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Journal of Ophthalmology
Volume 2014 (2014), Article ID 237812, 14 pages
Research Article

Centre-of-Gravity Fixations in Visual Search: When Looking at Nothing Helps to Find Something

1The University of Queensland, Brisbane, Australia
2School of Psychology, The University of Queensland, McElwain Building, Brisbane, QLD 4072, Australia
3Centre for Interdisciplinary Research, Bielefeld University, 33602 Bielefeld, Germany
4The University of Bielefeld, Bielefeld, Germany

Received 8 December 2013; Revised 12 February 2014; Accepted 28 February 2014; Published 3 June 2014

Academic Editor: Arvid Herwig

Copyright © 2014 Dustin Venini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In visual search, some fixations are made between stimuli on empty regions, commonly referred to as “centre-of-gravity” fixations (henceforth: COG fixations). Previous studies have shown that observers with task expertise show more COG fixations than novices. This led to the view that COG fixations reflect simultaneous encoding of multiple stimuli, allowing more efficient processing of task-related items. The present study tested whether COG fixations also aid performance in visual search tasks with unfamiliar and abstract stimuli. Moreover, to provide evidence for the multiple-item processing view, we analysed the effects of COG fixations on the number and dwell times of stimulus fixations. The results showed that (1) search efficiency increased with increasing COG fixations even in search for unfamiliar stimuli and in the absence of special higher-order skills, (2) COG fixations reliably reduced the number of stimulus fixations and their dwell times, indicating processing of multiple distractors, and (3) the proportion of COG fixations was dynamically adapted to potential information gain of COG locations. A second experiment showed that COG fixations are diminished when stimulus positions unpredictably vary across trials. Together, the results support the multiple-item processing view, which has important implications for current theories of visual search.