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Abstract
The present study focuses on two aspects of the time course of visual information processing during the perception of natural scenes. The first aspect is the change of fixation duration and saccade amplitude during the first couple of seconds of the inspection period, as has been described by Buswell (Citation1935), among others. This common effect suggests that the saccade amplitude and fixation duration are in some way controlled by the same mechanism. A simple exponential model containing two parameters can describe the phenomena quite satisfactorily. The parameters of the model show that saccade amplitude and fixation duration may be controlled by a common mechanism. The second aspect under scrutiny is the apparent lack of correlation between saccade amplitude and fixation duration (Viviani, Citation1990). The present study shows that a strong but nonlinear relationship between saccade amplitude and fixation duration does exist in picture viewing. A model, based on notions laid out by Findlay and Walker's (Citation1999) model of saccade generation and on the idea of two modes of visual processing (Trevarthen, Citation1968), was developed to explain this relationship. The model both fits the data quite accurately and can explain a number of related phenomena.
Notes
Please address all correspondence to: P. J. A. Unema, Faculty of Psychology, Maastricht University, PO Box 616, NL 6200 MD Maastricht, The Netherlands. Email: unema@applied‐cognition.org
The cooperation between the universities of Dresden and Maastricht was partially supported by a grant from the German Research Foundation (DFG), No. VE 192/8‐1. The authors thank Jens R. Helmert, Fiona Mulvey, Constanze Liebers, and Tilo Wehner for fruitful discussions and support in conducting this study. We also thank two anonymous reviewers for their helpful comments and suggestions.
Autoinhibition: a simple negative‐feedback loop; heteroinhibition: negative feedback provided by an independent unit.