Fig 1.
The MET contains a scene camera and an eye camera. The scene camera points straight ahead to record the infant’s approximate head-centered field of view. The eye camera points in to the infant’s eye to record eye movements.
Fig 2.
Schematic drawings of infants’ field of view (FOV) in sitting and prone positions.
An infant (A) sitting or (B) prone on the ground with a close toy (blue oval) and a far toy (orange oval). The rectangles on the right of the figure depict infants’ approximate first-person FOV in sitting and prone positions (not drawn to scale). (A) In the sitting infant’s FOV, close toys are in relatively lower locations, whereas far toys are in relatively higher locations. (B) In the prone infant’s FOV, close toys appear large, whereas far toys are out of view.
Fig 3.
Coders used the Matlab program Dynamic ROI Coder to draw a box around the toy in each frame of infants’ field of view video.
Fig 4.
Looking episode and centering.
A frame was defined as a looking episode when eye gaze (green cross) fell on or within ROI (yellow ellipse). Centering (red line) was the distance of toy location to the center of the field of view (white dot).
Fig 5.
Coders went through third-person view videos to score toy distance. Toys within the reference distance (yellow line) were coded as close to the infant, whereas toys beyond the reference distance were coded as far.
Fig 6.
Centering and spread by posture, toy looking, and toy distance.
(A) Centering and (B) spread of close toys (blue symbols) and far toys (orange symbols) during looking and non-looking episodes across postures. For centering, smaller values on the y-axis indicate better centering. For spread, smaller values on the y-axis indicate less variability of toy locations in the field of view.
Table 1.
Descriptive statistics (M and SD in pixels) for centering by posture, looking, and toy distance.
Table 2.
Summary of LMM results predicting centering from posture, looking, and toy distance.
Degrees of freedom and resulting p values obtained using the Satterthwaite approximation.
Table 3.
Descriptive statistics (M and SD in pixels) for spread by posture, looking, and toy distance.
Table 4.
Summary of LMM results predicting spread from posture, looking, and toy distance.
Degrees of freedom and resulting p values obtained using the Satterthwaite approximation.