Action Prediction Allows Hypothesis Testing via Internal Forward Models at 6 Months of Age

Abstract

We propose that action prediction provides a cornerstone in a learning process known as internal forward models. According to this suggestion infants' predictions (looking to the mouth of someone moving a spoon upward) will moments later be validated or proven false (spoon was in fact directed toward a bowl), information that is directly perceived as the distance between the predicted and actual goal. Using an individual difference approach we demonstrate that action prediction correlates with the tendency to react with surprise when social interactions are not acted out as expected (action evaluation). This association is demonstrated across tasks and in a large sample (n = 118) at 6 months of age. These results provide the first indication that infants might rely on internal forward models to structure their social world. Additional analysis, consistent with prior work and assumptions from embodied cognition, demonstrates that the latency of infants' action predictions correlate with the infant's own manual proficiency.

Keywords: action; eye tracking; interaction; internal model; prediction; pupil dilation.

FIGURE 1

Illustrations of the action prediction task (top, A), the action evaluation task (middle, B), and motor development task (bottom, C).

FIGURE 2

Correlations between key variables used to assess the presence of internal models in early infancy. All variables (Action prediction = latency in seconds, negative values = prediction; action evaluation = relative pupil dilation in mm positive values = surprise to inappropriate social interactions; motor performance = latency in seconds, negative values = prediction) maintain original format (variables are not flipped) as reported in prior work. Solid diagonal lines represent significant correlations (p < 0.05) whereas dashed line represent marginally significant interaction (p = 0.06). Horizontal and vertical lines mark zero-point (division between prediction and reaction for action prediction and motor development and between larger pupil to inappropriate or appropriate events for action evaluation).