The impact of salient action effects on 6-, 7-, and 11-month-olds' goal-predictive gaze shifts for a human grasping action

Abstract

When infants observe a human grasping action, experience-based accounts predict that all infants familiar with grasping actions should be able to predict the goal regardless of additional agency cues such as an action effect. Cue-based accounts, however, suggest that infants use agency cues to identify and predict action goals when the action or the agent is not familiar. From these accounts, we hypothesized that younger infants would need additional agency cues such as a salient action effect to predict the goal of a human grasping action, whereas older infants should be able to predict the goal regardless of agency cues. In three experiments, we presented 6-, 7-, and 11-month-olds with videos of a manual grasping action presented either with or without an additional salient action effect (Exp. 1 and 2), or we presented 7-month-olds with videos of a mechanical claw performing a grasping action presented with a salient action effect (Exp. 3). The 6-month-olds showed tracking gaze behavior, and the 11-month-olds showed predictive gaze behavior, regardless of the action effect. However, the 7-month-olds showed predictive gaze behavior in the action-effect condition, but tracking gaze behavior in the no-action-effect condition and in the action-effect condition with a mechanical claw. The results therefore support the idea that salient action effects are especially important for infants' goal predictions from 7 months on, and that this facilitating influence of action effects is selective for the observation of human hands.

Fig 1. Still frames of the stimulus videos taken from the action-effect condition (upper row) and the no-action-effect condition (middle row) of Experiment 1 and 2 as well as from the claw-action-effect condition (lower row) of Experiment 3.

The squares in the left pictures of the no-action-effect condition and the claw-action-effect condition represent examples of the AOIs used for data analysis (the squares were not visible during the experiment).

Fig 2. Mean gaze-arrival times for the 6-, 11-, and 7-month-olds in the human hand action-effect condition and no-action-effect condition of Experiments 1 and 2, and for the 7-month-olds in the claw-action-effect condition of Experiment 3.

Positive (vs. negative) values represent gaze arrival at the goal object before (vs. after) the hand/claw arrives there. Error bars represent standard-errors, and the asterisks mark predictive gaze with gaze-arrival times significantly above 0 ms, *** = p < .001.

Fig 3. Mean gaze-arrival times across trials 2–12 for the 6-, 11-, and 7-month-olds in the human hand action-effect condition and the no-action-effect condition of Experiments 1 and 2, and for the 7-month-olds in the claw-action-effect condition of Experiment 3.

Positive (vs. negative) values represent gaze arrival at the goal object before (vs. after) the hand/claw arrives there. Error bars represent standard-errors. The quadratic curve represents the regression function with most explained variance.