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Abstract:
Abstract: The ability to enumerate small number of objects
with high accuracy and speed (subitizing) has been attributed to a
special stage of visual processing (Trick & Pylyshyn, 1994). In
the present experiments, I wanted to understand the details of this
stage of visual processing. I varied the number of targets to be
enumerated, as well as the nature and the number of the distractors
present. In Experiment 1, subjects enumerated the number of red Os
among red Ls, blue Os and blue Ls. The number of red Ls present
varied from 0 to 4. The subitizing range for red Os shrank as the
number of red Ls increased. In Experiment 2, subjects enumerated
the number of red Os present among red Qs. Similar results were
observed. In Experiment 3, subjects enumerated the number of red Ls
present among mirror images of the red Ls (reverse Ls) and gray Os.
When no reverse-L distractors were present, subjects were able to
subitize. When only one reverse L was present, however, most
subjects gave up subitizing and switched to the laborious counting
process even when there were only 2 or 3 targets to be enumerated.
These results are discussed using theories developed from visual
search tasks.
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