Sustained visual attention in young infants measured with an adapted version of the visual preference paradigm

Phases of infant visual attention were studied using a visual preference procedure that was modified to be similar to a "dual-task," interrupted stimulus procedure. Infants were tested in a cross-sectional design at 14, 20, or 26 weeks of age. The infants were presented with varying and complex TV patterns on a TV monitor. At a delay from the onset of fixation on this stimulus, a similar pattern was presented on an adjacent TV monitor within the infant's field of vision. This secondary stimulus was presented either when heart rate (HR) decelerated significantly below prestimulus level or when the HR returned to prestimulus level. These 2 conditions correspond to sustained attention and attention termination phases of visual attention. The infants were less easily distracted by the secondary stimulus when HR was lower than prestimulus level than when it had returned to prestimulus levels. The amount of HR slowing on the HR deceleration trials increased over this age range, suggesting a developmental increase in sustained attention across this age range. The HR response at the time the infant looked at the secondary stimulus was different for the 2 delay conditions and differed from the HR response at primary stimulus onset. These results confirm the existence of distinct phases of attention during the visual preference procedure and suggest a refinement of the use of simple fixation time as a measure of infant attention with this procedure.