The role of expectancy in perceiving the environment : an experimental lab study.

This report deals with Automatic Visual Information Processing (AVIP), indicating a state, in which expectations have replaced a large part of the active information intake compared to a highly attentive person. The purpose of the conducted experiments was to test two hypotheses: 1) if people have expectations about what information is relevant and what information is not, more time will be spent looking at information that is expected to be relevant; 2) if information is presented that does not correspond with the expectations, the information will either be missed or response will be low. A laboratory task was developed, simulating a moving environment with a continuous stream of stimuli approaching the subject. Subjects had to decide whether a stimulus was a target or a distractor. If it was a target, subjects had to respond by pressing a mouse button. Eye movements were measured. In one condition, the sequence of targets and distractors was predictable, in the other condition, the sequence was random. The predictable condition allowed subjects to develop expectations. Every now and then, a stimulus that was expected to be a distractor in the predictable condition was a target. The combined results of the experiments showed that subjects with expectations scan their environment differently than subjects without expectations about what stimuli will be targets and what will be the distractors. In case of expectancy, less time is spent fixating the distractors. For those subjects that do not have expectations about the stimuli, the same amount of time is spent to targets and distractors and responses to targets are slower. However, is some information is included that is not in congruence with the expectations people have, this information is either missed or the responses to the appearance of the targets are slow, with responses even being slower than in the random condition. After encountering several of these irregularities, a change in scanning pattern is found, with subjects adjusting their scanning strategy more towards the scanning pattern of the random condition. These results show that the hypothesis were correct. (A)