Abstract
Aim: Humans process a visual display more efficiently when they encounter it for a second time. When conducting visual search for a ‘T’ target presented among ‘L’ distracters, observers are faster at detecting the target when the same display is occasionally repeated, even when the repeated displays are not explicitly recognized. This study investigates how repeated presentation of natural scenes (rather than meaningless T-L configurations) affects visual search. In particular, we test the role of implicit learning and explicit associative memory in learning of natural scenes.
Method: Subjects searched for a ‘T’ among ‘L’s presented in a circular array against natural scenes or scrambled scenes. Each block contained 32 trials, divided randomly and evenly by two factors: background type (scene vs. scrambled image) and condition (repeated vs. nonrepeated). In repeated conditions, both the background image and the target location remain the same for each repetition. In the nonrepeated conditions, the background image was novel. We measured search RT throughout the experiment. At the end of the experiment, we tested explicit recognition of repeated scenes and recall of target locations for repeated scenes.
Results: In explicit recognition, subjects showed better scene recognition and displayed better target location memory for natural scenes over scrambled scenes. However, in visual search, RT advantage for repeated over nonrepeated displays was comparable between scenes and scrambled scenes. In addition, repeated scenes that were correctly recognized were not searched faster than repeated scenes that were missed in recognition. This suggests that while subjects have explicit memory for repeated natural scenes, visual search is facilitated primarily through implicit learning.
This research was funded by NIH MH071788 & ARO 46926-LS.