Selective Action Prediction in Infancy Depending on Linguistic Cues: An EEG and Eyetracker Study

Abstract

Humans' capacity to predict actions and to socially categorize individuals is at the basis of social cognition. Such capacities emerge in early infancy. By 6 months of age, infants predict others' reaching actions considering others' epistemic state. At a similar age, infants are biased to attend to and interact with more familiar individuals, considering adult-like social categories such as the language people speak. We report that these two core processes are interrelated early on in infancy. In a belief-based action prediction task, 6-month-old infants (males and females) presented with a native speaker generated online predictions about the agent's actions, as revealed by the activation of participants' sensorimotor areas before the agent's movement. However, infants who were presented with a foreign speaker did not recruit their motor system before the agent's action. The eyetracker analysis provided further evidence that linguistic group familiarity influences how infants predict others' actions, as only infants presented with a native speaker modified their attention to the stimuli as a function of the agent's forthcoming behavior. The current findings suggest that infants' emerging capacity to predict others' actions is modulated by social cues, such as others' linguistic group. A facilitation to predict and encode the actions of native speakers relative to foreign speakers may explain, in part, why infants preferentially attend to, imitate, and learn from the actions of native speakers.

Keywords: EEG; action prediction; eyetracker; infancy; social categorization; µ rhythm.

Figure 1.

Structure of the videos. A, First, infants saw the agent (A) reaching for a ball (O) when the ball jumped into a box (A+O+) and not moving when the ball jumped out of the box (A−O−). B, Second, the agent introduced herself in the participant's native language or in a foreign language. C, Third, the agent saw the ball jumping into (A+) or out of (A−) the box at the start of the video. Then a curtain came down hiding the agent, and the ball jumped either into (O+) or out of (O−) the box. When the curtain opened again, the agent remained still during 1,500 ms (anticipation period), and then she attempted to reach for the ball (A+O−; action trial) or remained still (A−O+; no-action trial) depending on her (false) belief about the ball's location. A successful prediction was associated with μ desynchronization prior to the agent's behavior (anticipation period) in the action trial (Experiment 1) and a different pattern of attention in the action versus no-action trials during the anticipation period, as measured by an eyetracker (Experiment 2). The WoA was defined as a window with onset at the “trigger” (when the curtain totally opened) and offset 500 ms later. Both trial types were randomly presented until infants became inattentive.

Figure 2.

ERSP in decibels relative to baseline. A, Spectrogram of the action trial separated by group (top, native group; bottom, foreign group), averaged across trials and channels (E30, E36, E37, and E42), and grand-averaged across participants in each group. The vertical line at Time 0 indicates the start of the WoA. The red rectangle defines the frequency (5–7 Hz) and time (0–500 ms) limits over which the analyses were computed (WoA). B, Topographic maps showing the average amplitude for all channels within the μ frequency range and 0–500 ms time window (WoA). The black circle delimits the four sensorimotor channels selected for the statistical analysis. C, Bars represent the averaged ERSP over the WoA with ±1 standard error, separated by trial type (x-axis) and group (color). A paired-sample t test found a significant difference between groups in the action trials; a one-sample t test found a significant decrease of μ only in the native group, but not in the other conditions (the symbol “*” indicates a p < 0.05). See Extended Data Figure 2-1 for details about the no-action trial.

Figure 3.

Results from a nonparametric test with 2,000 permutations (std_stat from EEGLAB) comparing ERSP depending on group and condition. A, The colored clusters indicate a significant (p < 0.05) interaction between the two factors. B, C, ERSP difference (in decibels) in the window of interest (0–500 ms) between the native group and the foreign group (native–foreign) in the no-action condition (B) and in the action condition (C). The green images depict the nonsignificance (p > 0.05) between the two groups (p < 0.05), and the colored clusters indicate a significant difference (p < 0.05). The color indicates the level of ERSP difference in decibels. As indicated in the color bar (bottom-right), the colder colors indicate a greater desynchronization in the native than the foreign group, and the warmer colors indicate the opposite.

Figure 4.

A, Time course (in seconds) of the t value describing the statistical difference in percentage of LT at the video (A1) and face (A2) between action relative to no-action trials for both language groups (blue, native group; salmon, foreign group). The horizontal dashed lines indicate the threshold from which p < 0.05 for each group. B, Time course of the mean percentage of LT at the video (B1) and face (B2) separated by group (color) and trial type (line type). The transparent rectangles indicate the clusters that were significant in a cluster mass test analysis with 2,000 permutations (blue, native group; orange, foreign group). The vertical dashed lines indicate the periods during the video when the curtain closed completely (Line 1, CClose), the curtain opened completely (beginning of the anticipation period; Line 2, Copen), and the agent acted in the action trials—but remained still in the no-action trials (end of the anticipation period; Line 3, Act?). See Extended Data Figures 4-1, 4-2, and 4-3 for more details about the AOIs, the average LT at each area, and the time course of infants’ LT at the box and the ball.