Encoding features of complex and unfamiliar objects.

This study explored the acquisition of features from complex, unfamiliar objects. It tested the principle of top-down encoding, which predicts that the time needed to detect a difference between stimuli that differ in only one critical feature increases and recognition decreases as the level of that feature decreases. Results of Experiment 1 supported these hypotheses. Experiment 2 eliminated retroactive interference as an explanation for the results of Experiment 1. Experiment 3 showed that top-down encoding can be altered by explicit instructions to attend the relevant feature. It also showed that discriminability due to size was not a factor in Experiments 1-3. Experiment 4 showed that the top-down principle can account for how people encode features as a function of task demands. Overall, the results indicate that under normal attention conditions, the probability of encoding a feature decreases with its structural level. However, this tendency can be altered by explicit instructions or other factors.