Infant Eye-tracking in the Context of Goal-Directed Actions

Abstract

This paper presents two methods that we applied to our research to record infant gaze in the context of goal-oriented actions using different eye-tracking devices: head-mounted and remote eye-tracking. For each type of eye-tracking system, we discuss their advantages and disadvantages, we describe the particular experimental setups we used to study infant looking and reaching, explain how we were able to use and synchronize these systems with other sources of data collection (video recordings and motion capture) in order to analyze gaze and movements directed toward 3D objects within a common time frame. Finally, for each method, we briefly present some results from our studies to illustrate the different levels of analyses that may be carried out using these different types of eye-tracking devices. These examples aim to highlight some of the novel questions that may be addressed using eye-tracking in the context of goal-directed actions.

Figure 1

(a) Infant head-mounted eye-tracker used in our reaching study; (b) and (c) still frames of the video output provided by this eye-tracker on two different trials from the same infant, with the crosshair indicating where the infant is directing his gaze at this particular frame on the scene (Corbetta & Williams, 2011).

Figure 2

Illustration of synchronized times series from the eye-tracker (top graph) and motion tracker (3 bottom graphs: displacement, velocity, and rotation of the reaching arm). This example shows a trial in which the infants scanned the object horizontally prior to reaching.

Figure 3

Illustration of synchronized times series from the eye-tracker (top graph) and motion tracker (3 bottom graphs: displacement, velocity, and rotation of the reaching arm). This example shows a trial in which the infants did not scan the object horizontally prior to reaching.

Figure 4

Illustration of the setup used with the remote eye-tracker, (a) A computer screen is fitted in the board opening above the eye-tracker for calibration, (b) the computer screen has been removed and is replaced by two layers of black curtains for object presentation.

Figure 5

(a) Picture of a video camera fitted with the diode attached to and facing the lens used for synchronization; (b, c, d) Information seen on the coding station once all recording sources have been imported. (b) View from the eye-tracker scene camera with eye tracking data, (c) side views of the infant from the two reaching cameras, (d) time series from the motion tracker.

Figure 6

Example of gaze plots from a 9 months old infant illustrating where the child directed her visual attention on the object prior to reaching for it. In A, the infant reached to the top and in B, the infants reached to the right, the areas explored visually the most (from Corbetta et al., 2010).

Figure 7

Rate of matching between where the infant looked on the object prior to reaching and where she directed her arm for reaching. These data are from one infant followed longitudinally from week 16 (reach onset) to week 49.