Modeling spontaneous fixation durations in infancy: A simulation study with 6 month-olds

Fixation durations (FD) are well known to be indicators of attention and information processing, but how does control of FD develop during infancy? Can infants adapt their eye movements to different complex viewing conditions? In this study, eleven infants aged 6 months were presented with a set of customized naturalistic and non- naturalistic videos. They performed a gap-overlap task to measure inhibitory control, and a double-step task to investigate saccade cancelations. Results from this study revealed strong positive correlations between disengagement latencies and FD in the naturalistic and non-naturalistic conditions, as well as systematic changes across view- ing conditions. We propose a computational model (BabyCRISP, an adaptation of the CRISP model; Nuthmann et al, (2010). Psych. Rev.) that accounts for variabil- ity in FD in complex scenes based on mixed control theories of eye movements and the mechanisms underlying saccade programming. The comparison between the em- pirical data and the model simulations demonstrated how perceptual and cognitive activity can influence infant’s FDs and how variations in oculomotor control can be accounted for the parameters of this model. In the future, BabyCRISP will inform our understanding of the development of oculomotor control by enabling individual longitudinal developmental trajectories to be modelled.