The full richness of the visual world becomes available to the infant at birth. Development of the visual system is very important, as the baby is hardly able to actively explore the environment in other ways. During the first five months of life, maturation of the cortical areas related to the control of eye movements and the processing of visual information leads to a major gain in the functionality of the visual system, in interaction with visual input from the environment [1]. For example, between four and eight weeks of age, infants cannot easily disengage their gaze from an interesting stimulus they have fixated: a phenomenon called 'sticky fixation'.

Visual attention, presumably controlled by posterior parietal areas in the brain, is essential to cognitive, motor and social development. Stable fixation of foveated objects and changes in the environment, and the selection of targets of interest in the peripheral world, are the main functions controlled by visual attention. The latter may lead to eye movement and the fixation of a new location. Thus, eye movements reflect attentional processes. Changes in heart rate and heart rate variability have been reported in both adults and infants in tasks requiring different levels of effort, and to stimuli that draw attention. These changes have generally been interpreted as an autonomic response to attention, and may serve as an independent marker of attention in the infant during visual attention tasks.

We studied the longitudinal development of visual attention and heart rate responses to visual stimuli in infants from six weeks to six months of age at four-week intervals. Infants were positioned in a semi-reclined position in a maxi cosy, 35 cm from a 21-inch monitor. Stimuli were presented in a central position and at 16 degrees to the left or right. Real time video records of the mother's smiling face and abstract dynamic video streams were used as stimuli. Eye movements were recorded on video and with an ASL eye tracker system (only 50% successful recordings). Heart rate and stimulus events were recorded separately. Data recording was synchronised between the systems. Video analysis (The Observer) of the frequency and latency of shifting gaze to a peripheral stimulus was performed at 20 ms resolution. These data were compared with the eye tracker data to enhance their accuracy.

Longitudinal data will be presented regarding the development of visual attention, involving both heart rate data and gaze shifts. Problems of measurement and integrated analysis of these varied data sources will be discussed.

References

1. Butcher, P.R.; Kalverboer, A.F.; Geuze, R.H. (2000). Infants' shift of gaze from a central to a peripheral stimulus: a longitudinal study of development between 6 and 26 weeks. Infant Behavior and Development, 23, 3-21.

Paper presented at Measuring Behavior 2002 , 4^th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands

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