How do eyes and brain search a randomly structured uninformative scene? Exploiting a basic interplay of attention and memory

We tracked the eye movements of seven young and seven older adults performing a conjunctive visual search task similar to that performed by two highly trained monkeys in an original influential study of Motter and Belky (1998a, 1998b). We obtained results consistent with theirs regarding elements of perception, selection, attention and object recognition, but we found a much greater role played by long-range memory. A design inadequacy in the original Motter-Belky study is not sufficient to explain such discrepancy, nor is the high level of training of their monkeys. Perhaps monkeys and humans do not use mnemonic resources compatibly already in basic visual search tasks, contrary to a common expectation, further supported by cortical representation studies. We also found age-related differences in various measures of eye movements, consistently indicating slightly reduced conspicuity areas for the older adults, hence, correspondingly reduced processing and memory capacities. However, because of sample size and age differential limitations, statistically significant differences were found only for a few variables, most notably overall reaction times. Results reported here provide the basis for demonstrating the formation of spiraling or circulating patterns in the eye movement trajectories and for developing corresponding computational models and simulations.

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