Long-term retinotopic priming in object identification

An important result in perception research is that priming in an object naming task is invariant with translation and left-right reflection. A more sensitive object recognition paradigm was used in three experiments in order to investigate the extent to which priming of object identification is affected by changes in left-right orientation and position. In a prime phase, participants viewed consecutively presented object images. In a subsequent probe phase, participants identified familiar objects in rapid visual streams of nonobject distractors. In Experiment 1, images previously viewed in the same left-right orientation were primed more than images previously viewed in the opposite orientation (i.e., a left-right reflection). This reflection-sensitive priming was replicated in Experiment 2 using a brief (300-msec) prime exposure. In Experiment 3, when the retinal locations of prime and probe images matched, reflection-sensitive priming was also obtained, but when the retinal locations of prime and probe images differed, no reflection-sensitive priming was observed. These results suggest that a single prime exposure can produce long-term priming that is sensitive to left-right reflection, but that this priming is specific to a retinal location.     

Evidence for complete translational and reflectional invariance in visual object priming.

The magnitude of priming on naming reaction times and on the error rates, resulting from the perception of a briefly presented picture of an object approximately 7 min before the primed object, was found to be independent of whether the primed object was originally viewed in the same hemifield, left-right or upper-lower, or in the same left-right orientation. Performance for same-name, different-examplar images was worse than for identical images, indicating that not only was there priming from block one to block two, but that some of the priming was visual, rather than purely verbal or conceptual. These results provide evidence for complete translational and reflectional invariance in the representation of objects for purposes of visual recognition. Explicit recognition memory for position and orientation was above chance, suggesting that the representation of objects for recognition is independent of the representations of the location and left-right orientation of objects in space.     

Evidence for holistic representations of ignored images and analytic representations of attended images

According to the hybrid theory of object recognition (J. E. Hummel, 2001), ignored object images are represented holistically, and attended images are represented both holistically and analytically. This account correctly predicts patterns of visual priming as a function of translation, scale (B. J. Stankiewicz & J. E. Hummel, 2002), and left-right reflection (B. J. Stankiewicz, J. E. Hummel, & E. E. Cooper, 1998). The model also predicts that priming for attended images will generalize over configural distortions (split images), whereas priming for ignored images will not. Three experiments tested and confirmed this prediction. Split images visually primed their intact and split counterparts when they were attended but not when they were ignored, whereas intact images primed themselves whether they were attended or not. The data contribute to the growing body of evidence that 1 function of visual attention is to permit the generation of explicitly relational representations of object shape.     

Size and reflection effects in priming: A test of transfer-appropriate processing

Prior research has suggested that priming on perceptual implicit tests is insensitive to changes in stimulus size and reflection. The present experiments were performed to investigate whether size and reflection effects can be obtained in priming under conditions that encourage the processing of this information at study and at test, as predicted by transfer-appropriate processing. The results indicate that priming was affected by a change in the physical size of an object when study and test tasks required a judgment about the real size of pictorial objects (e.g., deciding whether a zebra presented small or large on the screen was larger or smaller than a typical chair), and when the test task required the identification of fragmented pictures. However, a change in left-right orientation had no effect on priming when study and test tasks required a judgment about the left-right orientation of familiar objects, or when the test task involved the identification of fragmented pictures. This difference between size and reflection effects is discussed in terms of the differential importance of size and reflection information in shape identification.     

Visually guided grasping of common objects: Effects of priming

Priming effects were tested on the planning of the grasping of common objects under full vision during action performance. Healthy participants took part in four experiments which manipulated the nature of the prime (objects, circular block, rectangular bar) and priming context (blocked vs. mixed). Each experiment relied on four priming conditions: (1) congruent orientation, (2) incongruent orientation, (3) neutral prime, and (4) no prime. Priming was observed to have a facilitating effect on visually guided grasping when the object to be grasped was primed by a congruently oriented identical object. This effect was rather independent of the priming context (experimental set-up). Our data suggest an object's functional identity may contribute to the priming effect, as well as its intrinsic (e.g., shape, size) and extrinsic (orientation) visual characteristics. We showed that the planning of visually guided grasping is influenced by prior visual experience, and thus that grasping is not based exclusively on real-time processing of visual information.     

Does the brain's ventral visual pathway compute object shape?

A rich behavioral literature has shown that human object recognition is supported by a representation of shape that is tolerant to variations in an object's appearance. Such 'global' shape representations are achieved by describing objects via the spatial arrangement of their local features, or structure, rather than by the appearance of the features themselves. However, accumulating evidence suggests that the ventral visual pathway – the primary substrate underlying object recognition – may not represent global shape. Instead, ventral representations may be better described as a basis set of local image features. We suggest that this evidence forces a reevaluation of the role of the ventral pathway in object perception and posits a broader network for shape perception that encompasses contributions from the dorsal pathway.     

Object-position binding in visual memory for natural scenes and object arrays

Nine experiments examined the means by which visual memory for individual objects is structured into a larger representation of a scene. Participants viewed images of natural scenes or object arrays in a change detection task requiring memory for the visual form of a single target object. In the test image, 2 properties of the stimulus were independently manipulated: the position of the target object and the spatial properties of the larger scene or array context. Memory performance was higher when the target object position remained the same from study to test. This same-position advantage was reduced or eliminated following contextual changes that disrupted the relative spatial relationships among contextual objects (context deletion, scrambling, and binding change) but was preserved following contextual change that did not disrupt relative spatial relationships (translation). Thus, episodic scene representations are formed through the binding of objects to scene locations, and object position is defined relative to a larger spatial representation coding the relative locations of contextual objects.     

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.     

Priming and Recognition of Human Motion Patterns

Left-right orientation and size incongruence is known to affect recognition memory for objects but not object priming. In the present study, the effects of study-test changes in left-right orientation and size on old-new recognition decisions and long-term priming of human motion patterns were examined. Experiment 1 showed effects of orientation incongruence on both recognition and priming. Experiment 2 showed an effectof size incongruence on recognition memory but not on priming. It is suggested that the representations of human actions that underlie human motion priming are on a level that preserve orientation, possibly because of the importance of dynamic information for perceiving motion patterns or because encoding of human motion is governed by a body schema (e.g. Reed & Farah, 1995). In contrast, low-level metric information such as size is inconsequential to priming because priming involves identification of shape, which is not affected by size transformations. The effect of size on recognition memory, on the other hand, shows thatexplicitrecognition decisions may draw on any available episodic information, including metric attributes, to make an old new discrimination.     

The effect of body and part-based motion on the recognition of unfamiliar objects

We investigated the role of global (body) and local (parts) motion on the recognition of unfamiliar objects. Participants were trained to categorise moving objects and were then tested on their recognition of static images of these targets using a priming paradigm. Each static target shape was primed by a moving object that comprised either the same body and parts motion; same body, different parts motion; different body, same part motion as the learned target or was non-moving. Only the same body but not the same part motion facilitated shape recognition (Experiment 1), even when either motion was diagnostic of object identity (Experiment 2). When parts motion was more related to the object's body motion then it facilitated the recognition of the static target (Experiment 3). Our results suggest that global and local motions are independently accessed during object recognition and have important implications for how objects are represented in memory.     

The influence of task requirements on priming in object decision and matching

We argue that task requirements can be the determinant in generating different results in studies on visual object recognition. We investigated priming for novel visual objects in three implicit memory tasks. A study-test design was employed in which participants first viewed line drawings of unfamiliar objects and later made different decisions about structural aspects of the objects. Priming for both symmetric and asymmetric possible objects was observed in a task requiring a judgment of structural possibility. However, when the task was changed to one requiring a judgment of structural symmetry, only symmetric possible objects showed priming. Finally, in a matching task in which participants made a same-different judgment, only symmetric possible objects exhibited priming. These results suggest that an understanding of object representation will be most fruitful if it is based on careful analyses of both the task demands and their interaction(s) with encoding and retrieval processes.     

Priming contour-deleted images: evidence for intermediate representations in visual object recognition

The speed and accuracy of perceptual recognition of a briefly presented picture of an object is facilitated by its prior presentation. Picture priming tasks were used to assess whether the facilitation is a function of the repetition of: (a) the object's image features (viz., vertices and edges), (b) the object model (e.g., that it is a grand piano), or (c) a representation intermediate between (a) and (b) consisting of convex or singly concave components of the object, roughly corresponding to the object's parts. Subjects viewed pictures with half their contour removed by deleting either (a) every other image feature from each part, or (b) half the components. On a second (primed) block of trials, subjects saw: (a) the identical image that they viewed on the first block, (b) the complement which had the missing contours, or (c) a same name-different exemplar of the object class (e.g., a grand piano when an upright piano had been shown on the first block). With deletion of features, speed and accuracy of naming identical and complementary images were equivalent, indicating that none of the priming could be attributed to the features actually present in the image. Performance with both types of image enjoyed an advantage over that with the different exemplars, establishing that the priming was visual rather than verbal or conceptual. With deletion of the components, performance with identical images was much better than that with their complements. The latter were equivalent to the different exemplars, indicating that all the visual priming of an image of an object is through the activation of a representation of its components in specified relations. In terms of a recent neural net implementation of object recognition (Hummel & Biederman, in press), the results suggest that the locus of object priming may be at changes in the weight matrix for a geon assembly layer, where units have self-organized to represent combinations of convex or singly concave components (or geons) and their attributes (e.g., aspect ratio, orientation, and relations with other geons such as TOP-OF). The results of these experiments provide evidence for the psychological reality of intermediate representations in real-time visual object recognition.     

Potentiation of action by undetected affordant objects

The physical attributes of objects that are relevant to motor behaviour, or action, are referred to as affordances (Gibson, 1979). Recent evidence has shown that an object's affordance can potentiate an unrelated motor response even when there is no intention to respond to it (e.g., Tucker & Ellis, 1998). In the five experiments, we examined whether conscious perception of an affordance is necessary to produce motor priming by presenting images of affordant objects (e.g., hammer) under conditions which cause them to be undetectable: Brief masked exposure (BME) and attentional blink (AB). We successfully demonstrated that conscious perception is not necessary for an object's affordance to produce motor priming. Since these findings are consistent with the abilities/disabilities of patients with blindsight and visual form agnosia, it is possible that processing accomplished by the dorsal stream produced this effect, though more research is needed to confirm this assertion.     

A mere exposure effect for transformed three-dimensional objects: Effects of reflection, size, or color changes on affect and recognition

If the mere exposure effect is based on implicit memory, recognition and affect judgments should be dissociated by experimental variables in the same manner as other explicit and implicit measures. Consistent with results from recognition and picture naming or object decision priming tasks (e.g., Biederman & E. E. Cooper, 1991, 1992; L. A. Cooper, Schacter, Ballesteros, & Moore, 1992), the present research showed that recognition memory but not affective preference was impaired by reflection or size transformations of three-dimensional objects between study and test. Stimulus color transformations had no effect on either measure. These results indicate that representations that support recognition memory code spatial information about an object’s left-right orientation and size, whereas representations that underlie affective preference do not. Insensitivity to surface feature changes that do not alter object form appears to be a general characteristic of implicit memory measures, including the affective preference task.     

The time course of object encoding

Four experiments examined the effects of encoding time on object identification priming and recognition memory. After viewing objects in a priming phase, participants identified objects in a rapid stream of non-object distracters; display times were gradually increased until the objects could be identified (Experiments 1-3). Participants also made old/new recognition judgments about previously viewed objects (Experiment 4). Reliable priming for object identification occurred with 150 ms of encoding and reached a maximum after about 300 ms of encoding time. In contrast, reliable recognition judgments occurred with 75 ms of encoding and continued to improve for encoding times of up to 1200 ms. These results suggest that recognition memory may be based on multiple levels of object representation, from rapidly activated representations of low-level features to semantic knowledge associated with the object. In contrast, priming in this object identification task may be tied specifically to the activation of representations of object shape.     

The role of attention and study time in explicit and implicit memory for unfamiliar visual stimuli

The effects of limited attentional resources and study time on explicit and implicit memory were studied using Schacter and Cooper’s possible and impossible objects in their recognition and object decision paradigm. In one experiment, when attention at study was limited by a flanking digits procedure, object recognition was diminished but object decision priming for possible objects was unaffected; in another experiment, limiting attention plus reducing stimulus study time impaired object recognition and eliminated object priming. Recognition memory and perceptual priming for previously unfamiliar visual stimuli were both influenced by attention, although to different degrees. The intervening variable of study time determined the degree to which priming was affected by attentional resources. These results support a limited capacity attentional model for both recognition and perceptual priming of unfamiliar visual stimuli, and they highlight the need for assessing the interaction of attentional resources and study time in explicit and implicit memory tasks.     

Visual and tactile memory for 2-D patterns: Effects of changes in size and left-right orientation

Visual identification of 3-D objects depends on representations that are invariant across changes in size and left-right orientation. We examined whether this finding reflects the unique demands of processing 3-D objects, or whether it generalizes to 2-D patterns and to the tactile modality. Our findings suggest that object representation for identification is influenced greatly by the processing demands of stimulus materials (e.g., 2-D vs. 3-D objects) and stimulus modality (touch vs. vision). Identification of 2-D patterns in vision is adversely affected by left-right orientation changes, but not size changes. Identification of the same patterns in touch is adversely affected by both changes. Together, the results suggest that the unique processing demands of stimulus materials and modality shape the representation of objects in memory.     

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.