Repetition blindness and illusory conjunctions: errors in binding visual types with visual tokens.

Repetition blindness (Kanwisher, 1986, 1987) has been defined as the failure to detect or recall repetitions of words presented in rapid serial visual presentation (RSVP). The experiments presented here suggest that repetition blindness (RB) is a more general visual phenomenon, and examine its relationship to feature integration theory (Treisman & Gelade, 1980). Experiment 1 shows RB for letters distributed through space, time, or both. Experiment 2 demonstrates RB for repeated colors in RSVP lists. In Experiments 3 and 4, RB was found for repeated letters and colors in spatial arrays. Experiment 5 provides evidence that the mental representations of discrete objects (called "visual tokens" here) that are necessary to detect visual repetitions (Kanwisher, 1987) are the same as the "object files" (Kahneman & Treisman, 1984) in which visual features are conjoined. In Experiment 6, repetition blindness for the second occurrence of a repeated letter resulted only when the first occurrence was attended to. The overall results suggest that a general dissociation between types and tokens in visual information processing can account for both repetition blindness and illusory conjunctions.     

Curved apparent motion induced by amodal completion

We investigated whether amodal completion can bias apparent motion (AM) to deviate from its default straight path toward a longer curved path, which would violate the well-established principle that AM follows the shortest possible path. Observers viewed motion sequences of two alternating rectangular tokens positioned at the ends of a semicircular occluder, with varying interstimulus intervals (ISIs; 100-500?ms). At short ISIs, observers tended to report simple straight-path motion-that is, outside the occluder. But at long ISIs, they became increasingly likely to report a curved-path motion behind the occluder. This tendency toward reporting curved-path motion was influenced by the shape of tokens, display orientation, the gap between tokens and the occluder, and binocular depth cues. Our results suggest that the visual system tends to minimize unexplained absence of a moving object, as well as its path length, such that AM deviates from the shortest path when amodal integration of motion trajectory behind the curved occluder can account for the objective invisibility of the object during the ISI.     

Orientation-invariant object recognition: evidence from repetition blindness

The question of whether object recognition is orientation-invariant or orientation-dependent was investigated using a repetition blindness (RB) paradigm. In RB, the second occurrence of a repeated stimulus is less likely to be reported, compared to the occurrence of a different stimulus, if it occurs within a short time of the first presentation. This failure is usually interpreted as a difficulty in assigning two separate episodic tokens to the same visual type. Thus, RB can provide useful information about which representations are treated as the same by the visual system. Two experiments tested whether RB occurs for repeated objects that were either in identical orientations, or differed by 30, 60, 90, or 180 degrees . Significant RB was found for all orientation differences, consistent with the existence of orientation-invariant object representations. However, under some circumstances, RB was reduced or even eliminated when the repeated object was rotated by 180 degrees , suggesting easier individuation of the repeated objects in this case. A third experiment confirmed that the upside-down orientation is processed more easily than other rotated orientations. The results indicate that, although object identity can be determined independently of orientation, orientation plays an important role in establishing distinct episodic representations of a repeated object, thus enabling one to report them as separate events.     

Looking at object-substitution masking in depth and motion: toward a two-object theory of object substitution

When attention is divided, a briefly presented target surrounded by four small dots is difficult to identify when the dots persist beyond target offset, but not when these dots terminate with the target. This object-substitution masking effect likely reflects processes at both the image level and the object level. At the image level, visual contours of the mask make feature extraction difficult. Recent data (Lleras & Moore, 2003) suggest that, at the object level, an object file is created for the target-plus-mask, and this single-object token later morphs into a single-object token containing the mask alone. In the present experiments, we used stimuli presented in 3-D space and apparent motion; the results indicate that object-substitution masking also arises when the mask and the target are represented in two separate object tokens and the mask token interferes with the target token.     

Perception of successive targets presented in invariant-item streams

When two successive, spatially overlapping, targets (S1 and S2) are presented on a blank background, S2 typically dominates in explicit perception. We tested whether S2 dominance is also found for the conditions of presenting S1 and S2 in a stream of irrelevant objects. Successive target letters were presented within a stream of invariant stimulus items (capital Is). The stream items were presented either as a perceptually continuous object where both type and token appeared invariant (60-Hz stream) or as a flickering stream of successive replicas of the invariant stationary object where the type appeared invariant but the token appearance seemed intermittent (20-Hz condition). Compared to the control condition where targets were presented on a blank background we found that (1) recognition rate was lower for targets embedded in a perceptually continuous type-and-token object (60 Hz), but was unchanged for targets in a perceptually flickering sequence of the invariant-object tokens (20 Hz); (2) S1 recognition rate was higher compared to S2 recognition rate within the first epoch of stream (0-150 ms) while within the later stream-epochs S2 dominated over S1 as usual; (3) the overall difference in recognition rates between S1 and S2 was decreased. The results are discussed in the theoretical context of visual masking and attentional blink.     

Repetition blindness: The survival of the grouped

The repetition blindness (RB) effect demonstrates that people often fail to detect the second presentation of an identical object (e.g., Kanwisher, 1987). Grouping of identical items is a well-documented perceptual phenomenon, and this grouping generally facilitates perception. These two effects pose a puzzle: RB impairs perception, while perceptual grouping improves it. Here, we combined these two effects and studied how they interact. In a series of three experiments, we presented repeated items in a simultaneous string, while manipulating the organization of the repeated items in groups within a string. We observed an interaction between RB and grouping that we summarize with a rule that we call “the survival of the grouped”: In essence, the ability to group repeated elements protects them from RB. These findings are discussed within the framework of the object file theory.     

Two scenes or not two scenes: The effects of stimulus repetition and view-similarity on scene categorization from brief displays

Previous research suggests that understanding the gist of a scene relies on global structural cues that enable rapid scene categorization. This study used a repetition blindness (RB) paradigm to interrogate the nature of the scene representations used in such rapid categorization. When stimuli are repeated in a rapid serial visual presentation (RSVP) sequence (~10 items/sec), the second occurrence of the repeated item frequently goes unnoticed, a phenomenon that is attributed to a failure to consolidate two conscious episodes (tokens) for a repeatedly activated type. We tested whether RB occurs for different exemplars of the same scene category, which share conceptual and broad structural properties, as well as for identical and mirror-reflected repetitions of the same scene, which additionally share the same local visual details. Across 2 experiments, identical and mirror-image scenes consistently produced a repetition facilitation, rather than RB. There was no convincing evidence of either RB or repetition facilitation for different members of a scene category. These findings indicate that in the first 100–150 ms of processing scenes are represented in terms of local visual features, rather than more abstract category-general features, and that, unlike other kinds of stimuli (words or objects), scenes are not susceptible to token individuation failure.     

Amodal representation of occluded surfaces: role of invisible stimuli in apparent motion correspondence

A series of demonstrations were created where the perceived depth of targets was controlled by stereoscopic disparity. A closer object (a cloud) was made to jump back and forth horizontally, partially occluding a farther object (a full moon). The more distant moon appeared stationary even though the unoccluded portion of it, a crescent, changed position. Reversal of the relative depth of the moon and cloud gave a totally different percept: the crescent appeared to flip back and forth in the front depth plane. Thus, the otherwise-robust apparent motion of the moon crescents was completely abolished in the cloud-closer case alone. This motion-blocking effect is attributed to the 'amodal presence' of the occluded surface continuing behind the occluding surface. To measure the effect of this occluded 'invisible' surface quantitatively, a bistable apparent motion display was used (Ramachandran and Anstis 1983a): two small rectangular-shaped targets changed their positions back and forth between two frames, and the disparity of a large centrally positioned rectangle was varied. When the perceived depths supported the possibility of amodal completion behind the large rectangle, increased vertical motion of the targets was found, suggesting that the amodal presence of the targets behind the occluder had effectively changed the center position of the moving targets for purposes of motion correspondence. Amodal contours are literally 'invisible', yet it is hypothesized that they have a neural representation at sufficiently early stages of visual processing to alter the correspondence solving process for apparent motion.     

Visual events modulated by sound in repetition blindness

Repetition blindness (RB; Kanwisher, 1987) is the term used to describe people’s failure to detect or report an item that is repeated in a rapid serial visual presentation (RSVP) stream. Although RB is, by definition, a visual deficit, whether it is affected by an auditory signal remains unknown. In the present study, we added two sounds before, simultaneous with, or after the onset of the two critical visual items during RSVP to examine the effect of sound on RB. The results show that the addition of the sounds effectively reduced RB when they appeared at, or around, the critical items. These results indicate that it is easier to perceive an event containing multisensory information than unisensory ones. Possible mechanisms of how visual and auditory information interact are discussed.     

Neural correlates of transformational apparent motion

Transformational apparent motion (TAM) arises when a shape that is abruptly flashed on and off next to a static shape of similar color or texture appears as a protrusion that extends and retracts smoothly from the static object. Here we report that the strength of the TAM percept can be predicted from the waveform of visual evoked potentials (VEPs) measured while observers rated their percepts. The VEPs at pattern onset and offset are maximally symmetric when the static inducer and the flashing patches of the display are of the same contrast. VEP symmetry is affected by how the two patches can be matched as a single surface and may reflect the relative contribution of different motion and object detection systems in visual cortex.     

Visual and phonological codes in repetition blindness.

Repetition blindness (RB) is the inability to detect or recall a repeated word in rapid serial visual presentation. The role of visual versus phonological (name) similarity in RB was examined. RB was found for single letters, whether printed in the same or different cases, and for single digits, whether represented verbally (nine), as arabic numerals (9), or in a mixture of the 2 formats. Hence, visual similarity is not necessary to produce RB. RB was obtained between homophonic pairs (won/one), showing that phonological similarity is sufficient to produce RB, although visual identity also contributes to RB. It is proposed that RB results when the codes used for initial registration of the targets in short-term memory are similar. This initial code may be predominantly visual or predominantly phonological.     

Modality-specific auditory and visual temporal processing deficits

We studied the attentional blink (AB) and the repetition blindness (RB) effects using an audio-visual presentation procedure designed to overcome several potential methodological confounds in previous cross-modal research. In Experiment 1, two target digits were embedded amongst letter distractors in two concurrent streams (one visual and the other auditory) presented from the same spatial location. Targets appeared in either modality unpredictably at different temporal lags, and the participants' task was to recall the digits at the end of the trial. We evaluated both AB and RB for pairs of targets presented in either the same or different modalities. Under these conditions both AB and RB were observed in vision, AB but not RB was observed in audition, and there was no evidence of AB or RB cross-modally from audition to vision or vice versa. In Experiment 2, we further investigated the AB by including Lag 1 items and observed Lag 1 sparing, thus ruling out the possibility that the observed effects were due to perceptual and/or conceptual masking. Our results support a distinction between a modality-specific interference at the attentional selection stage and a modality-independent interference at later processing stages. They also provide a new dissociation between the AB and RB.     

Repetition blindness has a perceptual locus: evidence from online processing of targets in RSVP streams

Four experiments tested whether repetition blindness (RB; reduced accuracy reporting repetitions of briefly displayed items) is a perceptual or a memory-recall phenomenon. RB was measured in rapid serial visual presentation (RSVP) streams, with the task altered to reduce memory demands. In Experiment 1 only the number of targets (1 vs. 2) was reported, eliminating the need to remember target identities. Experiment 2 segregated repeated and nonrepeated targets into separate blocks to reduce bias against repeated targets. Experiments 3 and 4 required immediate "online" buttonpress responses to targets as they occurred. All 4 experiments showed very strong RB. Furthermore, the online response data showed clearly that the 2nd of the repeated targets is the one missed. The present results show that in the RSVP paradigm, RB occurs online during initial stimulus encoding and decision making. The authors argue that RB is indeed a perceptual phenomenon.     

Is target movement as well as target displacement a stimulus for saccadic eye movements?

The effects of visual movement on saccadic eye movement have been examined. In a classic apparent-movement demonstration with two successively exposed line-segment targets the quality of the movement is dependent on the relative orientation of the line segments. If saccadic eye movements are elicited between the targets in this situation, the configuration leading to optimal apparent movement also leads to the shortest-latency saccades. When a single line segment is succeeded by two line segments flanking it on opposite sides, and if one of these has the same orientation as the initial one and the other a different orientation, then apparent motion is seen between the two lines with the same orientation. However, the direction of saccades elicited in this configuration is not influenced by the relative orientations of the line segments. The two results together suggest that the effect of visual movement on saccadic eye movement is nonspecific.     

Motion, not masking, provides the medium for feature attribution

ABSTRACT— Understanding the dynamics of how separate features combine to form holistic object representations is a central problem in visual cognition. Feature attribution (also known as feature transposition and feature inheritance) refers to the later of two stimuli expressing the features belonging to the earlier one. Both visual masking and apparent motion are implicated in feature attribution. We found that when apparent motion occurs without masking, it correlates positively with feature attribution. Moreover, when apparent motion occurs with masking, feature attribution remains positively correlated with apparent motion after the contribution of masking is factored out, but does not correlate with masking after the contribution of apparent motion is similarly factored out. Hence, motion processes on their own provide the effective medium for feature attribution. Our results clarify the dynamics of feature binding in the formation of integral and unitary object representations in human vision.     

Object substitution masking and the object updating hypothesis

The object updating hypothesis of object substitution masking proposes that the phenomenon arises when the visual system fails to individuate target and mask at the level of object token representations. This hypothesis is tested in two experiments using modifications of the dot mask paradigm developed by Lleras and Moore (2003). Target—mask individuation is manipulated by the presentation of additional display items that influence the linking apparent motion seen between a target and a spatially separated mask (Experiment 1), and by the use of placeholders that maintain the target object’s presence during mask presentation (Experiment 2). Results in both cases are consistent with the updating hypothesis in showing significantly reduced masking when the conditions promoted target—mask individuation. However, in both experiments, some masking was still present under conditions of individuation, an effect we attribute to attentional capture by the mask.     

飞行员动态空间表征建构的策略研究

运用动态视觉空间工作记忆任务探讨了飞行员和对照组的动态空间表征的建构特征。从两个方面考察策略运用:(1)在客体运动轨迹表征反应选择项上,根据客体运动轨迹的几何特征将选择项设置为整体型策略和局部型策略;(2)有关策略运用的问卷测试。结果发现,在完成运动轨迹的动态工作记忆时,飞行员更多采用整体策略,控制组更多采用局部。结果提示具有较高空间能力的飞行员在合并运动刺激元素、整合客体表征转化为整体表征时具有优势。最后提出延时动态空间表征表达运动客体运动轨迹表征,其空间构型依赖于一段时间的客体运动特性的积累。     

On the perception of shape from shading

The extraction of three-dimensional shape from shading is one of the most perceptually compelling, yet poorly understood, aspects of visual perception. In this paper, we report several new experiments on the manner in which the perception of shape from shading interacts with other visual processes such as perceptual grouping, preattentive search (“pop-out”), and motion perception. Our specific findings are as follows: (1) The extraction of shape from shading information incorporates at least two “assumptions” or constraints—first,that there is a single light source illuminating the whole scene, and second, that the light is shining from “above” in relation to retinal coordinates. (2) Tokens defined by shading can serve as a basis for perceptual grouping and segregation. (3) Reaction time for detecting a single convex shape does not increase with the number of items in the display. This “pop-out” effect must be based on shading rather than on differences in luminance polarity, since neither left-right differences nor step changes in luminance resulted in pop-out. (4) When the subjects were experienced, there were no search asymmetries for convex as opposed to concave tokens, but when the subjects were naive, cavities were much easier to detect than convex shapes. (5) The extraction of shape from shading can also provide an input to motion perception. And finally, (6) the assumption of “overhead illumination” that leads to perceptual grouping depends primarily on retinal rather than on “phenomenal” or gravitational coordinates. Taken collectively, these findings imply that the extraction of shape from shading is an “early” visual process that occurs prior to perceptual grouping, motion perception, and vestibular (as well as “cognitive”) correction for head tilt. Hence, there may be neural elements very early in visual processing that are specialized for the extraction of shape from shading.     

On the perception of shape from shading.

The extraction of three-dimensional shape from shading is one of the most perceptually compelling, yet poorly understood, aspects of visual perception. In this paper, we report several new experiments on the manner in which the perception of shape from shading interacts with other visual processes such as perceptual grouping, preattentive search ("pop-out"), and motion perception. Our specific findings are as follows: (1) The extraction of shape from shading information incorporates at least two "assumptions" or constraints--first, that there is a single light source illuminating the whole scene, and second, that the light is shining from "above" in relation to retinal coordinates. (2) Tokens defined by shading can serve as a basis for perceptual grouping and segregation. (3) Reaction time for detecting a single convex shape does not increase with the number of items in the display. This "pop-out" effect must be based on shading rather than on differences in luminance polarity, since neither left-right differences nor step changes in luminance resulted in pop-out. (4) When the subjects were experienced, there were no search asymmetries for convex as opposed to concave tokens, but when the subjects were naive, cavities were much easier to detect than convex shapes. (5) The extraction of shape from shading can also provide an input to motion perception. And finally, (6) the assumption of "overhead illumination" that leads to perceptual grouping depends primarily on retinal rather than on "phenomenal" or gravitational coordinates. Taken collectively, these findings imply that the extraction of shape from shading is an "early" visual process that occurs prior to perceptual grouping, motion perception, and vestibular (as well as "cognitive") correction for head tilt. Hence, there may be neural elements very early in visual processing that are specialized for the extraction of shape from shading.     

Perceptual organization of apparent motion in the Ternus display

A typical Ternus display has three sequentially presented frames, in which frame 1 consists of three motion tokens, frame 2 (blank) defines the interstimulus interval, and frame 3 has similar motion tokens with their relative positions shifted to the right. Interestingly, what appears to be a seemingly simple arrangement of stimuli can induce one of two distinct apparent-motion percepts in the observer. The first is an element-motion perception where the left-end token is seen to jump over its two neighboring tokens (inner tokens) to the right end of the display. The second is a group-motion perception where the entire display of the three tokens is seen to move to the right. How does the visual system choose between these two apparent-motion perceptions? It is hypothesized that the choice of motion perception is determined in part by the perceptual organization of the motion tokens. Specifically, a group-motion perception is experienced when a strong grouping tendency exists among the motion tokens belonging to the same frame. Conversely, an element-motion perception is experienced when a strong grouping tendency exists between the inner motion tokens in frames 1 and 3 (i.e. the two tokens that overlap in space between frames). We tested this hypothesis by varying the perceptual organization of the motion tokens. Both spatial (form similarity, 3-D proximity, common surface/common region, and occlusion) and temporal (motion priming) factors of perceptual organization were tested. We found that the apparent-motion perception of the Ternus display can be predictably affected, in a manner consistent with the perceptual organization hypothesis.