Abstract
The capacity of human memory is very impressive. Previous reports have shown that when asked to memorize images, participants can recognize several thousands of visual objects in great details even with a single viewing of a few seconds per image. In this experiment, we tested recognition performance for natural scenes that participants saw for only 20ms in an unrelated task. A group of participants performed an animal/non-animal categorization task for 15 days on the same 200 images. One week later, this trained group and another untrained group of participants saw the 200 images once (for the first time for the untrained group) and were tested 10 minutes later in an unexpected recognition task along with EEG recordings. In this task, 400 images (200 previously viewed and 200 novel images) were flashed one at a time and participants were asked to lift their finger from a pad whenever they thought they had already seen the image (go/no-go paradigm). Compared to previous reports of excellent recognition performance with only single presentations of a few seconds, untrained participants were able to recognize only 59% of the 200 images they had seen few minutes before. On the other hand, trained participants, who had seen the images 21 times (20ms each), could correctly recognize 87% of them. EEG recordings confirmed these behavioral results. As early as 230ms after stimulus onset, a significant ERP difference between familiar and new images was observed for the trained but not for the untrained group. Consistent with previous literature, for both the trained and the untrained group, we also found an automatic processing of visual object categories, demonstrated by an ERP difference between animal and non-animal images around 170ms after stimulus onset. These results show that briefly flashed unmasked scenes can be incidentally stored in long-term memory when repeated.
Meeting abstract presented at VSS 2014