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Marco J. H. Puts, Charles M. M. Weert; Temporal aspects of global form perception. Journal of Vision 2003;3(9):241. doi: 10.1167/3.9.241.
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Puts and de Weert (1998, Does colour influence subitization? Acta Psychologica, 97(1), 71–78) found that determining the number of presented elements was unaffected by color when the dots are in well-known, global configurations (e.g., three dots in triangular configuration, four dots in rectangular configuration and five dots in pentagonal configuration), while the counting is harder when all dots are placed in the same global configuration. They argue that determining the number can be done in two different ways. First of all by counting, secondly by using the shape information. The counting mechanism is not color blind, whereas the mechanism that is based on shape recognition is much faster and color blind. In the experiment to be reported here we investigated the temporal aspects of these two different mechanisms. In one condition, three, four or five dots were placed in well-known global configurations, called the form condition. In another condition, three, four or five dots were placed in a configuration where all dots were placed on a line, called the line condition. The patterns were alternated with a mask at different frequencies (7.5, 10, 15 and 30 Hz.), limiting the available time for detecting the target. Subjects had to perform a detection task, where they had to press a button when four dots were presented. We found out that in the form condition, the detectability showed a different behavior than in the line condition at different frequencies. There was no difference at 7.5 Hz. The difference in detectability was highest at 10 Hz. At this frequency, the configurations in the form condition were much more detectable than the configurations in the line condition, due to the highest contribution of the global form detection mechanism. At frequencies higher than 10 Hz., the difference in decreased with increasing frequency. On the basis of this experiment we may conclude that we have to do with two different ways of counting the dots.
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