Redundancy effects in the perception and memory of visual objects

Is visual representation of an object affected by whether surrounding objects are identical to it, different from it, or absent? To address this question, we tested perceptual priming, visual short-term, and long-term memory for objects presented in isolation or with other objects. Experiment 1 used a priming procedure, where the prime display contained a single face, four identical faces, or four different faces. Subjects identified the gender of a subsequent probe face that either matched or mismatched with one of the prime faces. Priming was stronger when the prime was four identical faces than when it was a single face or four different faces. Experiments 2 and 3 asked subjects to encode four different objects presented on four displays. Holding memory load constant, visual memory was better when each of the four displays contained four duplicates of a single object, than when each display contained a single object. These results suggest that an object's perceptual and memory representations are enhanced when presented with identical objects, revealing redundancy effects in visual processing.     

A visual short-term memory advantage for faces

What determines how much can be stored in visual short-term memory (VSTM)? Studies of VSTM have focused largely on stimulus-based properties such as the number or complexity of the items stored. Recent work also suggests that capacity is severely reduced for items within the same category. However, the importance for VSTM capacity of more qualitative differences in processing for different categories has not been investigated. For example, faces are processed more holistically than other objects. In Experiments 1 and 2, we show that the processing of faces, objects that are crucial socially and for which we possess considerable expertise, overcomes these limitations. More faces can be stored in VSTM than objects from other complex nonface categories. As in prior studies, at short encoding durations we found that capacity for faces was less than that for other categories. However, at longer encoding durations, capacity for faces exceeded that for nonface objects, and this advantage was specific to upright faces. Because inversion reduces holistic processing, the interaction of orientation with VSTM capacity—which occurred for faces but not objects in Experiment 3—suggests that it is holistic processing that confers an advantage for face VSTM when sufficient encoding time is allowed.     

本族和异族面孔的视觉工作记忆容量:面孔特征的影响

采用延迟探测刺激匹配再认任务,考察面孔种族和内外部特征是否会影响面孔视觉工作记忆容量。被试先识记2或4张中国人或白人的真实面孔图片,一半有内部特征(眼睛、鼻子和嘴巴),另一半有内部和外部特征(脸型、发型),再进行面孔再认判断。采用Cowan’s K值的分析显示,我国被试对本族和异族面孔的视觉工作记忆容量没有差异,但面孔数量与特征多少会影响面孔工作记忆容量,表明对本族和异族面孔的视觉加工不同。     

Expertise for upright faces improves the precision but not the capacity of visual working memory

Considerable research has focused on how basic visual features are maintained in working memory, but little is currently known about the precision or capacity of visual working memory for complex objects. How precisely can an object be remembered, and to what extent might familiarity or perceptual expertise contribute to working memory performance? To address these questions, we developed a set of computer-generated face stimuli that varied continuously along the dimensions of age and gender, and we probed participants’ memories using a method-of-adjustment reporting procedure. This paradigm allowed us to separately estimate the precision and capacity of working memory for individual faces, on the basis of the assumptions of a discrete capacity model, and to assess the impact of face inversion on memory performance. We found that observers could maintain up to four to five items on average, with equally good memory capacity for upright and upside-down faces. In contrast, memory precision was significantly impaired by face inversion at every set size tested. Our results demonstrate that the precision of visual working memory for a complex stimulus is not strictly fixed but, instead, can be modified by learning and experience. We find that perceptual expertise for upright faces leads to significant improvements in visual precision, without modifying the capacity of working memory.     

Not all visual memories are created equal

Two experiments examined how well the long-term visual memories of objects that are encountered multiple times during visual search are updated. Participants searched for a target two or four times (e.g., white cat) among distractors that shared the target's colour, category, or were unrelated while their eye movements were recorded. Following the search, a surprise visual memory test was given. With additional object presentations, only target memory reliably improved; distractor memory was unaffected by the number of object presentations. Regression analyses using the eye movement variables as predictors indicated that number of object presentations predicted target memory with no additional impact of other viewing measures. In contrast, distractor memory was best predicted by the viewing pattern on the distractor objects. Finally, Experiment 2 showed that target memory was influenced by number of target object presentations, not number of searches for the target. Each of these experiments demonstrates visual memory differences between target and distractor objects and may provide insight into representational differences in visual memory.     

Eccentricity biases of object categories are evident in visual working memory

In high-order object areas, face-selective areas prefer centrally presented stimuli, whereas building-selective areas prefer peripherally presented stimuli (Levy et al., 2001). We investigated whether this eccentricity bias was also evident in visual working memory. In Experiment 1, we found that working memory performance for faces decreased towards the periphery while the performance for buildings remained unchanged across different eccentricities. To rule out the possibility that lower level features influence these results, we manipulated the spatial frequency of faces and buildings (Experiment 2) and the spatial layout information of the buildings (Experiment 3). In both of the experiments, we replicated the results of Experiment 1, even when these lower level features of stimuli were controlled. Consistent with previous findings, the current results suggest that each object category is processed in a different manner depending on the eccentricity. This eccentricity bias is likely the result of how the high-order object areas represent different object categories.     

Duration of cats' (Felis catus) working memory for disappearing objects

This study explored the duration of cats' working memory for hidden objects. Twenty-four cats were equally divided into four groups, which differed according to the type of visual cues displayed on and/or around the hiding boxes. During eight sessions, the four groups of cats were trained to locate a desirable object hidden behind one of the four boxes placed in front of them. Then, the cats were tested with retention intervals of 0, 10, 30 and 60 s. Results revealed no significant differences between the groups during training or testing. In testing, the cats' accuracy to locate the hidden object rapidly declined between 0 and 30 s but remained higher than chance with delays of up to 60 s. The analysis of errors also indicated that the cats searched as a function of the proximity of the target box and were not subjected to intertrial proactive interference. This experiment reveals that the duration of cats' working memory for disappearing objects is limited and the visual cues displayed on and/or around the boxes do not help the cats to memorize a hiding position. In discussion, we explore why the duration of cats' working memory for disappearing objects rapidly declined and compare these finding with those from domestic dogs. The irrelevance of visual cues displayed on and around the hiding boxes on cats' retention capacity is also discussed.     

Visual working memory for line orientations and face identities

Previous studies have shown that the number of objects we can actively hold in visual working memory is smaller for more complex objects. However, complex objects are not just more complex but are often more similar to other complex objects used as test probes. To separate effects of complexity from effects of similarity, we measured visual memory following a 1-sec delay for complex and simple objects at several levels of memory-to-test similarity. When memory load was one object, memory accuracy for a face (a complex attribute) was similar to a line orientation (a simple attribute) when the face changed in steps of 10% along a morphing continuum and the line changed in steps of 5° in orientation. Performance declined with increasing memory load and increasing memory-to-test similarity. Remarkably, when memory load was three or four objects, face memory was better than orientation memory at similar changed steps. These results held when memory for line orientations was compared with that for inverted faces. We conclude that complex objects do not always exhaust visual memory more quickly than simple objects do.     

Object categorisation,object naming,and viewpoint independence in visual remembering: Evidence from young children's drawings of a novel object

A simple object-drawing task confirms a three-way association between object categorisation, viewpoint independence, and longer-term visual remembering. Young children (5- to 7-year-olds) drew a familiar object or a novel object, immediately after it had been hidden from view or on the following day. Both objects were shown from a full range of viewpoints or from just two viewpoints, from neither of which would either object normally be drawn after unrestricted viewing. When drawing from short-term memory after restricted viewing, both objects were most likely to be depicted from a seen viewpoint. When drawing from longer-term memory after restricted viewing, the novel object continued to be drawn from a seen viewpoint, but the mug was now most likely to be drawn from a preferred viewpoint from which it had not been seen. Naming the novel object with a novel count noun (“Look at this. This is a dax”), to signal that it belonged to an object category, resulted in it being drawn in the same way as the familiar object. The results concur with other evidence indicating that short-term and longer-term visual remembering are differentially associated with viewpoint-dependent representations of individual objects and viewpoint independent representations of object categories, respectively.     

Object naming induces reliance on orientation-independent representations during longer-term, but not short-term, visual remembering

Naming novel objects with novel count nouns changes how the objects are drawn from memory, revealing that object categorisation induces reliance on orientation-independent visual representations during longer-term remembering, but not during short-term remembering. Serial position effects integrate this finding with a more established conceptualisation of short-term and longer-term visual remembering in which the former is identified as keeping an item in mind. Adults were shown a series of four novel objects in orientations in which they would not normally be drawn from memory. When not named ("Look at this object"), the objects were drawn in the orientations in which they had been seen. When named with a novel count noun (e.g., "Look at this dax"), the final object continued to be depicted in the orientation in which it had been seen, but all other objects were depicted in an unseen but preferred (canonical) orientation, even though participants could still remember the orientations in which they had been seen. Although orientation-dependent exemplar representations appear to be more accessible than orientation-independent generic representations during short-term remembering, the reverse is the case during longer-term remembering. How the theoretical framework emerging from these observations accommodates a broader body of evidence is discussed.     

Visual working memory for simple and complex visual stimuli

Does the magical number four characterize our visual working memory (VWM) capacity for all kinds of objects, or is the capacity of VWM inversely related to the perceptual complexity of those objects? To find out how perceptual complexity affects VWM, we used a change detection task to measure VWM capacity for six types of stimuli of different complexity: colors, letters, polygons, squiggles, cubes, and faces. We found that the estimated capacity decreased for more complex stimuli, suggesting that perceptual complexity was an important factor in determining VWM capacity. However, the considerable correlation between perceptual complexity and VWM capacity declined significantly if subjects were allowed to view the sample memory display longer. We conclude that when encoding limitations are minimized, perceptual complexity affects, but does not determine, VWM capacity.     

Object categorisation, object naming, and viewpoint independence in visual remembering: evidence from young children's drawings of a novel object

A simple object-drawing task confirms a three-way association between object categorisation, viewpoint independence, and longer-term visual remembering. Young children (5- to 7-year-olds) drew a familiar object or a novel object, immediately after it had been hidden from view or on the following day. Both objects were shown from a full range of viewpoints or from just two viewpoints, from neither of which would either object normally be drawn after unrestricted viewing. When drawing from short-term memory after restricted viewing, both objects were most likely to be depicted from a seen viewpoint. When drawing from longer-term memory after restricted viewing, the novel object continued to be drawn from a seen viewpoint, but the mug was now most likely to be drawn from a preferred viewpoint from which it had not been seen. Naming the novel object with a novel count noun ("Look at this. This is a dax"), to signal that it belonged to an object category, resulted in it being drawn in the same way as the familiar object. The results concur with other evidence indicating that short-term and longer-term visual remembering are differentially associated with viewpoint-dependent representations of individual objects and viewpoint independent representations of object categories, respectively.     

Object specificity and personal relevance in long-term visual remembering

The personal relevance of an object is multi-faceted, each facet being capable of contributing to the effects on object memory attributed to personal relevance. An object's status as an individual object (object specificity), rather than just a category of object, is one such facet and its impact on the long-term visual remembering of everyday objects is assessed in two experiments. Images and drawings were produced under generic (e.g., “Please draw a bed”) and personal exemplar (e.g., “Please draw your bed”) instructions, and participants indicated the degree to which the image on which their drawing was based was of a specific object or a generic object. Object specificity induced a sense of time and place for a remembered object, the most recent encounter with the object being most salient. Other aspects of personal relevance collectively facilitated the retrieval of an object's category-irrelevant features (thereby increasing the vividness of the object image), the other objects with which it was seen, and a more general episodic sense of place. Against a broader theoretical perspective, it is proposed that visual episodic memory and visual knowledge are primary sources of information for specific personally relevant objects and generic objects, respectively.     

When do spatial and visual working memory interact?

This study examined how spatial working memory and visual (object) working memory interact, focusing on two related questions: First, can these systems function independently from one another? Second, under what conditions do they operate together? In a dual-task paradigm, participants attempted to remember locations in a spatial working memory task and colored objects in a visual working memory task. Memory for the locations and objects was subject to independent working memory storage limits, which indicates that spatial and visual working memory can function independently from one another. However, additional experiments revealed that spatial working memory and visual working memory interact in three memory contexts: when retaining (1) shapes, (2) integrated color-shape objects, and (3) colored objects at specific locations. These results suggest that spatial working memory is needed to bind colors and shapes into integrated object representations in visual working memory. Further, this study reveals a set of conditions in which spatial and visual working memory can be isolated from one another.     

Perceptual expertise enhances the resolution but not the number of representations in working memory

Despite its central role in cognition, capacity in visual working memory is restricted to about three or four items. Curby and Gauthier (2007) examined whether perceptual expertise can help to overcome this limit by enabling more efficient coding of visual information. In line with this, they observed higher capacity estimates for upright than for inverted faces, suggesting that perceptual expertise enhances visual working memory. In the present work, we examined whether the improved capacity estimates for upright faces indicates an increased number of "slots" in working memory, or improved resolution within the existing slots. Our results suggest that perceptual expertise enhances the resolution but not the number of representations that can be held in working memory. These results clarify the effects of perceptual expertise in working memory and support recent suggestions that number and resolution represent distinct facets of working memory ability.     

客体在视觉工作记忆中的存储机制

采用变化觉察范式,通过两个实验对不同类型视觉信息在工作记忆中的存储机制进行了探讨。实验一中要求记忆的客体由颜色和形状两基本特征构成;实验二中的客体为具有不同颜色及开口朝向的兰道环。通过观察检测项变化方式对记忆绩效的影响,获得以下结论:（1）对颜色和形状两基本特征的存储以整合客体为单位;（2）兰道环的颜色与开口朝向信息难以以整合客体方式存储。笔者推测,视觉工作记忆中存储的整合客体并非如现有理论假设的,是在集中注意参与下创建的,而是由并行加工阶段所获信息构成;客体中所含需集中注意提取的细节特征信息难以与其基本特征信息整合于该客体表征     

Feature binding in visual working memory evaluated by type identification paradigm

Memory for feature binding comprises a key ingredient in coherent object representations. Previous studies have been equivocal about human capacity for objects in the visual working memory. To evaluate memory for feature binding, a type identification paradigm was devised and used with a multiple-object permanence tracking task. Using objects defined by shape and color, observers identified types of changes in feature combinations across an occlusion event, and the effects of object motion and number of switches were investigated. With only one switch, task performance was impaired even under stationary conditions, suggesting highly limited capacity of binding memory. Second switch improved performance only in the stationary condition, suggesting that object motion strongly disrupts feature binding. Further analyses and experiments suggest that improvement by the second switch reflects transition of binding memory by selective attention.     

Constructing visual representations of natural scenes: the roles of short- and long-term visual memory

A "follow-the-dot" method was used to investigate the visual memory systems supporting accumulation of object information in natural scenes. Participants fixated a series of objects in each scene, following a dot cue from object to object. Memory for the visual form of a target object was then tested. Object memory was consistently superior for the two most recently fixated objects, a recency advantage indicating a visual short-term memory component to scene representation. In addition, objects examined earlier were remembered at rates well above chance, with no evidence of further forgetting when 10 objects intervened between target examination and test and only modest forgetting with 402 intervening objects. This robust prerecency performance indicates a visual long-term memory component to scene representation.     

The effects of prelimbic and infralimbic lesions on working memory for visual objects in rats.

The present experiment investigated the effects of quinolinic acid (90 mM) lesions of the prelimbic-infralimbic cortices on working memory for visual objects and on acquisition of a visual object discrimination. In both tests a GO/NO-GO procedure was used. In the working memory task, rats were tested before and after surgery. A continuous recognition procedure was used to assess working memory, which involved successive exposure to different three-dimensional objects that could be displaced to receive a cereal reinforcement. Of the 12 object presentations/session, 4 objects were presented for a second time in which displacing the object did not result in a reinforcement. The number of trials between the first and second presentations of an object ranged from 0 to 3 (lags). Memory was assessed by the latency to displace an object during the second presentation. In the visual object discrimination, rats had successive exposure to two different objects. Displacement of one object resulted in a cereal reinforcement, while displacement of the other did not. The findings indicated that prelimbic-infralimbic lesions significantly impaired memory for visual objects across all lags. Prelimbic-infralimbic lesions did not impair acquisition of the visual object discrimination. The results suggest that the prelimbic-infralimbic areas are part of neural system important in the short-term memory for visual objects.     

Multidimensional shape similarity in the development of visual object classification

The current work examined age differences in the classification of novel object images that vary in continuous dimensions of structural shape. The structural dimensions employed are two that share a privileged status in the visual analysis and representation of objects: the shape of discrete prominent parts and the attachment positions of those parts. Experiment 1 involved a triad classification task in which participants at each of three different ages (5 years, 8 years, and adult) classified object images from two distinct stimulus sets. Across both sets, the youngest children demonstrated a systematic bias toward the shape of discrete parts during their judgments. With increasing age, participants increasingly came to select both the shape and the position of parts when classifying the images. The findings from Experiment 2 indicate that the local shape bias observed in young children's classifications is not merely a consequence of a discrimination advantage for that dimension. Results are discussed in relation to corresponding age-related changes in other functional contexts of visual processing.