Negative Color Aftereffect in the Absence of a Colored Stimulus.

Negative color aftereffects normally occur following prolonged observation of colored surfaces and are generally attributed to sensory adaptation of opponent processes responsible for color vision. We describe evidence that negative color aftereffects, no different from those that occur when actually viewing red, are perceived in the complete absence of a colored stimulus by highly suggestible persons who are hypnotized and hallucinate seeing red. Highly suggestible participants also excel at imagining color although this is less likely to generate an aftereffect suggesting that there is more to hallucinating than imagining. Our results are clear evidence that sensory adaptation is not necessary for negative color aftereffects.

Effects of canonical color, luminance, and orientation on sustained inattentional blindness for scenes.

Whether scene gist perception occurs automatically and unconsciously has been the subject of much debate. In addition to demonstrating a new method that adapts the Mack and Rock (1998) inattentional blindness cross procedure to allow for sustained inattentional blindness over a large number of trials, we report evidence from a series of experiments that shows that canonical scene features reduce inattentional blindness to scenes by facilitating the extraction of scene gist. When attentional demands are high, the combination of canonical color, canonical luminance, and canonical orientation reduces rates of inattentional blindness. However, when attentional demands are reduced, canonical features are independently sufficient to facilitate gist extraction and to capture attention. These results demonstrate that canonical color, canonical luminance, and canonical orientation all contribute to scene gist perception, and that when attentional demands are high, only highly canonical stimuli are sufficient to capture attention.

Scene incongruity and attention.

Does scene incongruity, (a mismatch between scene gist and a semantically incongruent object), capture attention and lead to conscious perception? We explored this question using 4 different procedures: Inattention (Experiment 1), Scene description (Experiment 2), Change detection (Experiment 3), and Iconic Memory (Experiment 4). We found no differences between scene incongruity and scene congruity in Experiments 1, 2, and 4, although in Experiment 3 change detection was faster for scenes containing an incongruent object. We offer an explanation for why the change detection results differ from the results of the other three experiments. In all four experiments, participants invariably failed to report the incongruity and routinely mis-described it by normalizing the incongruent object. None of the results supports the claim that semantic incongruity within a scene invariably captures attention and provide strong evidence of the dominant role of scene gist in determining what is perceived.

No iconic memory without attention.

The experiments reported extend the findings of our earlier paper, (Mack, Erol, & Clarke, 2015) and allow us to reject Bachmann and Aru's critique of our conclusion (2015) that IM requires attention. They suggested our manipulations, which diverted attention from a letter reporting task in a dual task procedure where the task-cue occurred after the array disappeared, might only have affected access to IM and not the "existence of the phenomenal experience". By further decreasing the probability of reporting letters to only 10% and adding a final trial in which the letter matrix was either completely absent or distorted, we found more than half our subjects were unaware of its absence, or distortion i.e., were inattentionally blind. We take this as powerful evidence against the existence of any phenomenal experience component of iconic memory and consistent with the view that iconic memory demands attention and that conscious perception does as well.

Reply to Bachmann and Aru.

A reply to the Bachmann and Aru (2015) critique of our paper (Mack, Erol, & Clarke, 2015) in which we rebut their criticisms and argue once again that our results support our view that iconic memory requires attention.

Iconic memory is not a case of attention-free awareness.

Whether or not awareness entails attention is a much debated question. Since iconic memory has been generally assumed to be attention-free, it has been considered an important piece of evidence that it does not (Koch & Tsuchiya, 2007). Therefore the question of the role of attention in iconic memory matters. Recent evidence (Persuh, Genzer, & Melara, 2012), suggests that iconic memory does depend on attention. Because of the centrality of iconic memory to this debate, we looked again at the role of attention in iconic memory using a standard whole versus partial report task of letters in a 3×2 matrix. We manipulated attention to the array by coupling it with a second task that was either easy or hard and by manipulating the probability of which task was to be performed on any given trial. When attention was maximally diverted from the matrix, participants were able to report less than a single item, confirming the prior results and supporting the conclusion that iconic memory entails attention. It is not an instance of attention-free awareness.

Iconic memory for the gist of natural scenes.

Does iconic memory contain the gist of multiple scenes? Three experiments were conducted. In the first, four scenes from different basic-level categories were briefly presented in one of two conditions: a cue or a no-cue condition. The cue condition was designed to provide an index of the contents of iconic memory of the display. Subjects were more sensitive to scene gist in the cue condition than in the no-cue condition. In the second, the scenes came from the same basic-level category. We found no difference in sensitivity between the two conditions. In the third, six scenes from different basic level categories were presented in the visual periphery. Subjects were more sensitive to scene gist in the cue condition. These results suggest that scene gist is contained in iconic memory even in the visual periphery; however, iconic representations are not sufficiently detailed to distinguish between scenes coming from the same category.

Change blindness and priming: When it does and does not occur.

In a series of three experiments, we explored the nature of implicit representations in change blindness (CB). Using 3 x 3 letter arrays, we asked subjects (Ss) to locate changes in paired arrays separated by 80 ms ISIs, in which one, two or three letters of a row in the second array changed. In one testing version, a tone followed the second array, signaling a row for partial report (PR). In the other version, no PR was required. After Ss reported whether a change had been detected and the PR had been completed (if required), they were asked to identify a degraded letter trigram that was either novel, or from a previously shown row (repetition priming). Our findings indicate that when CB occurs, both the pre-change and post-change stimulus information primes despite its unavailability to consciousness. Surprisingly, findings also indicate that when change detection occurs only the post-change information primes.

What we see: inattention and the capture of attention by meaning.

Attention is necessary for the conscious perception of any object. Objects not attended to are not seen. What is it that captures attention when we are engaged in some attention-absorbing task? Earlier research has shown that there are only a very few stimuli which have this power and therefore are reliably detected under these conditions (for example, Mack & Rock, 1998; Moray, 1959). The two most reliable are the observer's own name and a happy face icon which seem to capture attention by virtue of their meaning. Three experiments are described which explore whether these stimuli are detected under conditions, heretofore unexamined, which either cause inattentional blindness or are associated with a perceptual failure associated with the limits of attention. The evidence obtained indicates that these stimuli have a unique capacity to capture and extend the limits of attention under conditions in which this has been deemed highly unlikely.