Extended visual fixation in the early preschool years: look duration, heart rate changes, and attentional inertia.

Visual fixation in infants from 6 months to 2 years of age was examined for its fit to the theory of "attentional inertia." A children's movie ("Sesame Street" movie, "Follow that Bird") or an extended audiovisual stimulus (computer-generated patterns) was presented to 40 children for a minimum of 20 min while fixation was videotaped and heart rate (HR) was recorded. Consistent with attentional inertia theory, fixations toward the stimuli had a lognormal distribution, HR decreased over the course of a look, and HR returned to prestimulus levels immediately before look offset. Older children (18 months, 24 months) showed a distinction in the parameters describing the lognormal distribution for the "Sesame Street" movie and the audiovisual patterns, whereas younger children (6 months, 12 months) responded similarly to the two stimulus types. Fixation patterns of children in this age range suggest attention increases over the course of a look, and parameters consistent with attentional inertia theory differentially develop in this age range.