Long-term repetition priming and semantic interference in a lexical-semantic matching task: tapping the links between object names and colors.

Using a novel paradigm to engage the long-term mappings between object names and the prototypical colors for objects, we investigated the retrieval of object-color knowledge as indexed by long-term priming (the benefit in performance from a prior encounter with the same or a similar stimulus); a process about which little is known. We examined priming from object naming on a lexical-semantic matching task. In the matching task participants encountered a visually presented object name (Experiment 1) or object shape (Experiment 2) paired with either a color patch or color name. The pairings could either match whereby both were consistent with a familiar object (e.g., strawberry and red) or mismatch (strawberry and blue). We used the matching task to probe knowledge about familiar objects and their colors pre-activated during object naming. In particular, we examined whether the retrieval of object-color information was modality-specific and whether this influenced priming. Priming varied with the nature of the retrieval process: object-color priming arose for object names but not object shapes and beneficial effects of priming were observed for color patches whereas inhibitory priming arose with color names. These findings have implications for understanding how object knowledge is retrieved from memory and modified by learning.

The time course of activation of object shape and shape+colour representations during memory retrieval.

Little is known about the timing of activating memory for objects and their associated perceptual properties, such as colour, and yet this is important for theories of human cognition. We investigated the time course associated with early cognitive processes related to the activation of object shape and object shape+colour representations respectively, during memory retrieval as assessed by repetition priming in an event-related potential (ERP) study. The main findings were as follows: (1) we identified a unique early modulation of mean ERP amplitude during the N1 that was associated with the activation of object shape independently of colour; (2) we also found a subsequent early P2 modulation of mean amplitude over the same electrode clusters associated with the activation of object shape+colour representations; (3) these findings were apparent across both familiar (i.e., correctly coloured - yellow banana) and novel (i.e., incorrectly coloured - blue strawberry) objects; and (4) neither of the modulations of mean ERP amplitude were evident during the P3. Together the findings delineate the timing of object shape and colour memory systems and support the notion that perceptual representations of object shape mediate the retrieval of temporary shape+colour representations for familiar and novel objects.

Dissociating positive and negative influences of verbal processing on the recognition of pictures of faces and objects.

Four experiments investigated the role of verbal processing in the recognition of pictures of faces and objects. We used (a) a stimulus-encoding task where participants learned sequentially presented pictures in control, articulatory suppression, and describe conditions and then engaged in an old-new picture recognition test and (b) a poststimulus-encoding task where participants learned the stimuli without any secondary task and then either described or not a single item from memory before the recognition test. The main findings were as follows: First, verbalization influenced picture recognition. Second, there were contrasting influences of verbalization on the recognition of faces, compared with objects, that were driven by (a) the stage of processing during which verbalization took place (as assessed by the stimulus-encoding and poststimulus-encoding tasks), (b) whether verbalization was subvocal (whereby one goes through the motions of speaking but without making any sound) or overt, and (c) stimulus familiarity. During stimulus encoding there was a double dissociation whereby subvocal verbalization interfered with the recognition of faces but not objects, while overt verbalization benefited the recognition of objects but not faces. In addition, stimulus familiarity provided an independent and beneficial influence on performance. Post stimulus encoding, overt verbalization interfered with the recognition of both faces and objects, and this interference was apparent for unfamiliar but not familiar stimuli. Together these findings extend work on verbalization to picture recognition and place important parameters on stimulus and task constraints that contribute to contrasting beneficial and detrimental effects of verbalization on recognition memory.

Independent influences of verbalization and race on the configural and featural processing of faces: a behavioral and eye movement study.

Describing a face in words can either hinder or help subsequent face recognition. Here, the authors examined the relationship between the benefit from verbally describing a series of faces and the same-race advantage (SRA) whereby people are better at recognizing unfamiliar faces from their own race as compared with those from other races. Verbalization and the SRA influenced face recognition independently, as evident on both behavioral (Experiment 1) and eye movement measures (Experiment 2). The findings indicate that verbalization and the SRA each recruit different types of configural processing, with verbalization modulating face learning and the SRA modulating both face learning and recognition. Eye movement patterns demonstrated greater feature sampling for describing as compared with not describing faces and for other-race as compared with same-race faces. In both cases, sampling of the eyes, nose, and mouth played a major role in performance. The findings support a single process account whereby verbalization can influence perceptual processing in a flexible and yet fundamental way through shifting one's processing orientation.

A visual and semantic locus to beneficial effects of verbalization on face memory.

We examined the effect of verbally describing a face on face memory as assessed in an old-new recognition task. Verbal facilitation, measured by a difference between verbalization and control conditions, was greater for upright than for inverted faces and greater for unfamiliar than for familiar faces. We propose that generating a verbal description enhances the processing of global visual information that differentiates an individual face from other faces that are encountered and also improves recognition through the association of visually derived semantic information. Verbalization enhances visual and semantic distinctiveness in memory.

Animal recognition and eye movements: the contribution of outline contour and local feature information.

We assessed the importance of outline contour and individual features in mediating the recognition of animals by examining response times and eye movements in an animal-object decision task (i.e., deciding whether or not an object was an animal that may be encountered in real life). There were shorter latencies for animals as compared with nonanimals and performance was similar for shaded line drawings and silhouettes, suggesting that important information for recognition lies in the outline contour. The most salient information in the outline contour was around the head, followed by the lower torso and leg regions. We also observed effects of object orientation and argue that the usefulness of the head and lower torso/leg regions is consistent with a role for the object axis in recognition.

Independent effects of colour on object identification and memory.

We examined the effects of colour on object identification and memory using a study-test priming procedure with a coloured-object decision task at test (i.e., deciding whether an object is correctly coloured). Objects were selected to have a single associated colour and were either correctly or incorrectly coloured. In addition, object shape and colour were either spatially integrated (i.e., colour fell on the object surface) or spatially separated (i.e., colour formed the background to the object). Transforming the colour of an object from study to test (e.g., from a yellow banana to a purple banana) reduced priming of response times, as compared to when the object was untransformed. This utilization of colour information in object memory was not contingent upon colour falling on the object surface or whether the resulting configuration was of a correctly or incorrectly coloured object. In addition, we observed independent effects of colour on response times, whereby coloured-object decisions were more efficient for correctly than for incorrectly coloured objects but only when colour fell on the object surface. These findings provide evidence for two distinct mechanisms of shape-colour binding in object processing.

Sources of error in picture naming under time pressure.

We used a deadline procedure to investigate how time pressure may influence the processes involved in picture naming. The deadline exaggerated errors found under naming without deadline. There were also category differences in performance between living and nonliving things and, in particular, for animals versus fruit and vegetables. The majority of errors were visuallyand semantically related to the target (e. celery-asparagus), and there was a greater proportion of these errors made to living things. Importantly, there were also more visual-semantic errors to animals than to fruit and vegetables. In addition, there were a smaller number of pure semantic errors (e.g., nut-bolt), which were made predominantly to nonliving things. The different kinds of error were correlated with different variables. Overall, visual-semantic errors were associated with visual complexity and visual similarity, whereas pure semantic errors were associated with imageability and age of acquisition. However, for animals, visual-semantic errors were associated with visual complexity, whereas for fruit and vegetables they were associated with visual similarity. We discuss these findings in terms of theories of category-specific semantic impairment and models of picture naming.

Effects of delay on color priming for natural objects.

Using a standard study-test procedure, color priming was examined through effects of color transformation, from correctly colored to incorrectly colored and vice versa, for natural objects with pre-existing color-shape associations, e.g., yellow banana. More specifically these effects were examined at study-test delays of 0, 24, and 48 hr. When deciding whether an object was correctly colored, color transformation eliminated priming. Furthermore, there was evidence that for objects that were not transformed, priming was stronger for correctly as compared with incorrectly colored objects. In addition, the introduction of 24- and 48-hr. delays between the study and the test phase of the task reduced the effects of color transformation on priming. These findings are discussed in terms of the representations that mediate implicit memory performance.

Preserved conceptual priming in Alzheimer's disease.

We assessed Alzheimer's disease (AD) and healthy older adult control (HC) group performance on: (1) a conceptual priming task, in which participants had to make a semantic decision as to whether a degraded picture of an object encountered previously belonged to the category of living or non-living things; and (2) a recognition memory task. The AD group showed a dissociation between impaired performance on the recognition task and preserved priming for semantic decisions to degraded pictures. We argue that it is not whether priming is conceptual or perceptual that is important for the observation of priming in AD, rather it is the nature of the response that is required (c.f., Gabrieli et al., 1999).

Verbal overshadowing of perceptual discrimination.

We examined effects of verbal interference on a perceptual discrimination task. Participants were presented with a series of faces, described (or did not describe) an additional face, and then made face/ nonface decisions to both the original faces and new faces, intermingled with nonfaces. This enabled us to examine the effect of making a verbal description, relative to an unrelated filler task in a control condition, on the perceptual discrimination of faces seen for the first time and faces encountered previously, and also on repetition priming (i.e., the facilitative effect of an encounter with a stimulus on subsequent processing of the same stimulus). Verbalization interfered with performance on both new and studied faces, but it did not interfere with priming. We argue that verbalization encouraged a relatively long-lasting shift (over a number of trials) toward greater visual processing of individual facial features at the expense of more global visual processing, which is generally beneficial for the recognition of faces and important for discriminating faces from nonfaces in the face decision task.

Beneficial effects of verbalization and visual distinctiveness on remembering and knowing faces.

We examined the effect of verbally describing faces upon visual memory. In particular, we examined the locus of the facilitative effects of verbalization by manipulating the visual distinctiveness ofthe to-be-remembered faces and using the remember/know procedure as a measure of recognition performance (i.e., remember vs. know judgments). Participants were exposed to distinctive faces intermixed with typical faces and described (or not, in the control condition) each face following its presentation. Subsequently, the participants discriminated the original faces from distinctive and typical distractors in a yes/no recognition decision and made remember/know judgments. Distinctive faces elicited better discrimination performance than did typical faces. Furthermore, for both typical and distinctive faces, better discrimination performance was obtained in the description than in the control condition. Finally, these effects were evident for both recollection- and familiarity-based recognition decisions. We argue that verbalization and visual distinctiveness independently benefit face recognition, and we discuss these findings in terms of the nature of verbalization and the role of recollective and familiarity-based processes in recognition.

The role of color in the implicit memory performance of healthy older adults and individuals with Alzheimer's disease.

Although the Alzheimer's disease (AD) patients in this study were severely impaired in recognition performance, their naming performance demonstrated normal priming across transformations in object color. This is evidence for preserved implicit shape-based memory performance in AD patients. For colored-object decision, healthy older adult control participants but not AD patients showed priming for new associations between previously encountered object shapes and colors. The author argues, on the basis of this colored object decision performance, that the deficits present in AD do not allow shape and color to be integrated to form a novel unitized representation that can be used to benefit cognitive performance.

Verbal facilitation of face recognition.

We examined the effects of verbally describing a face on face memory, as assessed in an old/new recognition task. Experiment 1 established that describing faces facilitated their later recognition. In Experiment 2, we argue that verbalization facilitated the recognition of faces that had been previously described, but not of faces intermingled with the described faces. In Experiment 3, the participants described (or did not, in the control condition) either differences or similarities between pairs of faces. Verbal facilitation was equivalent for both types of descriptions. Finally, in Experiment 4, the participants were instructed to generate either holistic or featural descriptors. Verbal facilitation was equivalent for both types of descriptors. We discuss these findings in terms of the nature of the verbalization that benefits face recognition.

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.

The role of colour in implicit and explicit memory performance.

We present two experiments that examine the effects of colour transformation between study and test (from black and white to colour and vice versa, of from incorrectly coloured to correctly coloured and vice versa) on implicit and explicit measures of memory for diagnostically coloured natural objects (e.g., yellow banana). For naming and coloured-object decision (i.e., deciding whether an object is correctly coloured), there were shorter response times to correctly coloured-objects than to black-and-white and incorrectly coloured-objects. Repetition priming was equivalent for the different stimulus types. Colour transformation did not influence priming of picture naming, but for coloured-object decision priming was evident only for objects remaining the same from study to test. This was the case for both naming and coloured-object decision as study tasks. When participants were asked to consciously recognize objects that they had named or made coloured-object decisions to previously, whilst ignoring their colour, colour transformation reduced recognition efficiency. We discuss these results in terms of the flexibility of object representations that mediate priming and recognition.

Outline shape is a mediator of object recognition that is particularly important for living things.

We assess the importance of outline shape in mediating the recognition of living and nonliving things. Natural objects were presented as shaded line drawings or silhouettes, and were living and nonliving things. For object decision (deciding whether an object may be encountered in real life) there were longer response times to nonliving than to living things. Importantly, this category difference was greater for silhouettes than for shaded line drawings. For naming, similar category and stimulus differences were evident, but were not as pronounced. We also examined effects of prior naming on subsequent object decision performance. Repetition priming was equivalent for nonliving and living things. However, prior presentation of silhouettes (but not shaded line drawings) reduced the longer RT to nonliving things relative to living things in silhouette object decision. We propose that outline contour benefits recognition of living things more than nonliving things: For nonliving things, there may be greater 2-D/3-D interpretational ambiguity, and/or they may possess fewer salient features.

Effects of plane rotation, task, and complexity on recognition of familiar and chimeric objects.

We examined the effects of plane rotation, task, and visual complexity on the recognition of familiar and chimeric objects. The effects of rotation, with response times increasing linearly and monotonically with rotation from the upright, were equivalent for tasks requiring different degrees of visual differentiation of the target from contrasting stimuli--namely, (1) deciding whether the stimulus was living or nonliving (semantic classification), (2) deciding whether the stimulus was an object or a nonobject (object decision), and (3) naming. The effects of complexity, with shorter response times to more complex stimuli, were most apparent in semantic classification and object decision and were additive with the effects of rotation. We discuss the implications of these results for theories of the relationship between the process of normalization and the determining of object identity.