Emotional Movement Kinematics Guide Twelve-Month-Olds' Visual, but Not Manual, Exploration

Abstract

The ability to recognize and act on others' emotions is crucial for navigating social interactions successfully and learning about the world. One way in which others' emotions are observable is through their movement kinematics. Movement information is available even at a distance or when an individual's face is not visible. Infants have been shown to be sensitive to emotions in movement kinematics of transporting actions, like moving an object from one to another place. However, it is still unknown whether they associate the manipulated object with the emotions contained in moving it, and whether they use this information to guide their own exploration of this object. In this study, 12-month-old infants watched actors transporting two toys with positive or negative emotional valence. Then, infants were given the possibility to interact with the same toys. We expected the infants to look at and touch the toy handled in a positive manner more, compared to the toy handled in a negative manner. Our results showed that infants looked at the positive toys more than at the negative toys, but that infants touched both toys for the same amount of time. Also, there was no difference in which toy they manually explored first.

Keywords: emotion; emotion processing; exploration; kinematics; movement.

FIGURE 1

Pictures of the toys used in the study in stimulus and behavioral testing phases.

FIGURE 2

Series of frames from an example stimulus video.

FIGURE 3

(a) Side view of the experimental set up with a chair for parents and infants to sit, a table with a mounted webcam under the stimuli presentation screen with built‐in eye tracker, and a mirror that enabled recording of the screen during the trial. (b) The view from the webcam during stimulus presentation.

FIGURE 4

The figure illustrates the sequence of an example trial, including still images of the attention getter, the stimulus videos and a recording from the study showing a child grasping a toy.

FIGURE 5

A pirate plot of the percentage of looking time out of total trial time [%] during trial 1 and trial 2; each dot represents a data point, the bold black horizontal line represents the mean of each condition, and the semi‐transparent box shows the 89% highest density interval (HDI) around the mean.

FIGURE 6

A pirate plot of the percentage of touching out of total trial time during trial 1 and trial 2; each dot represents a data point, the bold black horizontal line represents the mean of each condition, and the semi‐transparent box shows the 89% highest density interval (HDI) around the mean. Some participants did not touch any toy during a trial (0%).

FIGURE 7

A pirate plot of the proportion of looking at positive and negative affect toys out of the total looking time during the trial; each dot represents a data point, the bold black horizontal line represents the mean of each condition, and the semi‐transparent box shows the 89% highest density interval (HDI) around the mean. Please note: a value of 1 means the participant looked at the toy for 100% of the time they looked at any toy during a trial, not of the total trial time.

FIGURE 8

A pirate plot of the proportion of touching positive and negative affect toys out of the total touching time during the trial; each dot represents a data point, the bold black horizontal line represents the mean of each condition, and the semi‐transparent box shows the 89% highest density interval (HDI) around the mean. A value of 1 means the toy was touched for 100% of the time when any toy was touched during a trial, not of the total trial time.

FIGURE 9

(a) A stacked bar plot of participants' first touch towards positively and negatively valenced toys on two test trials with percentages (%) of each choice. (b) The prior and posterior distribution of the population proportion θ for the Bayesian binomial test on the proportion of the first touch to positive toy difference from chance level (50%) for the first test trial the plot shows the estimate of the population proportion θ after updating prior knowledge with data. The gray dots indicate the density values of the prior and posterior distributions at test value. The dot being higher on the posterior than on the prior distribution shows evidence for the null hypothesis. (c) Analogously to the posterior distribution of the first trial, the posterior distribution for the second test trial is reflecting the evidence for the null hypothesis as the distance between the gray dots.