Inferred goal for mothers and infants.

<p>Shown are the proportion of mothers and infants who, according to our Bayesian model, exhibit behavior consistent with a goal of maximizing time spent in a particular smile configuration.</p

Infants Time Their Smiles to Make Their Moms Smile

<div><p>One of the earliest forms of interaction between mothers and infants is smiling games. While the temporal dynamics of these games have been extensively studied, they are still not well understood. Why do mothers and infants time their smiles the way they do? To answer this question we applied methods from control theory, an approach frequently used in robotics, to analyze and synthesize goal-oriented behavior. The results of our analysis show that by the time infants reach 4 months of age both mothers and infants time their smiles in a purposeful, goal-oriented manner. In our study, mothers consistently attempted to maximize the time spent in mutual smiling, while infants tried to maximize mother-only smile time. To validate this finding, we ported the smile timing strategy used by infants to a sophisticated child-like robot that automatically perceived and produced smiles while interacting with adults. As predicted, this strategy proved successful at maximizing adult-only smile time. The results indicate that by 4 months of age infants interact with their mothers in a goal-oriented manner, utilizing a sophisticated understanding of timing in social interactions. Our work suggests that control theory is a promising technique for both analyzing complex interactive behavior and providing new insights into the development of social communication.</p></div

Comparison of Infant and Mother Goals.

<p>Means of the probability distributions of potential mother and infant goals. Error bars are 95% confidence intervals of the mean.</p

PlosOne_DR_Data

This .mat file includes experimental data (data{i} for subject i, in which data{i}.mg for task 1 and data{i}.ss for task 2), and model output of sensorimotor speed and motivation

Goal stopping position and motivation estimated from Task 2.

<p>a. Average goal stopping position across blocks as a function of BDI. b. Goal stopping position over time in three blocks in four depressive groups. c. Estimated motivation for each subject, taking into consideration of individual differences in both sensorimotor speed and goal state. d. Estimated motivation for each subject, not considering individual differences in sensorimotor speed and goal state.</p

Fixed effects for model predicting goal stop distance.

<p>Fixed effects for model predicting goal stop distance.</p

Sensorimotor speed.

<p>a. Sensory speed. b. Motor speed.</p

Experiment paradigm.

<p>In Task1 (stop-sign), subjects were instructed to drive the car to the stop-sign as quickly as possible and stop as close as possible to the sign without crossing the white line. In Task 2 (wall), subjects received the same instructions as in task 1, with the addition that they could not crash into the wall (instead of not crossing the stop-sign). Both tasks have a fixed time window of 6 seconds.</p

The influence of depressed mood on stopping distance in stop-sign and wall condition.

<p>a. Group comparison. P-values are Bonferroni corrected for multiple comparisons. Black line is the target (stop-sign or wall). Blue bars represent the stopping distance of the 3 groups in stop-sign condition and red bars represent that in wall condition, respectively. b. Stopping distance as a function of BDI. Each data point represents each individual’s stopping position relative to the target.</p

PlosOne_Data

Included are the dataset for analyzing and producing the figures included in the manuscript. Please contact [email protected] for detail