Abstract
Detection of a supra-threshold change has been reported to be very fast and accurate, and thus the comparison between memory and perceptual representations seems to occur very rapidly in an automatic fashion (Hyun et al., 2009). To explore further the nature of the comparison process, we used a visual masking paradigm in which complex pattern masks followed test items that are compared against remembered items in visual working memory. We also aimed to contrast the time course of this comparison process against the time course of visual working memory consolidation which is known to be relatively time consuming compared to simple feature pop-out detection (Vogel, Woodman, & Luck, 2006). In Experiment 1, subjects performed a color change detection task in which complex pattern masks followed either sample (sample-mask condition) or test items (test-mask condition) made of four-colored boxes, and the mask onset asynchrony (MSOA) in the sample-mask and test-mask conditions were varied to either 64 ms or 150 ms. Subjects' change detection performance was greatly impaired in the sample-mask condition for both 64 ms and 150 ms MSOA condition. However, in the test-mask condition, the performance for the 150 ms condition was much accurate compared to the performance for the 64 ms MSOA condition. In Experiment 2, we further manipulated display setsize from 1 to 4 and varied MSOA by 117, 234, 350, 584 ms. In the sample-mask condition, as the MSOA became shorter, increasing display setsize led to a stronger masking effect whereas the masking effect diminished in the test-masking condition. The results indicate that comparison between memory items and perceptual inputs is less vulnerable to interference from pattern-backward masking than VWM consolidation is, and support for the idea that detection of a visual change can be as efficient as detection of a pop-out feature in visual search.
This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (NRF-2010-0015349).