To allow the separation of the signal evoked by each event, a blank screen (medium gray) was presented as an interstimulus interval (ISI) for a period of 2, 3, or 4 s (picked randomly) between the CAM1, SOL, and CAM2 stages. A randomly picked intertrial interval (ITI) of 3, 4, or 5 s was also used. For determination of memory performance

in the Test session (Figure 3B), all 40 camouflage images from the stimulus set were presented to each participant. Thirty images (and their solutions) Bioactive Compound Library were therefore previously seen (in the Study session), and the remaining ten images were novel (different ones for different participants). Each camouflage image was presented for 10 s, and the participants were instructed to press a

button if they thought they identified the object in the image. Once they pressed the button, or after 10 s if they did not press it, the four-option multiple choice question appeared, and the participants were requested to identify the object in the image by pressing one of four numbers on a keypad. The question remained on the screen until a response was given, but not for longer than 10 s, and the next camouflage image was then presented. If a choice was made within the 10 s limit, participants were next asked to indicate their level of confidence: BKM120 “guess,” “fairly confident,” or “completely confident.” Regardless of the confidence level indicated, if their answer to the multiple choice question was correct, the camouflage image was Urease re-presented, with a Grid-map of numerals (1–9) superimposed on it (Grid task). Participants were asked to specify the Grid-map numeral overlaid on a specific feature of the object

(e.g., “the eye of the clown,” Figure 3B). The object features queried at the Grid questions were ones that are not likely to be distinctive by themselves, but rather those whose identification was facilitated by a holistic perception of the embedded object. The image with the Grid-map was presented until a response was provided, but not for more than 10 s. The chance level, combining the multiple choice question and the Grid task question, is only 2.75% (25% at the multiple choice question followed by 11% at the grid-map question). Therefore, in all subsequent analyses correct responses on both tests were used as indication that the observer perceived the underlying scene correctly. This classification was supported by two analyses. First, we compared the number of these images with the expected number of chance correct answers in the multiple choice task. The expected number of chance correct answers (computed individually for each participant) is the number of images that were indicated as not identified in the Study whose perceptual identification was not verified in the Grid task, divided by four. The comparison of those two sets of numbers revealed that they did not differ significantly (p = 0.15).