Yet, the repetition of briefly presented pictures improves memory performance. Therefore, long enough stimulus duration seems necessary to encode and recall complex visual scenes in details. Generally, the amount of details remembered about a stimulus increases linearly with more time to encode them ( Brady et al., 2009). Other studies argued that scene representations would first be represented as a general layout or gist and details about specific objects would be added on subsequent fixations ( Melcher, 2001 Melcher and Kowler, 2001 Tatler et al., 2003). For example, Potter (1976) showed that it is possible to remember 80% of masked pictures when presented for 120 ms but only 50% if presented for only 50 ms. However, it is well known that recognition memory suffers when stimulus duration decreases ( Shaffer and Shiffrin, 1972 Potter, 2012). In these studies, presentation time of the stimuli was very long (from 3 to 20 s). These results demonstrate that humans have a massive and detailed memory capacity for pictures. Impressively, participants successfully discriminated between the previously seen object and the new one with 87% accuracy in the state condition. The new picture could either be an object from a different category, a new exemplar from the same category, or the same object but in a different state. (2008), after viewing 2500 pictures of objects, participants were shown two images and asked which of the two they had seen in a two-alternative forced choice (2AFC). For example, in the study of Brady et al. More impressively, recent studies have showed that the representations stored in memory are precise ( Hollingworth and Henderson, 2002 Vogt and Magnussen, 2007 Brady et al., 2008). Humans can remember thousands of pictures after a single exposure of 5 s ( Shepard, 1967 Standing et al., 1970, Standing, 1973). These results show that briefly flashed unmasked scenes can be incidentally stored in long-term memory when repeated. As early as 230 ms after stimulus onset, a significant event-related-potential (ERP) difference between familiar and new images was observed for the trained but not for the untrained group. EEG recordings confirmed these behavioral results. On the other hand, trained participants, who had processed the flashed images (20 ms) several times, could correctly recognize 89% of them. Compared to previous reports of excellent recognition performance with only single presentations of a few seconds, untrained participants were able to recognize only 64% of the 200 images they had seen few minutes before. 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). In this experiment, we tested recognition performance for natural scenes that participants saw for 20 ms only once (untrained group) or 22 times over many days (trained group) in an unrelated task. 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. The capacity of human memory is impressive. 4Institute of Noetic Sciences, Petaluma, CA, United States.3Institute for Neural Computation, University of California, San Diego, La Jolla, CA, United States.2Centre National de la Recherche Scientifique, Centre de Recherche Cerveau et Cognition, Toulouse, France.1Centre de Recherche Cerveau et Cognition, Université Toulouse III - Paul Sabatier, Toulouse, France.Arnaud Delorme 1,2,3,4*, Marlène Poncet 1,2 and Michèle Fabre-Thorpe 1,2
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