Peripheral stimulus localization by infants with eye and head movements during visual attention.

The effect of attention to a focal stimulus on 14, 20 and 26-week-old infant's peripheral stimulus localization with eye and head movements was examined in this study. Fixation was engaged on a stimulus in the central visual field and a stimulus was presented in the periphery immediately or after a delay. Peripheral stimulus localization occurred less frequently near the beginning of fixation and when a significant heart rate deceleration had occurred (sustained attention), compared with when no focal stimulus was present or after heart rate had returned to prestimulus level (attention termination). Localization was accompanied by head movements on more than two-thirds of the trials, and the likelihood of head movements was positively associated with stimulus eccentricity. The saccades to localize the peripheral stimulus had unusually high velocities in the attention conditions for the two older aged groups relative to their saccades in inattentive conditions. There were unusual "localizing head movements" in the attention conditions in the absence of localizing saccades or changes in fixation for the two older age groups. Infant attention modulates eye movement characteristics of infants. These data also support the hypothesis that eye and head movement systems are relatively independent in the infant, and that eye-head relations during infant attention may be different from during inattention.