Influence of Selection Difficulty on the Time Required for Icon Formation

By increasing the number of display items and the physical similarity between the target and the irrelevant items it was possible to vary the difficulty of target selection in a visual-search task. The results showed that the accuracy with which the target was located declined as target selection became more difficult. On the other hand, estimates of the cumulative probability and the probability distributions of times necessary to form the icon indicated that these times were not influenced by changes in the difficulty of the task. The latter result supports Neisser's suggestion that the information processing carried out during the first stage of analysis can be attributed to the action of a distinct cognitive mechanism.