Coordinate transformations in object recognition.

A basic problem of visual perception is how human beings recognize objects after spatial transformations. Three central classes of findings have to be accounted for: (a) Recognition performance varies systematically with orientation, size, and position; (b) recognition latencies are sequentially additive, suggesting analogue transformation processes; and (c) orientation and size congruency effects indicate that recognition involves the adjustment of a reference frame. All 3 classes of findings can be explained by a transformational framework of recognition: Recognition is achieved by an analogue transformation of a perceptual coordinate system that aligns memory and input representations. Coordinate transformations can be implemented neurocomputationally by gain (amplitude) modulation and may be regarded as a general processing principle of the visual cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactions between symmetry and elongation in determining reference frames for object perception.

Many theories of object recognition posit that objects are encoded with respect to a perceptual frame of reference. Such theories assume that factors such as symmetry and elongation are critical for the assignment of an object's primary axis, and consequently for the extraction of an object's reference frame. The present experiments directly examined the relative roles played by symmetry and elongation in the determination of an object's primary axis, and the extent to which symmetry and elongation interact with one another. A total of 55 Ss (aged 15–27 yrs) participated in the experiments. The authors found that observers use both symmetry and elongation in extracting an object's primary axis, that the extent to which each cue dominates depends on its relative salience, and that symmetry and elongation are processed interactively, rather than in encapsulated modules. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decoupling object detection and categorization.

We investigated whether there exists a behavioral dependency between object detection and categorization. Previous work (Grill-Spector & Kanwisher, 2005) suggests that object detection and basic-level categorization may be the very same perceptual mechanism: As objects are parsed from the background they are categorized at the basic level. In the current study, we decouple object detection from categorization by manipulating the between-category contrast of the categorization decision. With a superordinate-level contrast with people as one of the target categories (e.g., cars vs. people), which replicates Grill-Spector and Kanwisher, we found that success at object detection depended on success at basic-level categorization and vice versa. But with a basic-level contrast (e.g., cars vs. boats) or superordinate-level contrast without people as a target category (e.g., dog vs. boat), success at object detection did not depend on success at basic-level categorization. Successful object detection could occur without successful basic-level categorization. Object detection and basic-level categorization do not seem to occur within the same early stage of visual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhinal cortex lesions and object recognition in rats.

Tested 11 male rats with bilateral lesions of lateral entorhinal cortex and perirhinal cortex on a nonrecurring-items delayed nonmatching-to-sample (DNMS) task resembling the one that is commonly used to study object recognition (OR) in monkeys. The rats were tested at retention delays of 4, 15, 60, 120, and 600 sec before and after surgery. After surgery, they displayed a delay-dependent deficit: They performed normally at the 4-sec delay but were impaired at delays of 15 sec or longer. The addition of bilateral amygdala lesions did not increase their DNMS deficits. The present finding of a severe DNMS deficit following rhinal cortex damage is consistent with the authors' previous finding that bilateral lesions of the hippocampus cause only mild DNMS deficits in rats unless there is also damage to rhinal cortex (D. G. Mumby et al, 1992). These findings add to accumulating evidence that the rhinal cortex, but not the amygdala, plays a critical role in OR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object recognition and object orientation in Alzheimer's disease.

There are a wide variety of neuropsychological deficits in Alzheimer's disease (AD), among which are disorders of visual perception and spatial cognition. The present study investigated the ability of 20 mildly to moderately deteriorated patients with AD (and 174 age- and education-matched controls) on tasks that required them to visually identify, provide the canonical orientation of, and mentally rotate common objects. Some 85% of the AD patients performed poorly on all tasks. The authors were able to identify a small number of individual patients whose pattern of performance represented double dissociations between recognizing objects and knowing their canonical orientation. These findings are interpreted in the context of previous findings, especially as to whether information relating to an object's orientation and identity is independently coded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are edges sufficient for object recognition?

The authors argue that the concept of "edges" as used in current research on object recognition obscures the significant difficulties involved in interpreting stimulus information. Edges have sometimes been operationalized as line drawings, which can be an invalid and misleading practice. A new method for evaluating the utility of edge information, operationalized as the outputs of a local, signal-based edge extractor, is introduced. With 1-s exposures, the accuracy of identifying objects in the edge images was found to be less than half that with color photographs. Therefore, edges are far from being sufficient for object recognition. Alternative approaches to the problem of interpreting stimulus information are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inferior temporal mechanisms for invariant object recognition

The specific size and retinal location of an object are readily perceived, yet recognition of an object's identity is hardly affected by transformations of its size or location. To explore how such stimulus transformations are treated by known mechanisms for visual short-term memory in inferior temporal (IT) cortex, IT cells were recorded in monkeys performing a delayed matching-to-sample task. The stimuli were pictures of complex objects, and the monkeys ignored differences in size and retinal location when matching the test items to the sample held in memory. The sensory information communicated by cells was assessed in their responses to the sample stimuli, and mnemonic information was assessed in their responses to the test stimuli. In the sensory domain, the ordering of relative stimulus preferences for nearly all cells was invariant over changes in size or location; however, some cells nonetheless preferred stimuli of a given size or location. In the mnemonic domain, the responses of many cells were modulated according to whether the test stimulus matched the sample held in memory, and these memory effects were invariant over the relative sizes and locations of the stimuli. Thus, IT neuronal populations may mediate not only the recognition and memory of object identity, which are invariant over size and location, but also the perception of the transformations themselves.     

Effects of outline shape in object recognition.

The use of outline shape in recognizing objects was investigated in 4 experiments. In Experiment 1, participants matched a shaded image to either another shaded image or a silhouette. In Experiment 2, they initially named shaded images; later they named either shaded images or silhouettes. Performance in both experiments was predicted by changes in the outline shape of the stimuli. The same matching (Experiment 3) and priming (Experiment 4) paradigms were then used to investigate recognition with objects that were rotated between presentations so as to change the outline shape of the object. Recognition was predicted by changes to outline shape. These results place constraints on models of object recognition and are most compatible with viewpoint-dependent models of recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unraveling mechanisms for expert object recognition: Bridging brain activity and behavior.

Behavioral sensitivity to object transformations and the response to novel objects (Greebles) in the fusiform face area (FFA) was measured several times during expertise training. Sensitivity to 3 transformations increased with expertise: (a) configural changes in which halves of objects were misaligned, (b) configural changes in which some of the object parts were moved, and (c) the substitution of an object part with a part from a different object. The authors found that holistic-configural effects can arise from object representations that are differentiated in terms of features or parts. Moreover, a holistic-inclusive effect was correlated with changes in the right FFA. Face recognition may not be unique in its reliance on holistic processing, measured in terms of both behavior and brain activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Color improves object recognition in normal and low vision.

Does color improve object recognition? If so, is the improvement greater for images with low spatial resolution in which there is less shape information? Do people with low visual acuity benefit more from color? Three experiments measured reaction time (RT) and accuracy for naming food objects displayed in 4 types of images: gray scale or color, and high or low spatial resolution (produced by blur). Normally sighted Ss had faster RTs with color, but the improvement was not significantly greater for images with low spatial resolution. Low vision Ss were also faster with color, but the difference did not depend significantly on acuity. In 2 additional experiments, it was found that the faster RTs for color stimuli were related to objects' prototypicality but not to their color diagnosticity. It was concluded that color does improve object recognition, and the mechanism is probably sensory rather than cognitive in origin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pyrithiamine-induced thiamine deficiency impairs object recognition in rats.

Pyrithiamine-induced thiamine deficiency (PTD) in rats is used to model the etiology, diencephalic neuropathology, and memory deficits of Korsakoff's amnesia. We assessed the performance of rats exposed to PTD on a test of object recognition—nonrecurring-items delayed nonmatching-to-sample (DNMS). PTD produced thalamic lesions similar to those of Korsakoff's amnesics and similar to those previously observed in PTD rats. PTD rats required more trials to master DNMS at a 4-sec retention delay than did controls, and after they had done so, they performed more poorly than controls at delays of 15, 30, 60, and 120 sec. DNMS deficits were also observed in PTD rats that received training prior to PTD treatment. These findings support the validity of the PTD rat model of Korsakoff's disease by demonstrating that PTD rats display object-recognition deficits that are similar to those reported in Korsakoff amnesics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of perceptual load in object recognition.

Predictions from perceptual load theory (Lavie, 1995, 2005) regarding object recognition across the same or different viewpoints were tested. Results showed that high perceptual load reduces distracter recognition levels despite always presenting distracter objects from the same view. They also showed that the levels of distracter recognition were unaffected by a change in the distracter object view under conditions of low perceptual load. These results were found both with repetition priming measures of distracter recognition and with performance on a surprise recognition memory test. The results support load theory proposals that distracter recognition critically depends on the level of perceptual load. The implications for the role of attention in object recognition theories are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Figure-ground organization and object recognition processes: An interactive account.

Traditional bottom-up models of visual processing assume that figure-ground organization precedes object recognition. This assumption seems logically necessary: How can object recognition occur before a region is labeled as figure? However, some behavioral studies find that familiar regions are more likely to be labeled figure than less familiar regions, a problematic finding for bottom-up models. An interactive account is proposed in which figure-ground processes receive top-down input from object representations in a hierarchical system. A graded, interactive computational model is presented that accounts for behavioral results in which familiarity effects are found. The interactive model offers an alternative conception of visual processing to bottom-up models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structural contingencies and object-based shifts of attention during object recognition.

A time-course contingency is a dependency between processing events during object recognition in which information processed early influences the efficiency of subsequent processing. Nine experiments provided evidence for 2 distinct types of contingencies with different time courses. Common feature primes and targets were presented successively and briefly in the same extrafoveal position and were masked (integration priming). When total stimulus duration was under 150 ms, structurally related primes facilitated identification more than less related primes—a structural contingency. When duration was above 300 ms, primes that attracted attention to the object as a whole facilitated identification and structural relatedness had little or no effect—a contingency involving object-based attention. The results are relevant to models of object recognition and a proposed progression of processes underlying scene perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does orientation-independent object recognition precede orientation-dependent recognition? Evidence from a cuing paradigm.

Object recognition may entail an incremental normalization process before access to canonical orientation representations, but is this process guided by prior access to object-centered representations? In Exp 1, the authors showed observers figure–ground stimuli known to reflect access to, and output from, stored shape representations. The stimuli appeared in each of 6 different orientations, preceded by cues providing either (1) no information, (2) upright shape information only, (3) upright shape information plus orientation information (separately), or (4) shape information in the same orientation as the upcoming figure–ground test stimulus. Contrary to predictions by a postaccess account, the cues failed to eliminate orientation dependency in shape recognition. Results favor a preaccess account of the normalization process within the context of canonical orientation representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic versus perceptual influences of color in object recognition.

The influence of color as a surface feature versus its influence as stored knowledge in object recognition was assessed. Participants decided whether a briefly presented and masked picture matched a test name. For pictures and words referring to similarly shaped objects, semantic color similarity (SCS) was present when picture and word shared the same prototypical color (e.g., purple apple followed by cherry). Perceptual color similarity (PCS) was present when the surface color of the picture matched the prototypical color of the named object (e.g., purple apple followed by blueberry). Response interference was primarily due to SCS, despite the fact that participants based similarity ratings on PCS. When uncolored objects were used, SCS interference still occurred, implying that the influence of SCS did not depend on the presence of surface color. The results indicate that, relative to surface color, stored color knowledge was more influential in object recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological evidence for visual- and motor-based affordance: Effects of reference frame and object–hand congruence.

Two experiments are reported that use patients with visual extinction to examine how visual attention is influenced by action information in images. In Experiment 1 patients saw images of objects that were either correctly or incorrectly colocated for action, with the objects held by hands that were congruent or incongruent with those used premorbidly by the patients. The images were also shown from a 1st- and 3rd-person perspective. There was an overall reduction in extinction for objects colocated for action. In addition, there was an extra benefit when the objects were held in hands congruent with those used by the patients and when the objects were seen from a 1st-person perspective. This last result fits with an effect of motor simulation, over and above a purely visual effect based on positioning objects correctly for action. Experiment 2 showed that effects of hand congruence could emerge with images depicted from a 3rd-person perspective when patients saw themselves holding the objects. The data indicate 2 effects of action information on extinction: (a) an effect of colocating objects for action, which does not depend on a self-reference frame (a visual effect), and (b) an effect sensitive to object–hand congruence, which does depend on a self-reference frame (a motor-based effect). The self-reference frame is induced when stimuli are viewed from a 1st-person perspective and when an image of the self is seen from a 3rd-person perspective. Both visual and motor-based effects of action information facilitate the spread of attention across objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic interference from visual object recognition on visual imagery.

A new technique for examining the interaction between visual object recognition and visual imagery is reported. The "image-picture interference" paradigm requires participants to generate and make a response to a mental image of a previously memorized object, while ignoring a simultaneously presented picture distractor. Responses in 2 imagery tasks (making left-right higher spatial judgments and making taller-wider judgments) were longer when the simultaneous picture distractor was categorically related to the target distractor relative to unrelated and neutral target-distractor combinations. In contrast, performance was not influenced in this way when the distractor was a related word, when a semantic categorization decision was made to the target, or when distractor and target were visually but not categorically related to one another. The authors discuss these findings in terms of the semantic representations shared by visual object recognition and visual imagery that mediate performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)