Jason Clarke

Gist perception requires attention

Four experiments (240 subjects) explored gist perception without attention using the Mack and Rock (1998) cross task. Twelve scenes were flashed under conditions of inattention, divided, and full attention. Subjects described what they saw on critical trials in which a scene was flashed with the cross. In Experiments 3 and 4 subjects also chose the scene from a four scene array. In Experiment 4 the critical scenes were shown twice in the inattention condition. Overall, only 17% reported gist in the inattention condition, 65% did so with divided, and 82% did so with full attention. In Experiment 4 most subjects remained inattentionally blind to the scenes even though they were shown twice, conditions which fostered repetition priming, and we found a suggestion of negative priming. The results of all 4 experiments indicate that gist 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.

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 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.

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.

Iconic memory for natural scenes: Evidence using a modified change-detection procedure

ABSTRACT Change blindness for the contents of natural scenes suggests that only items that are attended while the scene is still visible are stored, leading some to characterize our visual experiences as sparse. Experiments on iconic memory for arrays of discrete symbols or objects, however, indicate observers have access to more visual information for at least several hundred milliseconds at offset of a display. In the experiment presented here, we demonstrate an iconic memory for complex natural or real-world scenes. Using a modified change detection task in which to-be changed objects are cued at offset of the scene, we show that more information from a natural scene is briefly stored than change blindness predicts and more than is contained in visual short-term memory. In our experiment, a cue appearing 0, 300, or 1000 msec after offset of the pre-change scene or at onset of the second scene presentation (a Post Cue) directed attention to the location of a possible change. Compared to a no-cue condition, subjects were significantly better at detecting changes and identifying what changed in the cue condition, with the cue having a diminishing effect as a function of time and no effect when its onset coincided with that of the second scene presentation. The results suggest that an iconic memory of a natural scene exists for at least 1000 msec after scene offset, from which subjects can access the identity of items in the pre-change scene. This implies that change blindness underestimates the amount of information available to the visual system from a brief glance of a natural scene.

Expectation Blindness: Seeing a face when there is none.

Taken together with our earlier reports, these findings are as convincing as behavioral data get, however they are not conclusive. The remaining question is whether, when observers report having seen the expected stimulus in its absence, they are actually hallucinating its presence (i.e. seeing it) or only inferring that the expected stimulus had been there. Current research in our lab is designed to try to answer this question. INTRODUCTION

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.

Inattentional blindness to absent stimuli: the role of expectation

While this is the rst report of inattentional blindness to the absence of an expected stimulus and so testi es to the perceptual nature of the phenomenon and against inattentional amnesia, more importantly our results highlight the powerful role expectation can play in perception. We do not know for certain that those Os who reported seeing a circle on the critical trials when there was none, actually hallucinated a yellow or blue circle. If they did, this may be the rst report in which unhypnotised or undrugged observers see something that is not there solely because they had built up an expectation to see it.

Evidence for iconic memory of natural scenes before change blindness

This study examined whether iconic memories for natural scenes, similar to those used in Rensink et al.s (1997) change blindness experiments, exist. A change detection procedure was used which included 120 scenes. Changes consisted of a deletion to the scene. Scenes were shown to each subject in one of four ways: change with cue (30 trials), change without cue (30 trials), no change with cue (30 trials), and no change without cue (30). There were two main conditions, each with twelve observers who were shown every scene (500 msec), followed by an inter-stimulus interval (1500 msec), and the same scene with or without a change (500 msec). In condition 1, on half of the trials, a red arrow (cue) appeared 0 msec after offset of the first scene, pointing to the location of a possible change. In condition 2, the cue appeared 300 msec after offset of the first scene. Observers reported change and the identity of the pre-change item. In both conditions, change detection and identification benefitted from the cue. In the first, the mean frequency of change detection with a cue (35%) was more than twice that without the cue (14%), and the mean frequency of change identification with a cue (29%) was almost three times that without a cue (10%). In the second, the mean change detection with a cue was 34% and 17% without it. Change identification with a cue (24%) was double that without it (11%). These results indicate that more information is available from a brief presentation of a natural scene than change blindness suggests, and that this information is available at least 300 msec after scene offset. Clearly the information in the iconic memory of scenes is sufficiently processed to afford some identification of the pre-change objects. Meeting abstract presented at VSS 2015.