we have a pretty good understanding of how 00:03:52.583 --> 00:03:55.030 effort and various benefits or reward are integrated 00:03:55.030 --> 00:03:57.010 at both the neural and a behavioral level, 00:03:57.010 --> 00:04:01.930 at least for nonhuman animals and for human adults. 00:04:01.930 --> 00:04:02.740 OK. 00:04:02.740 --> 00:04:04.690 So the first question we might ask 00:04:04.690 --> 00:04:06.820 is, what is the existing evidence 00:04:06.820 --> 00:04:08.710 in terms of the question of whether infants 00:04:08.710 --> 00:04:11.909 have a basic ability to register cost behind actions. 00:04:11.909 --> 00:04:13.450 And there's really two different ways 00:04:13.450 --> 00:04:14.620 we could pose this question. 00:04:14.620 --> 00:04:16.899 We can think about the question with respect 00:04:16.899 --> 00:04:19.390 to infants own behavior, their own actions. 00:04:19.390 --> 00:04:23.260 Is there evidence that infants will act to recognize costs 00:04:23.260 --> 00:04:25.890 and to minimize costs in their own behavior. 00:04:25.890 --> 00:04:27.640 The other way that we can ask the question 00:04:27.640 --> 00:04:29.980 is in terms of infants observation of other people's 00:04:29.980 --> 00:04:30.480 behavior. 00:04:30.480 --> 00:04:34.972 Do they recognize the cost behind other people's actions. 00:04:34.972 --> 00:04:36.430 You know, surprisingly there really 00:04:36.430 --> 00:04:38.290 hasn't been a lot of work that's looked directly 00:04:38.290 --> 00:04:40.000 at this when we're talking about infants 00:04:40.000 --> 00:04:42.620 own behavior, their own decision making. 00:04:42.620 --> 00:04:44.970 There is some work from the weight perception literature 00:04:44.970 --> 00:04:46.660 that's looked at how infants interact 00:04:46.660 --> 00:04:48.049 with blocks of different ways. 00:04:48.049 --> 00:04:49.840 And so what people will do in these studies 00:04:49.840 --> 00:04:52.215 is they'll present little babies, nine-month-old infants, 00:04:52.215 --> 00:04:55.030 with two blocks that look virtually identical. 00:04:55.030 --> 00:04:56.560 They only differ from one another 00:04:56.560 --> 00:04:58.665 in terms of their respective weights. 00:04:58.665 --> 00:05:00.040 And what these studies have shown 00:05:00.040 --> 00:05:02.260 is if you give infants a choice between these two objects, 00:05:02.260 --> 00:05:04.330 they'll systematically prefer the light object 00:05:04.330 --> 00:05:05.897 over the heavy object. 00:05:05.897 --> 00:05:08.230 So one way to think about these findings is what infants 00:05:08.230 --> 00:05:10.840 are doing here is exactly what we're interested 00:05:10.840 --> 00:05:12.850 in, they're minimizing the physical cost, right? 00:05:12.850 --> 00:05:15.756 They're taking the past of-- the path of least effort. 00:05:15.756 --> 00:05:17.380 One challenge, though, for interpreting 00:05:17.380 --> 00:05:19.630 these finding is oftentimes in these studies, 00:05:19.630 --> 00:05:21.130 the heavy blocks that are being used 00:05:21.130 --> 00:05:23.370 are beyond infants lifting capacity. 00:05:23.370 --> 00:05:25.870 So what that means is it's hard to know if these results are 00:05:25.870 --> 00:05:27.874 about infants registering cost per se, 00:05:27.874 --> 00:05:29.290 or if what we're really getting at 00:05:29.290 --> 00:05:32.500 is just infants repeating a sort of successful interaction 00:05:32.500 --> 00:05:35.960 with an object that they've acted on previously. 00:05:35.960 --> 00:05:36.460 OK. 00:05:36.460 --> 00:05:38.680 So Laura talked a little bit about this in her talk today. 00:05:38.680 --> 00:05:40.680 What about the evidence of registration of costs 00:05:40.680 --> 00:05:41.971 and other people's actions. 00:05:41.971 --> 00:05:43.720 And one of the things that Laura mentioned 00:05:43.720 --> 00:05:46.030 that we know from many, many different studies, 00:05:46.030 --> 00:05:48.370 is that infants appear to expect efficiency 00:05:48.370 --> 00:05:49.870 in other people's actions. 00:05:49.870 --> 00:05:51.490 Laura showed you one example of that. 00:05:51.490 --> 00:05:52.760 I'll show you a different example 00:05:52.760 --> 00:05:54.510 of that, which comes from actually a study 00:05:54.510 --> 00:05:56.709 that Liz did with one of her graduate students. 00:05:56.709 --> 00:05:58.250 So here we see someone who's reaching 00:05:58.250 --> 00:06:00.080 over a barrier in order to get an object. 00:06:00.080 --> 00:06:01.670 The barrier is then removed. 00:06:01.670 --> 00:06:03.870 Infants have the expectation that that person 00:06:03.870 --> 00:06:05.620 is going to reach directly for the object, 00:06:05.620 --> 00:06:08.640 right, rather than performing that funny arcing motion. 00:06:08.640 --> 00:06:10.730 So, again, one way to think about these findings 00:06:10.730 --> 00:06:12.260 is that what infants are doing is 00:06:12.260 --> 00:06:14.060 they're expecting that the person is going to take 00:06:14.060 --> 00:06:15.380 the least costly action, right? 00:06:15.380 --> 00:06:17.510 And, in fact, there's all kinds of costs 00:06:17.510 --> 00:06:19.430 to this particular arcing motion, right? 00:06:19.430 --> 00:06:21.950 It's indirect, it probably takes longer, 00:06:21.950 --> 00:06:26.396 it's probably more difficult, it's more effortful. 00:06:26.396 --> 00:06:28.145 And so we wanted to ask the question, too, 00:06:28.145 --> 00:06:31.550 to begin with if infants were able to register costs. 00:06:31.550 --> 00:06:33.320 But unlike in this situation where 00:06:33.320 --> 00:06:35.740 there's multiple potentially redundant cues 00:06:35.740 --> 00:06:38.630 that this arching motion is a costly behavior, 00:06:38.630 --> 00:06:40.310 we wanted to really kind of focus 00:06:40.310 --> 00:06:42.830 in on situations in which there aren't 00:06:42.830 --> 00:06:45.980 a lot of overt observable cues to the costs underlying 00:06:45.980 --> 00:06:46.980 another person's action. 00:06:50.100 --> 00:06:52.680 So the way that we did this is we showed infants 00:06:52.680 --> 00:06:56.820 different actions that look similar on their surface level, 00:06:56.820 --> 00:06:58.299 but these actions differ in terms 00:06:58.299 --> 00:07:00.840 of the degree of physical effort that are required to perform 00:07:00.840 --> 00:07:02.490 them, and the way that we achieve 00:07:02.490 --> 00:07:05.464 that is by having infants watch people lift objects 00:07:05.464 --> 00:07:06.630 of different weights, right? 00:07:06.630 --> 00:07:10.180 So, obviously, heavy weighted objects are harder to lift. 00:07:10.180 --> 00:07:14.830 They're more effortly costly than lifting a light object. 00:07:14.830 --> 00:07:17.070 And what we wanted to know is can infants 00:07:17.070 --> 00:07:20.400 recognize under conditions where they have really minimal, 00:07:20.400 --> 00:07:23.280 observable cues, no cues about, for example, straining 00:07:23.280 --> 00:07:24.810 or sweating or things like that that 00:07:24.810 --> 00:07:27.480 might be really obvious for figuring out the effort. 00:07:27.480 --> 00:07:30.109 Will they be able to understand that when someone is lifting 00:07:30.109 --> 00:07:32.400 a heavy block, that's a more effortful action than when 00:07:32.400 --> 00:07:35.460 they're lifting a light block. 00:07:35.460 --> 00:07:37.390 In addition to that kind of primary question, 00:07:37.390 --> 00:07:39.990 we were also interested in whether this ability in infants 00:07:39.990 --> 00:07:42.074 might be individually variable. 00:07:42.074 --> 00:07:43.740 So this might come as a surprise to you, 00:07:43.740 --> 00:07:46.755 but infants, like adults, are individually variable. 00:07:46.755 --> 00:07:48.630 And they're individually variable, of course, 00:07:48.630 --> 00:07:49.380 in many ways. 00:07:49.380 --> 00:07:51.450 But one way in which they vary from one another 00:07:51.450 --> 00:07:53.199 is in terms of how strong they are, right? 00:07:53.199 --> 00:07:54.880 Just like human adults, right? 00:07:54.880 --> 00:07:57.900 We're variable in terms of how strong we are. 00:07:57.900 --> 00:08:00.240 And we have an idea, or hypothesis, 00:08:00.240 --> 00:08:02.820 that infants individual differences in strength 00:08:02.820 --> 00:08:05.029 might actually be important for registering 00:08:05.029 --> 00:08:07.320 the effort-related costs behind these different lifting 00:08:07.320 --> 00:08:09.502 actions with different weighted objects. 00:08:09.502 --> 00:08:11.460 One of the reasons that they might be important 00:08:11.460 --> 00:08:14.580 is because of core strength gates the type of experience 00:08:14.580 --> 00:08:17.250 that infants are going to have in their everyday life, right? 00:08:17.250 --> 00:08:19.860 If you're a strong baby, you can lift heavier objects 00:08:19.860 --> 00:08:20.820 than a weak baby. 00:08:20.820 --> 00:08:24.030 You can also lift a wider contrast of range of objects, 00:08:24.030 --> 00:08:24.750 right? 00:08:24.750 --> 00:08:26.370 So we thought maybe there's something 00:08:26.370 --> 00:08:29.100 about individual differences in strength, particularly, 00:08:29.100 --> 00:08:30.930 for babies who are stronger where they'll 00:08:30.930 --> 00:08:33.960 be better at recognizing the differential effort that 00:08:33.960 --> 00:08:35.610 goes along with lifting actions when 00:08:35.610 --> 00:08:38.980 you're talking about blocks of different weight. 00:08:38.980 --> 00:08:39.480 OK. 00:08:39.480 --> 00:08:41.010 So let me tell you about the study 00:08:41.010 --> 00:08:43.559 that we conducted to ask this question. 00:08:43.559 --> 00:08:45.570 We tested 12-month-old infants in this study. 00:08:45.570 --> 00:08:47.880 They took part in a turn taking procedure 00:08:47.880 --> 00:08:49.920 where we recorded EEG, electrical activity 00:08:49.920 --> 00:08:52.580 from the brain as it propagates the scalp. 00:08:52.580 --> 00:08:55.050 And in the course of this task, what they did is 00:08:55.050 --> 00:08:57.470 they took part in different types of trials. 00:08:57.470 --> 00:09:00.720 On observation trials, they would watch an experimenter who 00:09:00.720 --> 00:09:03.720 would lift these different objects or these blocks, 00:09:03.720 --> 00:09:06.030 and these blocks looked perceptually identical 00:09:06.030 --> 00:09:07.240 in terms of size and shape. 00:09:07.240 --> 00:09:09.300 They were different colors so infants could individuate them 00:09:09.300 --> 00:09:12.090 and keep track of them, but what varied from trial to trial 00:09:12.090 --> 00:09:13.980 was exactly how much the objects weighed. 00:09:13.980 --> 00:09:17.700 So they range from being the weight of a typical bath toy 00:09:17.700 --> 00:09:19.500 to being quite heavy. 00:09:19.500 --> 00:09:21.689 So infants can lift the heaviest blocks, 00:09:21.689 --> 00:09:23.730 but they're pretty effortful in order for infants 00:09:23.730 --> 00:09:25.200 to be able to lift them. 00:09:25.200 --> 00:09:27.810 In the trials where they watched an experiment or interact 00:09:27.810 --> 00:09:29.268 with these blocks, the experimenter 00:09:29.268 --> 00:09:31.740 would do things like put the block up on a platform, 00:09:31.740 --> 00:09:35.370 drop it into a bucket after full type of actions where you can 00:09:35.370 --> 00:09:37.920 sort of register at least in principle 00:09:37.920 --> 00:09:39.930 the type of effort behind the action, 00:09:39.930 --> 00:09:42.430 and then infants would also have the opportunity to act. 00:09:42.430 --> 00:09:45.340 They could perform the same actions with objects. 00:09:45.340 --> 00:09:47.250 Infants also for measurement purpose 00:09:47.250 --> 00:09:49.470 received baseline trials where we're just 00:09:49.470 --> 00:09:52.620 registering EEG in response to abstract images 00:09:52.620 --> 00:09:54.970 like a checkerboard pattern, for example. 00:09:54.970 --> 00:09:55.470 OK. 00:09:55.470 --> 00:09:57.880 So what are we interested in here? 00:09:57.880 --> 00:09:59.490 So, in this particular study, we were 00:09:59.490 --> 00:10:01.740 looking at the suppression of a particular oscillatory 00:10:01.740 --> 00:10:04.110 frequency called sensorimotor alpha, 00:10:04.110 --> 00:10:07.930 or some people call it mu attenuation. 00:10:07.930 --> 00:10:10.050 So we know that at rest, neurons in sensorimotor 00:10:10.050 --> 00:10:14.440 cortex fire spontaneously and they fire in synchrony. 00:10:14.440 --> 00:10:16.980 And what that means is we get these large amplitude EEG 00:10:16.980 --> 00:10:20.670 oscillations in the alpha frequency band. 00:10:20.670 --> 00:10:23.190 When the motor cortex is activated in remote motor 00:10:23.190 --> 00:10:25.390 cortex is activated, and that happens, of course, 00:10:25.390 --> 00:10:25.980 when we act. 00:10:25.980 --> 00:10:29.040 It also happens when we watch other people act. 00:10:29.040 --> 00:10:31.620 What you see is you see a suppression in sensorimotor 00:10:31.620 --> 00:10:33.720 alpha. 00:10:33.720 --> 00:10:35.730 So many people recently have been interested 00:10:35.730 --> 00:10:38.250 in suppression of sensorimotor alpha new attenuation 00:10:38.250 --> 00:10:41.130 from the perspective of looking at the mirror neuron system. 00:10:41.130 --> 00:10:42.910 More broadly and for our purposes, 00:10:42.910 --> 00:10:44.670 we're really just thinking about this 00:10:44.670 --> 00:10:47.520 as a measure of sensorimotor cortex activation. 00:10:47.520 --> 00:10:50.580 So greater suppression equals more sensorimotor cortex 00:10:50.580 --> 00:10:52.920 activation. 00:10:52.920 --> 00:10:56.250 And our question here was whether infants activation 00:10:56.250 --> 00:10:58.200 sensorimotor cortex wouldn't vary 00:10:58.200 --> 00:11:00.390 as a function of watching people lift 00:11:00.390 --> 00:11:01.560 blocks of different weights. 00:11:01.560 --> 00:11:04.140 Would you get greater activation when people 00:11:04.140 --> 00:11:06.270 were lifting heavier objects? 00:11:06.270 --> 00:11:07.694 Which would, of course, be a sign 00:11:07.694 --> 00:11:10.110 that infants were distinguishing between different actions 00:11:10.110 --> 00:11:12.651 on the basis of effort. 00:11:12.651 --> 00:11:13.150 OK. 00:11:13.150 --> 00:11:15.820 So in addition to looking at that, 00:11:15.820 --> 00:11:18.040 we also gave infants a group strength assessment. 00:11:18.040 --> 00:11:18.540 OK. 00:11:18.540 --> 00:11:20.220 So let me tell you a little bit about the grip strength 00:11:20.220 --> 00:11:22.594 measure, only because it took us several years to come up 00:11:22.594 --> 00:11:25.800 with this so I feel like I need to talk about it a little bit. 00:11:25.800 --> 00:11:28.230 So we wanted to measure infant strength, and the way 00:11:28.230 --> 00:11:30.150 that we did that is by measuring infants' grip strength. 00:11:30.150 --> 00:11:31.410 But, of course, the challenge here, 00:11:31.410 --> 00:11:32.610 if you're an adult, right, and you 00:11:32.610 --> 00:11:34.200 want to measure an adult's grip strength, 00:11:34.200 --> 00:11:36.120 you just get something called the dynamometer, 00:11:36.120 --> 00:11:38.400 you have an adult squeeze a bulb or squeeze the hand grip 00:11:38.400 --> 00:11:40.560 and then you get this nice force reading from that, right? 00:11:40.560 --> 00:11:43.040 And that all works very smoothly with adults but, of course, you 00:11:43.040 --> 00:11:44.040 can't just hand that to an infant 00:11:44.040 --> 00:11:45.539 and say, squeeze as hard as you can, 00:11:45.539 --> 00:11:47.220 that doesn't work, obviously. 00:11:47.220 --> 00:11:49.930 So what we did here is we had an experimenter who had a toy, 00:11:49.930 --> 00:11:51.580 the infant had the same toy. 00:11:51.580 --> 00:11:54.340 The experimenter would squeeze her toy, and what we hoped 00:11:54.340 --> 00:11:56.710 is that this would motivate infants, or lead infants, 00:11:56.710 --> 00:11:58.420 to squeeze their toy. 00:11:58.420 --> 00:12:01.540 Their toy, in contrast to the experimenter's toy, 00:12:01.540 --> 00:12:05.830 had both a hidden sensor embedded within the toy, which 00:12:05.830 --> 00:12:08.080 led to playing Old McDonald, which, of course, 00:12:08.080 --> 00:12:09.530 infants greatly like, right? 00:12:09.530 --> 00:12:11.200 They find that very enjoyable. 00:12:11.200 --> 00:12:14.420 And it also had a hidden pressure sensor within it. 00:12:14.420 --> 00:12:16.720 So we were able to get-- or to measure how 00:12:16.720 --> 00:12:18.584 hard infants squeezed the toy. 00:12:18.584 --> 00:12:20.500 Now, the trick here was we want to get infants 00:12:20.500 --> 00:12:21.541 strongest squeeze, right? 00:12:21.541 --> 00:12:23.440 So what we did is we set up our device so 00:12:23.440 --> 00:12:25.690 that each time the infant squeezes it, 00:12:25.690 --> 00:12:28.300 they have to squeeze harder to get Old McDonald to play. 00:12:28.300 --> 00:12:30.670 And, of course, they want Old McDonald to play, right? 00:12:30.670 --> 00:12:32.630 So they're motivated to keep doing that. 00:12:32.630 --> 00:12:34.930 So that's how we record infants' maximum grip strength. 00:12:34.930 --> 00:12:37.420 We like essentially keep going as long as infants will 00:12:37.420 --> 00:12:39.656 allow us to do that, basically. 00:12:39.656 --> 00:12:41.530 There are some other things that we measured. 00:12:41.530 --> 00:12:43.030 We measured infants weight. 00:12:43.030 --> 00:12:45.946 Our motivation for doing this is that an adults' strength 00:12:45.946 --> 00:12:47.320 and weight are highly correlated. 00:12:47.320 --> 00:12:49.695 They were in our sample so that kind of helps to validate 00:12:49.695 --> 00:12:51.130 or grip strength paradigm. 00:12:51.130 --> 00:12:53.860 And there were things like general motor maturity that we 00:12:53.860 --> 00:12:56.170 measured, gross motor skills. 00:12:56.170 --> 00:12:58.324 We measured how frequently infants lift blocks 00:12:58.324 --> 00:13:00.490 within the task, because we want a control for these 00:13:00.490 --> 00:13:01.210 in our analyses. 00:13:01.210 --> 00:13:02.626 We're wanting to look specifically 00:13:02.626 --> 00:13:04.910 at the effective grip strength. 00:13:04.910 --> 00:13:06.140 OK. 00:13:06.140 --> 00:13:06.640 OK. 00:13:06.640 --> 00:13:10.127 So let me tell you a bit-- the first thing that we looked at. 00:13:10.127 --> 00:13:12.210 So I'm going to show you a series of scatter plots 00:13:12.210 --> 00:13:14.830 that look at the relation between sensorimotor alpha 00:13:14.830 --> 00:13:17.620 suppression, and infant's grip strength. 00:13:17.620 --> 00:13:19.750 And these are plotted as a function 00:13:19.750 --> 00:13:21.460 of the weight of the block. 00:13:21.460 --> 00:13:24.847 And these are when infants are observing other people. 00:13:24.847 --> 00:13:27.180 So the thing to know is we're talking about suppression, 00:13:27.180 --> 00:13:28.763 so you're looking for negative scores. 00:13:28.763 --> 00:13:31.450 More negative scores mean more suppression. 00:13:31.450 --> 00:13:33.130 And we had a particular hypothesis 00:13:33.130 --> 00:13:35.920 about how this would go, or idea about how this would go. 00:13:35.920 --> 00:13:39.070 We thought that when the blocks were relatively light, 00:13:39.070 --> 00:13:41.630 grip strength would be less of a good predictor 00:13:41.630 --> 00:13:43.600 of sensorimotor alpha suppression. 00:13:43.600 --> 00:13:45.310 And the reason for thinking that is 00:13:45.310 --> 00:13:48.100 that whether an infant is relatively strong or relatively 00:13:48.100 --> 00:13:50.770 weak, they all probably have lifetime experience lifting 00:13:50.770 --> 00:13:52.700 relatively light objects. 00:13:52.700 --> 00:13:54.800 However, where strength really comes into play 00:13:54.800 --> 00:13:57.160 is as objects get heavier, right? 00:13:57.160 --> 00:13:59.410 So stronger infants, very likely, 00:13:59.410 --> 00:14:03.640 have a greater lifetime history of lifting heavier objects. 00:14:03.640 --> 00:14:05.470 So our prediction was that these two things 00:14:05.470 --> 00:14:09.100 would be increasingly tightly integrated as block weight goes 00:14:09.100 --> 00:14:10.130 up. 00:14:10.130 --> 00:14:12.460 And, in fact, that's exactly what we found. 00:14:12.460 --> 00:14:15.340 So there's weak relations when the block is light, 00:14:15.340 --> 00:14:17.110 when it's that heavy block-- 00:14:17.110 --> 00:14:19.420 we call them the heavy and the super heavy block-- 00:14:19.420 --> 00:14:20.590 there's a tighter relation. 00:14:20.590 --> 00:14:22.750 And you see the strongest relation here 00:14:22.750 --> 00:14:25.510 when the block is extremely heavy. 00:14:25.510 --> 00:14:28.030 And these analyses control for things 00:14:28.030 --> 00:14:30.610 like infants in task lifting experience, their weight, 00:14:30.610 --> 00:14:32.842 their motor development scores. 00:14:32.842 --> 00:14:34.300 So the next thing we wanted to know 00:14:34.300 --> 00:14:35.716 is we wanted to know whether there 00:14:35.716 --> 00:14:38.110 was any evidence that suppression of sensorimotor 00:14:38.110 --> 00:14:43.060 alpha would be greater in cases in which the block is heaviest 00:14:43.060 --> 00:14:44.710 versus the block is lightest. 00:14:44.710 --> 00:14:46.965 So this is really our index, or our measure, 00:14:46.965 --> 00:14:49.090 of whether infants are differentiating when they're 00:14:49.090 --> 00:14:52.000 watching other people act on objects, whether they're 00:14:52.000 --> 00:14:55.150 differentiating the degree of effort that goes along 00:14:55.150 --> 00:14:57.580 with lifting the object as a function of block weight. 00:14:57.580 --> 00:14:59.538 So what I'm going to show you is change scores. 00:14:59.538 --> 00:15:01.300 So more negative means that you're 00:15:01.300 --> 00:15:05.200 seeing increasing sensorimotor alpha suppression for heavy 00:15:05.200 --> 00:15:06.700 versus light blocks, and these are 00:15:06.700 --> 00:15:09.449 plotted as a function of infants' grip strength. 00:15:09.449 --> 00:15:11.740 So what you can see here is that for the weaker babies, 00:15:11.740 --> 00:15:13.781 the lower grip strength babies, you're not really 00:15:13.781 --> 00:15:16.060 seeing any systematic change from the latest 00:15:16.060 --> 00:15:17.475 block to the heaviest block. 00:15:17.475 --> 00:15:19.840 But you are for the stronger infants. 00:15:19.840 --> 00:15:22.510 So what these findings suggest to us is that the stronger 00:15:22.510 --> 00:15:24.912 infants appear to be differentiating these actions 00:15:24.912 --> 00:15:27.370 on the basis of the weight of the object that the person is 00:15:27.370 --> 00:15:30.950 lifting, the weaker infants aren't. 00:15:30.950 --> 00:15:31.450 OK. 00:15:31.450 --> 00:15:33.489 So what do we know from this data. 00:15:33.489 --> 00:15:35.280 Well, we have some evidence that activation 00:15:35.280 --> 00:15:37.750 of sensorimotor cortex as indexed by suppression 00:15:37.750 --> 00:15:40.330 of sensorimotor alpha, while babies are watching 00:15:40.330 --> 00:15:42.306 other people lift blocks of different weights, 00:15:42.306 --> 00:15:44.680 varies as the function of the weight of the block, right? 00:15:44.680 --> 00:15:46.360 So this might signal that infants 00:15:46.360 --> 00:15:49.330 are able to recognize that different actions have 00:15:49.330 --> 00:15:53.860 different degrees of physical effort that go along with them. 00:15:53.860 --> 00:15:56.440 And we also see that the ability to make this distinction 00:15:56.440 --> 00:15:59.800 is tied to infants own strength, their own grip strength. 00:15:59.800 --> 00:16:01.450 And our interpretation of this is 00:16:01.450 --> 00:16:04.420 that this might have to do with strength being 00:16:04.420 --> 00:16:06.310 a rate limiter, or a facilitator, 00:16:06.310 --> 00:16:08.890 or the type of experience that infants previously 00:16:08.890 --> 00:16:11.454 have with objects of different weights. 00:16:11.454 --> 00:16:13.120 And, in particular, the stronger infants 00:16:13.120 --> 00:16:15.580 might have more experience with lifting heavier objects. 00:16:15.580 --> 00:16:18.040 They might have more contrastive experience, which 00:16:18.040 --> 00:16:20.494 allows them to better recognize, or better differentiate, 00:16:20.494 --> 00:16:21.910 the degree of physical effort that 00:16:21.910 --> 00:16:23.680 go along with different actions when 00:16:23.680 --> 00:16:27.540 you're talking about lifting objects of different weight. 00:16:27.540 --> 00:16:28.450 OK. 00:16:28.450 --> 00:16:30.130 So that's part one. 00:16:30.130 --> 00:16:32.980 So I think what these data tell us is that in this context, 00:16:32.980 --> 00:16:34.660 infants have a means of registering 00:16:34.660 --> 00:16:35.680 effort related costs. 00:16:35.680 --> 00:16:38.290 I think where they go above past data is that they tell us 00:16:38.290 --> 00:16:41.410 that infants can do this under conditions in which they 00:16:41.410 --> 00:16:42.720 have minimal behavioral cues. 00:16:42.720 --> 00:16:44.720 So we think back to that reaching action, right? 00:16:44.720 --> 00:16:48.550 There's all kinds of cues that this is a costly action, right? 00:16:48.550 --> 00:16:51.230 There's all kinds of ways that it differs from a direct reach. 00:16:51.230 --> 00:16:54.020 In this situation, we're talking about actions 00:16:54.020 --> 00:16:57.230 that are really minimally different from one another. 00:16:57.230 --> 00:16:59.570 What I want to do now is I want to switch gears and talk 00:16:59.570 --> 00:17:01.850 about kind of the flip side of the coin. 00:17:01.850 --> 00:17:04.099 And that is infants use of costs and benefits, 00:17:04.099 --> 00:17:05.780 or reward, to guide their own behavior. 00:17:05.780 --> 00:17:07.550 And I'm going to be specifically focusing 00:17:07.550 --> 00:17:11.919 on the test case of infants prosocial behavior. 00:17:11.919 --> 00:17:13.460 So many of you may know this already, 00:17:13.460 --> 00:17:15.560 but infants are highly prosocial, right? 00:17:15.560 --> 00:17:17.528 There's been a lot of studies on this recently, 00:17:17.528 --> 00:17:19.069 and all of these studies have kind of 00:17:19.069 --> 00:17:20.780 come down on the conclusion that starting 00:17:20.780 --> 00:17:22.238 in the second year of life, infants 00:17:22.238 --> 00:17:24.920 will do things like help people achieve their goals, 00:17:24.920 --> 00:17:27.099 they will share toys or objects with other people, 00:17:27.099 --> 00:17:29.960 they're comfort people in distress. 00:17:29.960 --> 00:17:31.820 But there are questions and debates 00:17:31.820 --> 00:17:34.370 that are hotly contested about early prosocial development, 00:17:34.370 --> 00:17:38.760 and I just want to bring two of them to your attention. 00:17:38.760 --> 00:17:39.650 OK. 00:17:39.650 --> 00:17:42.560 So one question is, when does infants or children's 00:17:42.560 --> 00:17:46.880 prosocial behavior become selective or strategic, right? 00:17:46.880 --> 00:17:48.710 So we know that by preschool age, 00:17:48.710 --> 00:17:51.110 early school age, children's prosocial behavior 00:17:51.110 --> 00:17:52.841 is somewhat selective, meaning that there 00:17:52.841 --> 00:17:54.590 are some people, for example, that infants 00:17:54.590 --> 00:17:57.190 are more likely to help than others, right? 00:17:57.190 --> 00:17:59.990 And children are-- not infants, children-- children 00:17:59.990 --> 00:18:02.570 are more likely to help under situations 00:18:02.570 --> 00:18:06.080 where they are perhaps reputational concerns involved. 00:18:06.080 --> 00:18:08.510 But what we don't yet know is whether this 00:18:08.510 --> 00:18:10.922 is true of very early prosocial development. 00:18:10.922 --> 00:18:12.630 So what is the developmental course like? 00:18:12.630 --> 00:18:15.710 Do kids start off being selective and strategic? 00:18:15.710 --> 00:18:18.080 Or do they only get there over time with development? 00:18:18.080 --> 00:18:19.539 That's one question. 00:18:19.539 --> 00:18:21.080 There's another related question that 00:18:21.080 --> 00:18:23.420 has to do with what is the underlying motivation 00:18:23.420 --> 00:18:26.000 for prosocial behavior, right? 00:18:26.000 --> 00:18:27.890 So the kind of generous interpretation 00:18:27.890 --> 00:18:31.640 of infants prosocial is actions, children's prosocial action, 00:18:31.640 --> 00:18:34.086 is what is going on here is infants are motivated 00:18:34.086 --> 00:18:35.210 by empathic concern, right? 00:18:35.210 --> 00:18:36.751 They care about other people's needs, 00:18:36.751 --> 00:18:38.690 they care about other people's desires. 00:18:38.690 --> 00:18:40.250 And in these experimental context, 00:18:40.250 --> 00:18:42.830 what they're doing is they're acting to meet another person's 00:18:42.830 --> 00:18:45.260 needs, they're acting out of empathic concern. 00:18:45.260 --> 00:18:47.780 But there's also other reasons why infants, or anyone, 00:18:47.780 --> 00:18:49.750 for that matter, might behave prosocially, 00:18:49.750 --> 00:18:52.520 that might have to do with social affiliation 00:18:52.520 --> 00:18:55.880 biases, social motivation, that might have 00:18:55.880 --> 00:18:58.400 to do with wanting to see a goal being completed, 00:18:58.400 --> 00:19:01.490 et cetera, right? 00:19:01.490 --> 00:19:03.680 So one of the ways that we can start to get traction 00:19:03.680 --> 00:19:07.070 on these issues is by looking at the impact of various costs 00:19:07.070 --> 00:19:08.390 on infants' prosocial behavior. 00:19:08.390 --> 00:19:11.060 And somewhat surprisingly, this is not a terribly well studied 00:19:11.060 --> 00:19:12.870 topic as of yet. 00:19:12.870 --> 00:19:15.089 So there are some studies that are both with infants 00:19:15.089 --> 00:19:16.880 and with children, where people have looked 00:19:16.880 --> 00:19:20.250 at the impact of personal cost on prosocial behavior 00:19:20.250 --> 00:19:22.670 and, usually, the way personal costs are operationalized 00:19:22.670 --> 00:19:24.599 is in terms of, let's say, an infant 00:19:24.599 --> 00:19:27.140 is tested in a paradigm where they need to help someone else, 00:19:27.140 --> 00:19:28.869 or share an object with someone else. 00:19:28.869 --> 00:19:30.410 And they might be required to give up 00:19:30.410 --> 00:19:33.000 their own object versus an object that's just sitting 00:19:33.000 --> 00:19:34.000 there in the lab, right? 00:19:34.000 --> 00:19:37.900 Presumably, their own object has higher personal cost. 00:19:37.900 --> 00:19:41.300 Now, we don't really know when personal costs start 00:19:41.300 --> 00:19:42.920 to impact infants' prosocial behavior, 00:19:42.920 --> 00:19:44.900 because there's been a lot of mixed evidence. 00:19:44.900 --> 00:19:47.270 And, particularly, in infancy, there's, as of yet, 00:19:47.270 --> 00:19:50.490 no systematic evidence that high personal costs actually reduce 00:19:50.490 --> 00:19:53.174 infants' prosocial responding. 00:19:53.174 --> 00:19:55.340 What about the question of energetic physical effort 00:19:55.340 --> 00:19:56.510 related costs? 00:19:56.510 --> 00:19:58.890 Well, again, here, this is really an understudy topic. 00:19:58.890 --> 00:20:00.350 So there's one existing study that 00:20:00.350 --> 00:20:02.030 has looked at infants helping under kind 00:20:02.030 --> 00:20:05.279 of minimal physical effort cost. 00:20:05.279 --> 00:20:07.820 And it's a little bit hard to know what to make of that study 00:20:07.820 --> 00:20:09.740 because we know that infants helping behavior 00:20:09.740 --> 00:20:11.679 is still present under those conditions, 00:20:11.679 --> 00:20:13.970 we just don't really know how it compares to conditions 00:20:13.970 --> 00:20:15.770 where the physical costs are low. 00:20:18.060 --> 00:20:18.560 OK. 00:20:18.560 --> 00:20:21.410 So we started off by asking a really super simple question 00:20:21.410 --> 00:20:23.180 about infants prosocial behavior, 00:20:23.180 --> 00:20:26.480 and that was whether the anticipated physical effort 00:20:26.480 --> 00:20:28.850 that goes along with prosocial responding 00:20:28.850 --> 00:20:31.160 influences infants prosocial responding. 00:20:31.160 --> 00:20:33.710 In particular, when the effort is high, does it increase, 00:20:33.710 --> 00:20:36.070 or rather, decrease infants prosociality. 00:20:38.710 --> 00:20:39.210 OK. 00:20:39.210 --> 00:20:42.396 So we tested 18-month-old infants in this study. 00:20:42.396 --> 00:20:44.520 Start by telling you about the critical test phase, 00:20:44.520 --> 00:20:45.900 it was a helping task. 00:20:45.900 --> 00:20:48.307 An experimenter was on the opposite side of the room. 00:20:48.307 --> 00:20:49.890 She needs a block in order to complete 00:20:49.890 --> 00:20:52.140 a tower that she's building. 00:20:52.140 --> 00:20:53.981 What happens before that is all infants 00:20:53.981 --> 00:20:55.230 take part in a training phase. 00:20:55.230 --> 00:20:56.813 They're faced with these vinyl blocks. 00:20:56.813 --> 00:20:58.560 You'll see a video clip in a moment. 00:20:58.560 --> 00:21:00.000 And these vinyl clocks have-- 00:21:00.000 --> 00:21:03.072 blocks have been rigged by us so that they range in weight. 00:21:03.072 --> 00:21:05.030 There's five of them, they're different colors, 00:21:05.030 --> 00:21:06.569 so infants can keep track of them. 00:21:06.569 --> 00:21:08.610 During training, what happens is the experimenter 00:21:08.610 --> 00:21:10.320 plays a game with an infant where 00:21:10.320 --> 00:21:13.860 they get them to drop each block into a bucket. 00:21:13.860 --> 00:21:16.590 Babies like to do that, it makes a cool noise, right? 00:21:16.590 --> 00:21:19.090 And, really, this training phase serves two purposes. 00:21:19.090 --> 00:21:20.580 The first purpose that it serves is 00:21:20.580 --> 00:21:23.460 we want infants to learn how much each block weighs. 00:21:23.460 --> 00:21:24.960 The second purpose that it serves 00:21:24.960 --> 00:21:27.000 is we want to be able to record what 00:21:27.000 --> 00:21:30.000 is the heaviest block that infants are capable of lifting. 00:21:30.000 --> 00:21:31.350 All right. 00:21:31.350 --> 00:21:32.850 In the test phase, as I told you, 00:21:32.850 --> 00:21:34.680 the experimenter's on the opposite side of the room, 00:21:34.680 --> 00:21:36.120 she's building a block tower, she 00:21:36.120 --> 00:21:38.072 needs a block to complete it. 00:21:38.072 --> 00:21:40.530 There's a single target block available to infants and what 00:21:40.530 --> 00:21:42.510 varies between our two conditions 00:21:42.510 --> 00:21:43.920 is the weight of that block. 00:21:43.920 --> 00:21:46.590 So for half of the babies, the lightest block of the training 00:21:46.590 --> 00:21:48.169 blocks is left behind. 00:21:48.169 --> 00:21:49.710 And for the other half of the babies, 00:21:49.710 --> 00:21:52.080 the heaviest block that infants are capable of lifting 00:21:52.080 --> 00:21:53.400 has been left behind. 00:21:53.400 --> 00:21:55.226 So we're contrasting effort here in terms 00:21:55.226 --> 00:21:56.850 of the weight of the block that infants 00:21:56.850 --> 00:22:01.960 have to carry across the room to help the experimenter. 00:22:01.960 --> 00:22:04.050 So we're looking at infants block retrievals. 00:22:04.050 --> 00:22:06.570 The other thing that we recorded was a parent report 00:22:06.570 --> 00:22:07.900 of infants walking experience. 00:22:07.900 --> 00:22:10.800 So these are 18-month-old infants, they can all walk. 00:22:10.800 --> 00:22:12.990 On average, they've been walking for six months 00:22:12.990 --> 00:22:14.970 so they're all experienced walkers. 00:22:14.970 --> 00:22:16.470 But there's individual variability 00:22:16.470 --> 00:22:19.290 in terms of how long they've been walking for. 00:22:19.290 --> 00:22:20.470 So why was this important? 00:22:20.470 --> 00:22:21.750 Well, here was our underlying logic. 00:22:21.750 --> 00:22:23.833 Imagine that you and a friend are going on a hike, 00:22:23.833 --> 00:22:26.550 you're both equally strong, you can both lift 60 pounds. 00:22:26.550 --> 00:22:28.260 But your friend is an expert hiker 00:22:28.260 --> 00:22:29.972 and you're a novice hiker, right? 00:22:29.972 --> 00:22:32.430 And you both have to carry a 60 pound backpack up the hill. 00:22:32.430 --> 00:22:35.244 Well, despite the fact that you might both be equally strong, 00:22:35.244 --> 00:22:36.660 if you're the novice hiker, that's 00:22:36.660 --> 00:22:38.451 probably going to be more effortful for you 00:22:38.451 --> 00:22:40.830 to get that backpack up the hill than it is going to be 00:22:40.830 --> 00:22:42.850 for your friend or your buddy. 00:22:42.850 --> 00:22:44.700 So we had a particular prediction 00:22:44.700 --> 00:22:48.060 that what we would see is a relationship between parent 00:22:48.060 --> 00:22:51.120 reporter walking experience, and infants likelihood do this-- 00:22:51.120 --> 00:22:53.160 likelihood to help the experimenter by carrying 00:22:53.160 --> 00:22:56.040 the block across the room, and that this would be selective, 00:22:56.040 --> 00:23:00.780 or at least stronger, for the high effort condition. 00:23:00.780 --> 00:23:02.070 OK. 00:23:02.070 --> 00:23:04.140 So let me show you a couple little video clips 00:23:04.140 --> 00:23:07.064 here so you can get a flavor of the procedure. 00:23:07.064 --> 00:23:08.730 This is just showing you the test phase, 00:23:08.730 --> 00:23:10.919 so it's exerted from the test phase. 00:23:10.919 --> 00:23:12.960 There's one thing I want to explain a little bit. 00:23:12.960 --> 00:23:17.765 So you can see up here there's this striped bucket here. 00:23:17.765 --> 00:23:19.140 And the reason that we have there 00:23:19.140 --> 00:23:21.514 is-- that there is because we want the experimenter to be 00:23:21.514 --> 00:23:23.670 unaware of the target block that is left behind, 00:23:23.670 --> 00:23:25.860 so they're naive to the infant's condition. 00:23:25.860 --> 00:23:27.780 It looks like from the infants' perspective that they can see 00:23:27.780 --> 00:23:29.180 the target block, but they actually can't. 00:23:29.180 --> 00:23:30.420 They don't know if they're in the high or low effort 00:23:30.420 --> 00:23:31.260 condition. 00:23:31.260 --> 00:23:34.440 So this is the baby who is tested in the low effort 00:23:34.440 --> 00:23:36.952 condition. 00:23:36.952 --> 00:23:37.618 [VIDEO PLAYBACK] 00:23:37.618 --> 00:23:40.500 I'm going to use these blocks to make a tower. 00:23:40.500 --> 00:23:42.010 These blocks can go here. 00:23:45.020 --> 00:23:47.976 This one can go here. 00:23:47.976 --> 00:23:50.560 And this block can go-- 00:23:50.560 --> 00:23:53.140 oh, no. 00:23:53.140 --> 00:23:58.010 Oh, no, I'm missing the block I need to finish my tower. 00:23:58.010 --> 00:23:59.994 I'm missing my block. 00:23:59.994 --> 00:24:02.994 Ah, oh, there it is, Joelle look. 00:24:02.994 --> 00:24:06.140 The block got moved on your blanket. 00:24:06.140 --> 00:24:09.048 Can you bring me the blocks so I can finish my tower? 00:24:14.327 --> 00:24:14.910 [END PLAYBACK] 00:24:14.910 --> 00:24:15.459 All right. 00:24:15.459 --> 00:24:17.000 Sorry, we exerted a little bit early. 00:24:17.000 --> 00:24:18.666 He goes over and he gives her the block. 00:24:18.666 --> 00:24:19.410 OK. 00:24:19.410 --> 00:24:19.910 OK. 00:24:19.910 --> 00:24:21.890 Now let's watch a baby in the high effort condition. 00:24:21.890 --> 00:24:23.840 Remember, the only difference between these two conditions 00:24:23.840 --> 00:24:26.210 is the weight of the block that's been left behind. 00:24:26.210 --> 00:24:27.412 OK. 00:24:27.412 --> 00:24:28.344 [VIDEO PLAYBACK] 00:24:28.344 --> 00:24:32.275 I'm going to use these blocks to make a tower These blocks can 00:24:32.275 --> 00:24:34.430 go here. 00:24:34.430 --> 00:24:37.150 This one can go here. 00:24:37.150 --> 00:24:39.548 And this one can go-- 00:24:39.548 --> 00:24:41.908 oh, no. 00:24:41.908 --> 00:24:46.462 Oh, no, I'm missing the block I need to finish my tower. 00:24:46.462 --> 00:24:48.872 I'm missing my block. 00:24:48.872 --> 00:24:50.318 Ah, oh. 00:24:50.318 --> 00:24:51.764 There it is, Rose. 00:24:51.764 --> 00:24:54.360 The block got left on your blanket. 00:24:54.360 --> 00:24:57.140 Can you bring me the block so I can finish my tower? 00:25:00.125 --> 00:25:07.035 [LAUGHTER] Can you bring me the block? 00:25:11.936 --> 00:25:16.972 Rose, can you bring me the block so I can finish my tower? 00:25:16.972 --> 00:25:17.472 No. 00:25:24.307 --> 00:25:24.890 [END PLAYBACK] 00:25:24.890 --> 00:25:26.430 So it's a little hard to hear what she was saying, 00:25:26.430 --> 00:25:28.700 but if you couldn't hear it, she was saying, no, thank you. 00:25:28.700 --> 00:25:29.240 So she said, no. 00:25:29.240 --> 00:25:29.770 No, thank you. 00:25:29.770 --> 00:25:30.353 No, thank you. 00:25:30.353 --> 00:25:31.760 OK. 00:25:31.760 --> 00:25:34.470 So that's a-- pretty illustrative of the procedure. 00:25:34.470 --> 00:25:34.970 OK. 00:25:34.970 --> 00:25:35.890 So what did we find? 00:25:35.890 --> 00:25:38.161 So here's infants' rates of helping in the low effort 00:25:38.161 --> 00:25:38.660 condition. 00:25:38.660 --> 00:25:40.880 In the high effort condition what you can see. 00:25:40.880 --> 00:25:42.440 So infants help much more frequently 00:25:42.440 --> 00:25:45.055 in the low effort condition than in a high effort condition. 00:25:45.055 --> 00:25:46.430 Here's what we found with respect 00:25:46.430 --> 00:25:47.900 to infants' walking experience. 00:25:47.900 --> 00:25:50.930 A walking experience, how long an infant has been walking 00:25:50.930 --> 00:25:53.390 predicts infants' likelihood of helping in the high effort 00:25:53.390 --> 00:25:54.470 condition. 00:25:54.470 --> 00:25:57.115 And what this tells us is that for each month 00:25:57.115 --> 00:25:58.490 of additional walking experience, 00:25:58.490 --> 00:26:00.950 infants are twice as likely to help. 00:26:00.950 --> 00:26:03.170 Now, what we can see here is that infants 00:26:03.170 --> 00:26:05.690 are less likely to help under high effort conditions, right? 00:26:05.690 --> 00:26:07.910 So infants prosocial behavior is influenced 00:26:07.910 --> 00:26:11.100 by the effort related costs of prosocial responding. 00:26:11.100 --> 00:26:14.430 And a critic, I guess, could say, 00:26:14.430 --> 00:26:16.820 well, maybe it's that-- it's not that infants 00:26:16.820 --> 00:26:18.920 are going by the effort, it's maybe 00:26:18.920 --> 00:26:21.600 that they're not able to help in the high effort condition. 00:26:21.600 --> 00:26:23.990 We don't think that that's the case, because infants have 00:26:23.990 --> 00:26:26.960 given us evidence that they're capable of lifting that block, 00:26:26.960 --> 00:26:27.480 right? 00:26:27.480 --> 00:26:29.854 That they're later-- later tested with in the high effort 00:26:29.854 --> 00:26:30.395 condition. 00:26:30.395 --> 00:26:31.895 But the next condition I'll show you 00:26:31.895 --> 00:26:35.250 will also kind of speak to that. 00:26:35.250 --> 00:26:37.550 And the important-- another important thing 00:26:37.550 --> 00:26:40.150 to recognize here is that infants 00:26:40.150 --> 00:26:43.280 seem to be recognizing these costs at an objective level. 00:26:43.280 --> 00:26:45.500 I think Laura called this in her talk an agent 00:26:45.500 --> 00:26:46.700 independent level, right? 00:26:46.700 --> 00:26:49.280 As a function of the circumstances of the situation, 00:26:49.280 --> 00:26:50.240 right? 00:26:50.240 --> 00:26:52.520 And they're also recognizing costs 00:26:52.520 --> 00:26:54.200 that at a more subjective level in terms 00:26:54.200 --> 00:26:56.000 of their own capabilities and how that 00:26:56.000 --> 00:26:57.440 influences the particular cost. 00:26:57.440 --> 00:26:59.690 In this case, it's their amount of walking experience, 00:26:59.690 --> 00:27:02.450 how expert a walker they are. 00:27:02.450 --> 00:27:04.850 OK. 00:27:04.850 --> 00:27:07.040 So what we wanted to do next is to find out 00:27:07.040 --> 00:27:09.230 whether if when infants are presented 00:27:09.230 --> 00:27:11.277 with these high effortful helping situations, 00:27:11.277 --> 00:27:12.860 whether infants helping behavior would 00:27:12.860 --> 00:27:16.160 vary as a function of the motivational benefits 00:27:16.160 --> 00:27:18.900 of prosocial responding. 00:27:18.900 --> 00:27:20.930 Now, it's been pretty firmly established 00:27:20.930 --> 00:27:23.180 that early prosocial responding appears to be 00:27:23.180 --> 00:27:24.750 immune to extrinsic rewards. 00:27:24.750 --> 00:27:26.270 So what that means is if you test 00:27:26.270 --> 00:27:27.936 a baby in one of these helping paradigms 00:27:27.936 --> 00:27:29.889 and you say, good job, way to go, good job. 00:27:29.889 --> 00:27:31.430 That's actually not going to increase 00:27:31.430 --> 00:27:32.846 their subsequent helping behavior. 00:27:32.846 --> 00:27:35.701 If anything, it will decrease it. 00:27:35.701 --> 00:27:38.360 But that doesn't mean that more intrinsic rewards 00:27:38.360 --> 00:27:39.860 don't influence how infants perform 00:27:39.860 --> 00:27:40.943 on these particular tasks. 00:27:44.030 --> 00:27:46.820 We know from some prior work that infants by this age 00:27:46.820 --> 00:27:49.250 have certain affiliated biases, right? 00:27:49.250 --> 00:27:51.200 They have biases for individuals who 00:27:51.200 --> 00:27:53.300 share their preferences, who share the-- 00:27:53.300 --> 00:27:55.290 who like the same things that the infant likes. 00:27:55.290 --> 00:27:57.140 They prefer to play with those people who-- 00:27:57.140 --> 00:27:59.690 than people who don't like the same thing that they like. 00:27:59.690 --> 00:28:03.110 And they also have-- possess affiliated biases for people 00:28:03.110 --> 00:28:03.860 who could be-- 00:28:03.860 --> 00:28:06.716 said to share sort of in-group member characteristics, right? 00:28:06.716 --> 00:28:08.090 So infants, like people who speak 00:28:08.090 --> 00:28:09.464 in native-- their native language 00:28:09.464 --> 00:28:12.200 over a nonnative language speaker. 00:28:12.200 --> 00:28:13.970 And, of course, these affiliated biases 00:28:13.970 --> 00:28:16.250 might have important functional consequences, right? 00:28:16.250 --> 00:28:19.070 They might be important for cultural learning. 00:28:22.840 --> 00:28:25.380 So what we wanted to know in this next study 00:28:25.380 --> 00:28:28.800 is whether we could kind of push around these intrinsic benefits 00:28:28.800 --> 00:28:30.870 for infants to see if their behavior would 00:28:30.870 --> 00:28:33.599 change under these high effort helping conditions. 00:28:33.599 --> 00:28:35.640 The way that we did this in this particular study 00:28:35.640 --> 00:28:40.530 is prior to the test procedure, the helping task, 00:28:40.530 --> 00:28:42.750 we had infants take part in this little task 00:28:42.750 --> 00:28:44.070 where they were given one-- 00:28:44.070 --> 00:28:44.580 two toys. 00:28:44.580 --> 00:28:45.840 They could choose between the two toys. 00:28:45.840 --> 00:28:47.190 This happened on three different trials, 00:28:47.190 --> 00:28:48.394 different toys each trial. 00:28:48.394 --> 00:28:49.560 Infants would make a choice. 00:28:49.560 --> 00:28:53.010 And then the experimenter would subsequently 00:28:53.010 --> 00:28:56.010 show that she liked one toy and disliked the other toy. 00:28:56.010 --> 00:28:57.720 And the really simple manipulation 00:28:57.720 --> 00:28:59.310 between these two different conditions 00:28:59.310 --> 00:29:02.400 was whether the experimenter liked the same toy as the baby, 00:29:02.400 --> 00:29:04.050 or whether she liked the other toy. 00:29:04.050 --> 00:29:06.420 So did she share the infant's preferences, 00:29:06.420 --> 00:29:08.706 or did she oppose their preferences, right? 00:29:08.706 --> 00:29:10.330 And we would think in terms of the data 00:29:10.330 --> 00:29:11.910 on infants affiliative biases, that they 00:29:11.910 --> 00:29:13.451 would prefer to interact with someone 00:29:13.451 --> 00:29:16.320 who shares their preferences. 00:29:16.320 --> 00:29:18.570 Infants took part in the same helping task 00:29:18.570 --> 00:29:20.340 as they did in the first experiment. 00:29:20.340 --> 00:29:23.160 To streamline the procedure, we used the medium block weight 00:29:23.160 --> 00:29:26.174 that infants have been capable of lifting in the first study. 00:29:26.174 --> 00:29:28.590 The other thing that we did is we added a post-test phase. 00:29:28.590 --> 00:29:31.380 So we excluded any infants who were not 00:29:31.380 --> 00:29:34.350 capable in the post-test of lifting the target block 00:29:34.350 --> 00:29:35.490 or a heavier block, right? 00:29:35.490 --> 00:29:38.370 So we know for all of these infants in the sample 00:29:38.370 --> 00:29:39.690 that they can lift the block. 00:29:39.690 --> 00:29:43.084 The question is, do they help the experimenter. 00:29:46.491 --> 00:29:46.990 OK. 00:29:46.990 --> 00:29:48.760 So we again looked at infants' helping behavior, 00:29:48.760 --> 00:29:50.540 we looked at their walking experience. 00:29:50.540 --> 00:29:51.850 The other thing that we did in the study 00:29:51.850 --> 00:29:54.280 is we looked at infants helping as a function of the response 00:29:54.280 --> 00:29:54.780 period. 00:29:54.780 --> 00:29:56.435 Whether helping occurred in the-- 00:29:56.435 --> 00:29:58.810 rates of helping in the first half of the response period 00:29:58.810 --> 00:30:01.630 versus the rates of helping overall in the response period. 00:30:01.630 --> 00:30:03.220 And our motivation for doing this 00:30:03.220 --> 00:30:05.320 is that we thought that if there are differences 00:30:05.320 --> 00:30:06.819 in the degree of motivation to help, 00:30:06.819 --> 00:30:09.700 you might see early differences in the response period, right? 00:30:09.700 --> 00:30:11.620 So early on, infants might differentiate 00:30:11.620 --> 00:30:13.100 across the conditions. 00:30:13.100 --> 00:30:15.410 But these might attenuate over time. 00:30:15.410 --> 00:30:17.560 One thing I forgot to mention is that in the course 00:30:17.560 --> 00:30:19.540 of the response period, infants receive 00:30:19.540 --> 00:30:23.260 prompts at certain intervals in order to say, 00:30:23.260 --> 00:30:24.910 can you get me the block, right? 00:30:24.910 --> 00:30:26.590 So the question is with these prompts 00:30:26.590 --> 00:30:30.840 will any early differences that we see attenuate over time? 00:30:30.840 --> 00:30:31.377 OK. 00:30:31.377 --> 00:30:32.460 So here's what we can see. 00:30:32.460 --> 00:30:33.850 This is the first half of the response period. 00:30:33.850 --> 00:30:35.600 Infants in the shared preference condition 00:30:35.600 --> 00:30:38.530 are significantly more likely to help the experimenter 00:30:38.530 --> 00:30:41.350 than infants in the nonshared preference condition, right? 00:30:41.350 --> 00:30:43.690 So when there are intrinsic rewards associated 00:30:43.690 --> 00:30:45.310 with engaging in high effort behavior, 00:30:45.310 --> 00:30:47.670 infants are more likely to help the experimenter. 00:30:47.670 --> 00:30:49.450 And the other thing that we saw is 00:30:49.450 --> 00:30:51.970 that infants walking experience significantly 00:30:51.970 --> 00:30:55.870 predicts helping behavior in the nonshared preference condition. 00:30:55.870 --> 00:30:58.630 So when the motivational benefits are low, 00:30:58.630 --> 00:31:01.990 these subjective costs seem to exert a stronger-- 00:31:01.990 --> 00:31:04.980 a stronger role, have a stronger predictive value, 00:31:04.980 --> 00:31:07.819 than when the motivational consequences-- or, sorry, 00:31:07.819 --> 00:31:09.110 motivational benefits are high. 00:31:11.521 --> 00:31:14.020 And then here, this just shows you infants' helping behavior 00:31:14.020 --> 00:31:16.180 but, now, as a function of the overall response period. 00:31:16.180 --> 00:31:18.180 You can see they're still numerically different, 00:31:18.180 --> 00:31:19.870 but they start to come together, right? 00:31:19.870 --> 00:31:21.520 So the differences are really driven 00:31:21.520 --> 00:31:23.860 by what's happening early in the response period. 00:31:27.440 --> 00:31:28.087 OK. 00:31:28.087 --> 00:31:30.170 So these findings suggest that infants willingness 00:31:30.170 --> 00:31:31.730 to engage in high effort-- 00:31:31.730 --> 00:31:33.680 high cost helping is motivated or affected 00:31:33.680 --> 00:31:35.867 by intrinsic motivational factors. 00:31:35.867 --> 00:31:38.450 Infants are more likely to carry a heavy block to help someone 00:31:38.450 --> 00:31:39.740 who shares their preference. 00:31:39.740 --> 00:31:41.156 One thing I want to point out here 00:31:41.156 --> 00:31:43.426 is that these findings help us sort of 00:31:43.426 --> 00:31:45.800 interpret what's going on in the first experiment, right? 00:31:45.800 --> 00:31:48.140 If the first experiment was explained by the fact 00:31:48.140 --> 00:31:50.656 that it's a lack of ability versus a lack of effort, 00:31:50.656 --> 00:31:52.280 we shouldn't get these findings, right? 00:31:52.280 --> 00:31:54.620 Because the effort is equivalent across these two conditions 00:31:54.620 --> 00:31:55.119 here. 00:31:55.119 --> 00:32:00.625 And what simply varies are the kind of motivational benefits. 00:32:00.625 --> 00:32:01.432 OK. 00:32:01.432 --> 00:32:03.140 So, now, I want to tell you about a study 00:32:03.140 --> 00:32:05.885 that we're just in the middle of conducting. 00:32:05.885 --> 00:32:07.760 I think it's really exciting and interesting. 00:32:07.760 --> 00:32:08.820 I'd be curious to get your thoughts. 00:32:08.820 --> 00:32:10.760 So we're literally mid data collection, 00:32:10.760 --> 00:32:12.590 but I think I have enough data to tell you 00:32:12.590 --> 00:32:15.110 what's going on so far. 00:32:15.110 --> 00:32:17.630 So, now, we're trying to expand the scope of benefits 00:32:17.630 --> 00:32:19.400 that we're looking at, right? 00:32:19.400 --> 00:32:21.720 And as we sort of alluded to earlier, 00:32:21.720 --> 00:32:23.530 we don't-- really don't know as of yet, 00:32:23.530 --> 00:32:25.940 or we don't know very much, about what cost counts 00:32:25.940 --> 00:32:27.970 as a cost and a benefit for infants, right? 00:32:27.970 --> 00:32:29.345 That's something that we actually 00:32:29.345 --> 00:32:31.509 have to figure out to determine empirically. 00:32:31.509 --> 00:32:33.050 There's been some recent studies that 00:32:33.050 --> 00:32:35.510 have shown that three- and four-year-olds, perhaps 00:32:35.510 --> 00:32:38.540 paradoxically, when they're tested in sharing tasks, 00:32:38.540 --> 00:32:41.450 are more likely to share with a rich recipient 00:32:41.450 --> 00:32:43.460 than a poor recipient, right? 00:32:43.460 --> 00:32:45.740 And that is paradoxical in the sense that, of course, 00:32:45.740 --> 00:32:49.160 the rich recipient has less of a need than the poor recipient. 00:32:49.160 --> 00:32:52.550 But, perhaps, unsurprising in the sense 00:32:52.550 --> 00:32:54.470 that there's something self-serving, right, 00:32:54.470 --> 00:32:56.810 like it might be in your self-interest to affiliate 00:32:56.810 --> 00:32:59.018 with people who have a lot of resources versus people 00:32:59.018 --> 00:33:00.230 who have few resources. 00:33:00.230 --> 00:33:03.080 In our study, what we did, is before infants got the helping 00:33:03.080 --> 00:33:05.660 task, we demonstrated to them that one individual 00:33:05.660 --> 00:33:08.420 had more resources than the other individual. 00:33:08.420 --> 00:33:09.890 It's a really simple manipulation. 00:33:09.890 --> 00:33:11.690 What they did is they saw two individuals are 00:33:11.690 --> 00:33:12.481 sitting at a table. 00:33:12.481 --> 00:33:14.810 They both had these like transparent fish bowl looking 00:33:14.810 --> 00:33:18.110 balls, and on each trial they have different goods 00:33:18.110 --> 00:33:19.520 in the fish bowls. 00:33:19.520 --> 00:33:23.030 So what happens is that one individual always 00:33:23.030 --> 00:33:24.297 has lots of stuff, right? 00:33:24.297 --> 00:33:26.380 On one trial it's animal crackers, the other trial 00:33:26.380 --> 00:33:27.650 it's these cool little balls. 00:33:27.650 --> 00:33:31.280 The third trial it's these cool, flashing little blingy rings. 00:33:31.280 --> 00:33:33.800 And the other person has very few. 00:33:33.800 --> 00:33:35.930 But they both do exactly the same thing 00:33:35.930 --> 00:33:36.980 during this first phase. 00:33:36.980 --> 00:33:38.530 What they do is they take turns-- 00:33:38.530 --> 00:33:40.280 we counterbalance everything, of course-- 00:33:40.280 --> 00:33:42.260 they pull out three objects one at a time 00:33:42.260 --> 00:33:46.700 and, they say, hey, baby, look at all my toys, right? 00:33:46.700 --> 00:33:49.390 So they're both doing the same thing, exactly the same thing. 00:33:49.390 --> 00:33:53.690 What differs is the kind of resource contacts, right? 00:33:53.690 --> 00:33:55.050 One of them has a lot of stuff. 00:33:55.050 --> 00:33:57.240 One of them only has three things, right? 00:33:57.240 --> 00:33:58.670 And we do that on repeated trials, 00:33:58.670 --> 00:34:00.000 because we're trying to give babies 00:34:00.000 --> 00:34:02.240 the impression that, generally, this person has more 00:34:02.240 --> 00:34:03.945 stuff than the other person. 00:34:03.945 --> 00:34:05.300 OK. 00:34:05.300 --> 00:34:07.197 So then we test infants in the helping task. 00:34:07.197 --> 00:34:09.530 This helping task is a little bit different than the one 00:34:09.530 --> 00:34:11.196 I just told you about, because now we're 00:34:11.196 --> 00:34:13.500 pitting these two experimenters against one another. 00:34:13.500 --> 00:34:16.280 The experimenters in the helping task have equivalent need. 00:34:16.280 --> 00:34:18.409 They both, like Miranda was doing earlier, 00:34:18.409 --> 00:34:19.701 are building this tower, right? 00:34:19.701 --> 00:34:21.450 They're missing a block, they need a block 00:34:21.450 --> 00:34:22.850 to complete their tower, right? 00:34:22.850 --> 00:34:24.020 The only thing that differentiates 00:34:24.020 --> 00:34:25.730 the experimenters is what happened previously. 00:34:25.730 --> 00:34:27.688 One person had a lot of stuff, the other person 00:34:27.688 --> 00:34:29.840 didn't have very much stuff. 00:34:29.840 --> 00:34:32.239 And the other thing that we're manipulating here 00:34:32.239 --> 00:34:35.420 is whether the infant has to engage 00:34:35.420 --> 00:34:39.830 in equally effortful actions to help the two experimenters, 00:34:39.830 --> 00:34:42.560 or whether helping one of the experimenters 00:34:42.560 --> 00:34:44.000 is more effortful. 00:34:44.000 --> 00:34:45.920 And the way that we've operationalized this so 00:34:45.920 --> 00:34:50.960 far in this study is by varying how long the baby has to walk. 00:34:50.960 --> 00:34:53.600 So, in one case, the person is within a few feet, 00:34:53.600 --> 00:34:55.440 in the other case, they're across the room. 00:34:55.440 --> 00:34:57.560 OK. 00:34:57.560 --> 00:34:59.990 So let me show you the data, first, for the equal effort 00:34:59.990 --> 00:35:00.580 condition. 00:35:00.580 --> 00:35:02.660 So these are-- this is-- 00:35:02.660 --> 00:35:06.410 what this graph shows you is who the baby is helping. 00:35:06.410 --> 00:35:09.950 And what you can see here is when effort is equivalent, 00:35:09.950 --> 00:35:12.290 infants are systematically helping the person 00:35:12.290 --> 00:35:13.490 who has more resources. 00:35:13.490 --> 00:35:16.346 They're helping the rich experimenter, right? 00:35:16.346 --> 00:35:17.720 So now the question becomes, what 00:35:17.720 --> 00:35:19.504 happens in cases of unequal effort? 00:35:19.504 --> 00:35:21.170 And as I said, this data is still coming 00:35:21.170 --> 00:35:23.086 and we're still testing this, so the condition 00:35:23.086 --> 00:35:26.150 that we started with, given that we have this initial pattern, 00:35:26.150 --> 00:35:28.760 is the condition where the rich experimenter is the one you 00:35:28.760 --> 00:35:30.021 have to walk a long way to. 00:35:30.021 --> 00:35:31.520 And the poor experimenter is the one 00:35:31.520 --> 00:35:34.432 you have to walk a short way to. 00:35:34.432 --> 00:35:35.390 And here's what we see. 00:35:35.390 --> 00:35:37.680 It flips. 00:35:37.680 --> 00:35:42.080 So I think what this suggests is that infants are both weighing 00:35:42.080 --> 00:35:45.080 the costs of the action they have to perform, 00:35:45.080 --> 00:35:48.770 and the intrinsic motivational benefits as defined 00:35:48.770 --> 00:35:50.240 by these sort of things that might 00:35:50.240 --> 00:35:52.370 be important for social affiliation. 00:35:55.050 --> 00:35:55.550 OK. 00:35:55.550 --> 00:35:57.008 So what implications does this have 00:35:57.008 --> 00:35:59.182 for infants' prosocial behavior? 00:35:59.182 --> 00:36:00.890 Well, it suggests that it may be the case 00:36:00.890 --> 00:36:02.750 that cost benefit analyses underlie 00:36:02.750 --> 00:36:04.070 infants prosocial behavior. 00:36:04.070 --> 00:36:06.890 In particular, their helping behavior. 00:36:06.890 --> 00:36:09.304 And I also want to take us back to two of the questions 00:36:09.304 --> 00:36:10.220 that I raised earlier. 00:36:10.220 --> 00:36:12.680 One was about the selective nature 00:36:12.680 --> 00:36:15.830 of early prosocial behavior, the strategic nature. 00:36:15.830 --> 00:36:19.160 And the other was about the underlying motivation. 00:36:19.160 --> 00:36:22.020 So think in terms of the selective strategic question, 00:36:22.020 --> 00:36:25.400 on the one hand, we can say, fairly early on at 18 months, 00:36:25.400 --> 00:36:28.340 infants' prosocial behavior is strategic in the sense 00:36:28.340 --> 00:36:30.350 that what they seem to be doing is 00:36:30.350 --> 00:36:33.330 minimizing costs and maximizing motivational benefits. 00:36:36.510 --> 00:36:38.300 And in terms of the motivation, I 00:36:38.300 --> 00:36:39.860 think what these findings tell us, 00:36:39.860 --> 00:36:42.170 and this is not to say that infants are never motivated 00:36:42.170 --> 00:36:43.586 by empathic concern, they're never 00:36:43.586 --> 00:36:45.270 motivated by other people's needs, 00:36:45.270 --> 00:36:47.620 but there are other things that come into play here. 00:36:47.620 --> 00:36:50.120 So infants' underlying motivation to help 00:36:50.120 --> 00:36:52.910 is influenced by a tendency to want to affiliate 00:36:52.910 --> 00:36:56.750 with particular individuals. 00:36:56.750 --> 00:36:57.377 OK. 00:36:57.377 --> 00:36:59.960 So I told you a little bit about infants registration of costs 00:36:59.960 --> 00:37:02.757 in the actions of other people, their use of costs and benefits 00:37:02.757 --> 00:37:04.340 to guide their own prosocial behavior. 00:37:04.340 --> 00:37:08.030 I just want to close by kind of raising some questions that I 00:37:08.030 --> 00:37:11.010 think we should be interested in pursuing in the future. 00:37:11.010 --> 00:37:11.510 OK. 00:37:11.510 --> 00:37:12.920 So this came up earlier, right? 00:37:12.920 --> 00:37:14.545 So one thing that we have to understand 00:37:14.545 --> 00:37:16.040 to understand infants' behavior is 00:37:16.040 --> 00:37:18.200 to understand what acts as a cost for infants 00:37:18.200 --> 00:37:19.984 and what acts as a benefit for infants. 00:37:19.984 --> 00:37:22.400 And I think the thing that's really important to point out 00:37:22.400 --> 00:37:26.000 here is it won't necessarily be what we think as adults, right? 00:37:26.000 --> 00:37:28.322 It won't be intuitive to us, right? 00:37:28.322 --> 00:37:29.780 And the classic example that we can 00:37:29.780 --> 00:37:32.720 think about is, you know, you buy your child this toy, 00:37:32.720 --> 00:37:34.280 you bring it home from the store, 00:37:34.280 --> 00:37:36.830 you're so excited to give your child this cool snazzy toy, 00:37:36.830 --> 00:37:39.530 and all they want to do is play with the box, right? 00:37:39.530 --> 00:37:42.414 So what that shows us is we're not good models, necessarily. 00:37:42.414 --> 00:37:44.330 We have to kind of determine this empirically. 00:37:44.330 --> 00:37:49.550 We can't necessarily use our own intuitions to figure this out. 00:37:49.550 --> 00:37:52.190 Another question is how are costs read, right? 00:37:52.190 --> 00:37:54.000 So in the first study I showed you 00:37:54.000 --> 00:37:56.270 that infants' experience potentially is important, 00:37:56.270 --> 00:37:58.869 or factors that gait infants' experience, right? 00:37:58.869 --> 00:38:00.410 But that's in a situation where there 00:38:00.410 --> 00:38:03.220 aren't a lot of observable cues to effort. 00:38:03.220 --> 00:38:04.970 So I think it may be the case that there's 00:38:04.970 --> 00:38:06.350 some variability here. 00:38:06.350 --> 00:38:09.080 Some costs infants may require experience 00:38:09.080 --> 00:38:12.530 with in order to figure out what is the cost, right? 00:38:12.530 --> 00:38:13.709 How much of a cost is this? 00:38:13.709 --> 00:38:16.250 And maybe there are other costs that infants can more readily 00:38:16.250 --> 00:38:19.250 read from the get go. 00:38:19.250 --> 00:38:21.390 And then, finally, I think at some point, 00:38:21.390 --> 00:38:23.390 we need to ask whether infants and, potentially, 00:38:23.390 --> 00:38:26.622 children are sensitive to other types of costs beyond effort. 00:38:26.622 --> 00:38:29.080 Also, if they have a kind of higher level category of cost. 00:38:29.080 --> 00:38:31.490 So one thing that's really interesting in the literature 00:38:31.490 --> 00:38:33.500 on nonhuman animals is that there are just 00:38:33.500 --> 00:38:36.260 so simple neural systems that are responsible 00:38:36.260 --> 00:38:38.210 for effort reward decision-making, 00:38:38.210 --> 00:38:40.130 and for delay reward decision-making. 00:38:40.130 --> 00:38:42.350 But, obviously, we, as adults, can group these things 00:38:42.350 --> 00:38:44.660 together, or I wouldn't be able to give this talk today, 00:38:44.660 --> 00:38:47.030 and Laura wouldn't have been able to give her talk today. 00:38:47.030 --> 00:38:49.160 So one of the things we have to start to understand 00:38:49.160 --> 00:38:51.530 is when did those things kind of come together 00:38:51.530 --> 00:38:53.940 in service of this larger category of cost. 00:38:53.940 --> 00:38:54.440 OK. 00:38:54.440 --> 00:38:59.200 So I'm going to stop there and ask for questions.