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A vector-based model of discriminative learning is presented. It is demonstrated to learn association strengths identical to the Rescorla-Wagner model under certain parameter settings (Rescorla & Wagner, 1972, Classical Conditioning II: Current Research and Theory, 2, 64-99). For other parameter settings, it approximates the association strengths learned by the Rescorla-Wagner model. I argue that the Rescorla-Wagner model has conceptual details that exclude it as an algorithmically plausible model of learning. The vector learning model, however, does not suffer from the same conceptual issues. Finally, we demonstrate that the vector learning model provides insight into how animals might learn the semantics of stimuli rather than just their associations. Results for simulations of language processing experiments are reported.

Analogical transfer is the ability to transfer knowledge despite significant changes in the surface features of a problem. In categorization, analogical transfer occurs if a classification strategy learned with one set of stimuli can be transferred to a set of novel, perceptually distinct stimuli. Three experiments investigated analogical transfer in rule-based and information-integration categorization tasks. In rule-based tasks, the optimal strategy is easy to describe verbally, whereas in information-integration tasks, accuracy is maximized only if information from two or more stimulus dimensions is integrated in a way that is difficult or impossible to describe verbally. In all three experiments, analogical transfer was nearly perfect in the rule-based conditions, but no evidence for analogical transfer was found in the information-integration conditions. These results were predicted a priori by the COVIS theory of categorization.

Distractor inhibition and distractor-response binding were investigated in two experiments by analyzing distractor repetition benefits and their interaction with response repetition effects in a sequential-priming paradigm. Distractor repetition benefits were larger for distractors that were incompatible with the to-be-executed response (task-related distractors) than for distractors that were not assigned to a response (neutral distractors), indicating that the strength of distractor inhibition was a function of response interference for the distractors. In contrast, the distractor-response bindings were found to be of equal strength for both task-related and neutral distractors. Thus, differences in the strengths of distractor inhibition did not affect the integration of distractors with responses into event files. Instead, our results suggest that distractor-response binding and distractor inhibition are independent mechanisms that are recruited for the automatization of behavior and action control.

Studies of implicit memory for novel associations have focused primarily on verbal materials and have highlighted the contribution of conceptually unitized representations to such priming. Using pictorial stimuli in a perceptual identification task, we examined whether new association priming can occur at a purely perceptual level. By manipulating the spatial contiguity of stimuli, we also evaluated whether such priming requires the creation of perceptually unitized representations. Finally, we examined the status of such priming in aging. In Experiment 1, we found that spatial contiguity of stimuli is not necessary for novel pictorial association priming to emerge, although such contiguity does enhance the magnitude of associative priming. In Experiment 2, we found that new association priming is age invariant, regardless of spatial contiguity. In Experiment 3, we provide additional evidence that pictorial association priming is perceptually based. These findings expand the scope and delineate the conditions of novel association priming and inform theories about the nature of implicit memory for new associations.

Categories are learned and used in a variety of ways, but the research focus has been on classification learning. Recent work contrasting classification with inference learning of categories found important later differences in category performance. However, theoretical accounts differ on whether this is due to an inherent difference between the tasks or to the implementation decisions. The inherent-difference explanation argues that inference learners focus on the internal structure of the categories--what each category is like--while classification learners focus on diagnostic information to predict category membership. In two experiments, using real-world categories and controlling for earlier methodological differences, inference learners learned more about what each category was like than did classification learners, as evidenced by higher performance on a novel classification test. These results suggest that there is an inherent difference between learning new categories by classifying an item versus inferring a feature.

In two experiments, we examined spacing effects on the learning of bird families and metacognitive assessments of such learning. Results revealed that spacing enhanced learning beyond massed study. These effects were increased by presenting birds in pairs so as to highlight differences among families during study (Experiment 1). Self-allocated study time provided evidence that more attention was paid during spaced than during massed study and resulted in no age differences in learning (Experiment 2). Metacognitive measures revealed sensitivity to the processing advantage of spaced study and to differences in classification difficulty across categories. No difference occurred in monitoring accuracy for young versus older adults. These findings provide evidence for discrimination- and attention-based accounts of the spacing effect in natural concept learning.

Many current computational models of object categorization either include no explicit provisions for dealing with incomplete stimulus information (e.g. Kruschke, Psychological Review 99:22-44, 1992) or take approaches that are at odds with evidence from other fields (e.g. Verguts, Ameel, & Storms, Memory & Cognition 32:379-389, 2004). In two experiments centered around the inverse base-rate effect, we demonstrate that people not only make highly informed inferences about the values of unknown features, but also subsequently use the inferred values to come to a categorization decision. The inferences appear to be based on immediately available information about the particular stimulus under consideration, as well as on higher-level inferences about the stimulus class as a whole. Implications for future modeling efforts are discussed.

In visual change detection tasks, providing a cue to the change location concurrent with the test image (post-cue) can improve performance, suggesting that, without a cue, not all encoded representations are automatically accessed. Our studies examined the possibility that post-cues can encourage the retrieval of representations stored in long-term memory (LTM). Participants detected changes in images composed of familiar objects. Performance was better when the cue directed attention to the post-change object. Supporting the role of LTM in the cue effect, the effect was similar regardless of whether the cue was presented during the inter-stimulus interval, concurrent with the onset of the test image, or after the onset of the test image. Furthermore, the post-cue effect and LTM performance were similarly influenced by encoding time. These findings demonstrate that monitoring the visual world for changes does not automatically engage LTM retrieval.

In four experiments, we investigated how people make feature predictions about objects whose category membership is uncertain. Artificial visual categories were presented and remained in view while a novel instance with a known feature, but uncertain category membership was presented. All four experiments showed that feature predictions about the test instance were most often based on feature correlations (referred to as feature conjunction reasoning). Experiment 1 showed that feature conjunction reasoning was generally preferred to category-based induction in a feature prediction task. Experiment 2 showed that people used all available exemplars to make feature conjunction predictions. Experiments 3 and 4 showed that the preference for predictions based on feature conjunction persisted even when category-level information was made more salient and inferences involving a larger number of categories were required. Little evidence of reasoning based on the consideration of multiple categories (e.g., Anderson, (Psychological Review, 98:409-429, 1991)) or the single, most probable category (e.g., Murphy & Ross, (Cognitive Psychology, 27:148-193, 1994)) was found.

Three experiments used a change detection paradigm across a range of study-test intervals to address the respective contributions of location, shape, and color to the formation of bindings of features in sensory memory and visual short-term memory (VSTM). In Experiment 1, location was designated task irrelevant and was randomized between study and test displays. The task was to detect changes in the bindings between shape and color. In Experiments 2 and 3, shape and color, respectively, were task irrelevant and randomized, with bindings tested between location and color (Experiment 2) and location and shape (Experiment 3). At shorter study-test intervals, randomizing location was most disruptive, followed by shape and then color. At longer intervals, randomizing any task-irrelevant feature had no impact on change detection for bindings between features, and location had no special role. Results suggest that location is crucial for initial perceptual binding but loses that special status once representations are formed in VSTM, which operates according to different principles, than do visual attention and perception.

Verbal information is coded naturally as ordered representations in working memory (WM). However, this may not be true for spatial information. Accordingly, we used memory span tasks to test the hypothesis that serial order is more readily bound to verbal than to spatial representations. Removing serial-order requirements improved performance more for spatial locations than for digits. Furthermore, serial order was freely reproduced twice as frequently for digits as for locations. When participants reordered spatial sequences, they minimized the mean distance between items. Participants also failed to detect changes in serial order more frequently for spatial than for verbal sequences. These results provide converging evidence for a dissociation in the binding of serial order to spatial versus verbal representations. There may be separable domain-specific control processes responsible for this binding. Alternatively, there may be fundamental differences in how effectively temporal information can be bound to different types of stimulus features in WM.

Spatial judgments are affected by both fine-grained and categorical knowledge. We investigated whether, and how, the two forms of knowledge are learned in real-world, navigable space, as well as the time course of learning each type of knowledge. Participants were Northwestern University undergraduates who estimated the locations of buildings and other landmarks on campus. The Northwestern campus is roughly divided into three regions whose borders are not easy to discern, either from a map or by navigation. Nevertheless, students often refer to these regions linguistically and use them when making housing decisions, choosing classes, and so forth. We found that knowledge of both the fine-grained configuration of locations and the regional distinctions increased with time. However, regional influences on judgments occurred later in students' time on campus. Consequently, computed distances across the nonexistent border between north and south campus locations became more biased with time. The results have implications for understanding how spatial representations develop in navigable environments.

We examined two forms of top-down effects on visual selection: (1) information held in working memory (WM) and (2) the semantic relations between targets and distractors. We found that items held in WM affected search for a different target. This WM-based interference effect generalized across different exemplars, even though participants could remember the specific exemplar on the trial. This argues against a memory top-up account of performance. In addition, there was interference from distractors that were not held in WM but were semantically related to the target. The effects of WM capture and the effects of capture by a distractor related to the target combined additively. The data suggest that task-irrelevant information in WM and task-relevant templates for targets compete separately for selection. The implications for understanding top-down processes in search are discussed.

Can the visual system extrapolate spatial layout of a scene to new viewpoints after a single view? In the present study, we examined this question by investigating the priming of spatial layout across depth rotations of the same scene (Sanocki & Epstein, 1997). Participants had to indicate which of two dots superimposed on objects in the target scene appeared closer to them in space. There was as much priming from a prime with a viewpoint that was 10° different from the test image as from a prime that was identical to the target; however, there was no reliable priming from larger differences in viewpoint. These results suggest that a scene's spatial layout can be extrapolated, but only to a limited extent.

State-trace analysis was used to investigate the effect of concurrent working memory load on perceptual category learning. Initial reanalysis of Zeithamova and Maddox (2006, Experiment 1) revealed an apparently two-dimensional state-trace plot consistent with a dual-system interpretation of category learning. However, three modified replications of the original experiment found evidence of a single resource underlying the learning of both rule-based and information integration category structures. Follow-up analyses of the Zeithamova and Maddox data, restricted to only those participants who had learned the category task and performed the concurrent working memory task adequately, revealed a one-dimensional plot consistent with a single-resource interpretation and the results of the three new experiments. The results highlight the potential of state-trace analysis in furthering our understanding of the mechanisms underlying category learning.

Rotated mirror/normal letter discriminations are thought to require mental rotation in order to determine the direction of facing of the stimulus. The response time (RT) function over orientation tends to be curved, rather than the linear function found for other mental rotation tasks. The present study investigated the possibility that the curved RT function is a result of a mixture of trials requiring and not requiring mental rotation. The results suggested that the frequency of mental rotation is also a linear function of stimulus orientation. Moreover, the relationship between an individual's rate of plane rotation and the mean difference in RT between mirror and normal stimuli was replicated, supporting the suggestion that mirrored stimuli are flipped after they are spun (Hamm, Johnson, & Corballis, 2004). On the basis of the present findings, the entire RT function can be modeled by using only the mean RTs for upright and inverted stimuli.

Several studies have shown that recall performance depends on the extent to which an item differs from other items in a sequence (the distinctiveness effect; see, e.g., Kelley & Nairne, 2001). Distinctiveness effects, however, have been demonstrated mainly in the verbal domain. The present study extends distinctiveness effects to the spatial domain. In two experiments, participants recalled the order in which series of spatially located dots had been presented. Item discriminability was varied within the sequence by manipulating the duration of the interval inserted between the presentation of the dots (Experiment 1) and the perceptual characteristics of the stimuli (Experiment 2). The results showed that these manipulations in the spatial domain produce distinctiveness effects similar to those observed with verbal material (see, e.g., Neath & Crowder, 1990) and suggest that distinctiveness models of memory should take into account the processing of spatial information.

Selective attention protects cognition against intrusions of task-irrelevant stimulus attributes. This protective function was tested in coordinated psychophysical and memory experiments. Stimuli were superimposed, horizontally and vertically oriented gratings of varying spatial frequency; only one orientation was task relevant. Experiment 1 demonstrated that a task-irrelevant spatial frequency interfered with visual discrimination of the task-relevant spatial frequency. Experiment 2 adopted a two-item Sternberg task, using stimuli that had been scaled to neutralize interference at the level of vision. Despite being visually neutralized, the task-irrelevant attribute strongly influenced recognition accuracy and associated reaction times (RTs). This effect was sharply tuned, with the task-irrelevant spatial frequency having an impact only when the task-relevant spatial frequencies of the probe and study items were highly similar to one another. Model-based analyses of judgment accuracy and RT distributional properties converged on the point that the irrelevant orientation operates at an early stage in memory processing, not at a later one that supports decision making.

In order to determine whether people encode spatial configuration information when encoding visual displays, in four experiments, we investigated whether changes in task-irrelevant spatial configuration information would influence color change detection accuracy. In a change detection task, when objects in the test display were presented in new random locations, rather than identical or different locations preserving the overall configuration, participants were more likely to report that the colors had changed. This consistent bias across four experiments suggested that people encode task-irrelevant spatial configuration along with object information. Experiment 4 also demonstrated that only a low-false-alarm group of participants effectively bound spatial configuration information to object information, suggesting that these types of binding processes are open to strategic influences.

Two experiments measured the joint influence of three key sets of semantic features on the frequency with which artifacts (Experiment 1) or plants and creatures (Experiment 2) were categorized in familiar categories. For artifacts, current function outweighed both originally intended function and current appearance. For biological kinds, appearance and behavior, an inner biological function, and appearance and behavior of offspring all had similarly strong effects on categorization. The data were analyzed to determine whether an independent cue model or an interactive model best accounted for how the effects of the three feature sets combined. Feature integration was found to be additive for artifacts but interactive for biological kinds. In keeping with this, membership in contrasting artifact categories tended to be superadditive, indicating overlapping categories, whereas for biological kinds, it was subadditive, indicating conceptual gaps between categories. It is argued that the results underline a key domain difference between artifact and biological concepts.

In two experiments, we investigated the activation of perceptual representations of referent objects during word processing. In both experiments, participants learned to associate pictures of novel three-dimensional objects with pseudowords. They subsequently performed a recognition task (Experiment 1) or a naming task (Experiment 2) on the object names while being primed with different types of visual stimuli. Only the stimuli that the participants had encountered as referent objects during the training phase facilitated recognition or naming responses. New stimuli did not facilitate the processing of object names, even if they matched a schematic or prototypical representation of the referent object that the participants might have abstracted during word-referent learning. These results suggest that words learned by way of examples of referent objects are associated with experiential traces of encounters with these objects.

When one is sequentially switching among three tasks, performance is impaired when tasks alternate (ABA) relative to when one is switching between all three tasks (CBA), an effect known as backward inhibition (BI). BI is not observed when component tasks are uniquely located in space, however (Arbuthnott, 2005). In this study, the locations of task precues and target stimuli were manipulated independently to determine whether this elimination of BI is related to distinct cue location or to distinct target location. Results clearly indicated that BI is eliminated with distinct cue localization independent of the location of target stimuli. This indicates that BI, which reflects suppression of task-set representations, can be influenced by cue characteristics that are associated with task representations.

Category learning theorists tacitly assume that stimuli are encoded by a single pathway. Motivated by theories of object recognition, we evaluated a dual-pathway account of stimulus encoding. The part-based pathway establishes mappings between sensory input and symbols that encode discrete stimulus features, whereas the image-based pathway applies holistic templates to sensory input. Our experiments used rule-plus-exception structures, in which one exception item in each category violates a salient regularity and must be distinguished from other items. In Experiment 1, we found discrete representations to be crucial for recognition of exceptions following brief training. Experiments 2 and 3 involved multisession training regimens designed to encourage either part- or image-based encoding. We found that both pathways are able to support exception encoding, but have unique characteristics. We speculate that one advantage of the part-based pathway is the ability to generalize across domains, whereas the image-based pathway provides faster and more effortless recognition.

Do all components of a sign contribute equally to its recognition? In the present study, misperceptions in the sign-spotting task (based on the word-spotting task; Cutler & Norris, 1988) were analyzed to address this question. Three groups of deaf signers of British Sign Language (BSL) with different ages of acquisition (AoA) saw BSL signs combined with nonsense signs, along with combinations of two nonsense signs. They were asked to spot real signs and report what they had spotted. We will present an analysis of false alarms to the nonsense-sign combinations-that is, misperceptions of nonsense signs as real signs (cf. van Ooijen, 1996). Participants modified the movement and handshape parameters more than the location parameter. Within this pattern, however, there were differences as a function of AoA. These results show that the theoretical distinctions between form-based parameters in sign-language models have consequences for online processing. Vowels and consonants have different roles in speech recognition; similarly, it appears that movement, handshape, and location parameters contribute differentially to sign recognition.

In three experiments, we explored the basis of adults' judgments of individual object persistence through transformation. Participants watched scenarios in which an object underwent a transformation into an object belonging to the same or a different basic-level kind. Participants were queried about the object's persistence through the transformation as an individual (indexed by its proper name) and as a member of the original kind (indexed by its basic-level count noun in Experiments 1 and 2, or by its superordinate-level noun in Experiment 3). In all experiments, participants rated objects that were altered in a way that maintained basic-level kind to be less likely to retain their proper name than those that were altered in a way that changed basic-level kind. These findings suggest that shared basic-level kind membership serves as a dimension of similarity over which objects' unique individual identities are highlighted. We discuss the implications of the results for existing theoretical accounts of adults' judgments of individual object persistence.

In the possible/impossible object decision test, priming has consistently been found for structurally possible, but not impossible, objects, leading Schacter, Cooper, and Delaney (1990) to suggest that priming relies on a system that represents the global 3-D structure of objects. Using a modified design with matching objects to control for the influence of episodic memory, Ratcliff and McKoon (1995) and Williams and Tarr (1997) found negative priming for impossible objects (i.e., lower performance for old than for new items). Both teams argued that priming derives from (1) episodic memory for object features and (2) bias to respond "possible" to encoded objects or their possible parts. The present study applied the matched-objects design to the original Schacter and Cooper stimuli-same possible objects and matching impossible figures-with minimal procedural variation. The data from Experiment 1 only partially supported the bias models and suggested that priming was mediated by both local and global structural descriptions. Experiment 2 showed that negative priming for impossible objects derived from the structural properties of these objects, not from the influence of episodic memory on task performance. Supplemental materials for this study may be downloaded from mc.psychonomic-journals.org/content/supplemental.

A critical function of categories is their use in property inference (Heit, 2000). However, one challenge to using categories in inference is that most entities in the world belong to multiple categories (e.g., Fido could be a dog, a pet, a mammal, or a security system). Building on Patalano, Chin-Parker, and Ross (2006), we tested the hypothesis that category coherence (the extent to which category features go together in light of prior knowledge) influences the selection of categories for use in property inference about cross-classified entities. In two experiments, we directly contrasted coherent and incoherent categories, both of which included cross-classified entities as members, and we found that the coherent categories were used more readily as the source of both property transfer and property extension. We conclude that category coherence, which has been found to be a potent influence on strength of inference for singly classified entities (Rehder & Hastie, 2004), is also central to category use in reasoning about novel cross-classified ones.

In two experiments, participants were trained to recognize a playground scene from four vantage points and were subsequently asked to recognize the playground from a novel perspective between the four learned viewing perspectives, as well as from the trained perspectives. In both experiments, people recognized the novel view more efficiently than those that they had recently used in order to learn the scene. Additionally, in Experiment 2, participants who viewed a novel stimulus on their very first test trial correctly recognized it more quickly (and also tended to recognize it more accurately) than did participants whose first test trial was a familiar view of the scene. These findings call into question the idea that scenes are recognized by comparing them with single previous experiences, and support a growing body of literature on the existence of psychological mechanisms that combine spatial information from multiple views of a scene.

How does the causal structure of a problem concept influence judgments of treatment efficacy? We argue that the task of evaluating treatment efficacy involves a combination of causal reasoning and categorization. After an exemplar has been categorized, a treatment task involves judging where to intervene in the causal structure to eradicate the problem, removing the exemplar from category membership. We hypothesized that the processes underlying such category membership removal tasks are not identical to those underlying categorization. Whereas previous experiments have shown that both the root cause (as the most generative feature) and the coherence of the exemplar heavily influence categorization, Experiments 1 and 2 showed that people base category membership removal judgments on the root cause. In Experiment 3, people spontaneously chose to remove an exemplar from category membership when asked to treat the terminal effect. We discuss how our findings are compatible with existing models of categorization. A description of pilot studies for Experiment 1 may be downloaded as supplemental materials from mc.psychonomic-journals.org.

Schneider and Shiffrin (1977) proposed that training under consistent stimulus-response mapping (CM) leads to automatic target detection in search tasks. Other theories, such as Treisman and Gelade's (1980) feature integration theory, consider target-distractor discriminability as the main determinant of search performance. The first two experiments pit these two principles against each other. The results show that CM training is neither necessary nor sufficient to achieve optimal search performance. Two other experiments examine whether CM trained targets, presented as distractors in unattended display locations, attract attention away from current targets. The results are again found to vary with target-distractor similarity. Overall, the present study strongly suggests that CM training does not invariably lead to automatic attention attraction in search tasks.

When we look around within a visual scene, is visual information automatically placed in visual memory during each saccade, or can we control which information is retained and which is excluded? We examined this question in five experiments by requiring participants to remember sequentially presented visual shapes or faces-some of which were marked for encoding (targets) and others that were supposed to be ignored (distractors)-over a 1-sec delay. The results show that distractors were retained in visual memory, regardless of stimulus category, suggesting that it is a general phenomenon. Whether or not participants were allowed to prepare for a target or distractor did not modulate distractor intrusion. When attention coupled with eye movements could be used to select targets, distractors were no longer encoded into memory. When eye movements were constrained, distractors once again intruded into memory. These findings suggest that top-down control processes are insufficient to filter the contents of visual memory.

Compatibility effects in conflict paradigms are reduced following incompatible trials, and this effect is referred to as conflict adaptation. A perplexing pattern exists, however, with conflict-driven adaptation emerging in several paradigms (e.g., Stroop, Simon) but not consistently in the Eriksen and Eriksen (1974) flanker task. The present experiments address the seemingly elusive presence of conflict adaptation in this task. Experiment 1 shows that a negative-priming-like slowing may be masking conflict adaptation in the flanker task. In Experiment 2, conflict adaptation was revealed when a larger stimulus set designed to reduce negative priming was implemented. Taken together, the findings indicate that a consideration of processes opposing conflict adaptation in the flanker task may help reconcile prior findings.

The picture superiority effect has been well documented in tests of item recognition and recall. The present study shows that the picture superiority effect extends to associative recognition. In three experiments, students studied lists consisting of random pairs of concrete words and pairs of line drawings; then they discriminated between intact (old) and rearranged (new) pairs of words and pictures at test. The discrimination advantage for pictures over words was seen in a greater hit rate for intact picture pairs, but there was no difference in the false alarm rates for the two types of stimuli. That is, there was no mirror effect. The same pattern of results was found when the test pairs consisted of the verbal labels of the pictures shown at study (Experiment 4), indicating that the hit rate advantage for picture pairs represents an encoding benefit. The results have implications for theories of the picture superiority effect and models of associative recognition.

Task switching research has revealed that task changes lead to a performance switch cost. The present study focuses on the organization of task components in the task set. Three different views of task set organization have been distinguished and evidence in favor of each of these has been reported in the literature. In four experiments, we orthogonally varied the categorization task (magnitude and parity) and the stimulus dimension on which the categorization was to be made. Experiments 1, 2, and 4 used Stroop-like number stimuli, whereas Experiment 3 used global-local stimuli to define the stimulus dimension. In Experiments 2-4, the cue-stimulus interval was also varied. The findings showed that a change of any component resulted in a cost, without any reliable difference in the size of these costs. These results are consistent with the flat view on task-set organization, which assumes that the task set binds all elements in an unstructured representation, which is completely reconfigured each time a change to the task set is required. The implications of these findings are discussed in relation to other findings and the different views on task-set organization.

Withholding an action plan in memory for later execution can delay execution of another action if the actions share a similar (compatible) action feature (e.g., response hand). We investigated whether this phenomenon, termed compatibility interference (CI), occurs for responses associated with a target as well as responses associated with distractors in a visual selection task. Participants planned and withheld a sequence of keypress responses (with their right or left hand), according to the identity of a stimulus (A), and then immediately executed a keypress response (with their right or left hand) to a second stimulus (B), according to the identity of a target letter appearing alone or among distractor letters. Distractor letters were either response compatible or incompatible with the target and appeared either simultaneously with the target (Experiments 1A and 2) or 100 msec before the target (Experiment 1B). Also, stimulus-response mapping was either 1:1 (Experiment 1) or 2:1 (Experiment 2). Results showed that the response to the Stimulus B target was delayed when it required the same response hand as Stimulus A, as opposed to a different hand. Also, the target reaction time for Stimulus B was greater when the target was flanked by incompatible distractors than when it was flanked by compatible distractors. Moreover, the degree of CI was consistent across the compatible-, incompatible-, and no-distractor conditions, indicating that CI generalizes to responses associated with a target, but not to those associated with distractors. Thus, CI occurs at a response selection, not at a response activation stage. Implications for the code occupation account for CI (e.g., Stoet & Hommel, 1999, 2002) and an alternative account for CI are discussed.

Traditional associative models assume that associative weights are updated on a trial-by-trial basis. As a result, it is usually expected that responses based on these weights will tend to reflect the most recently presented contingencies. However, a number of studies of human causal judgments have shown primacy effects, wherein judgments obtained at the end of a series of trials are more strongly influenced by a contingency that was in force early in the sequence than by a contingency that was in force later in the sequence. The experiments described in this article replicated other work showing that requesting causal judgments during a sequence can reverse primacy and produce strong recency effects. Evidence was also obtained to suggest that primacy effects are produced by an interaction between latent inhibition and extinction processes and that requesting a judgment affects both of these processes.

In three studies, we examined simple counterexample-based and probabilistic reasoning in children 6, 7, and 9 years of age. In the first study, participants were asked to make conditional (if-then) inferences under both categorical (certain or uncertain) and probabilistic instructions. Results showed that 6-year-olds respond to both forms of inference in similar ways, but whereas probabilistic conditional inferences showed little development over this period, categorical inferences clearly improved between 6 and 7 years of age. An analysis of the children's justifications indicated that performance under categorical instructions was strongly related to counterexample generation at all ages, whereas this was true only for the younger children for inferences under probabilistic instructions. These findings were replicated in a second study, using problems that referred to concrete stimuli with varying probabilities of inference. A third study tested the hypothesis that children confused probability judgments with judgments of confidence and demonstrated a clear dissociation between these two constructs. Overall, these results show that children are capable of accurate conditional inferences under probabilistic instructions at a very early age and that the differentiation between categorical and probabilistic conditional reasoning is clear by at least 9 years ofage. These results are globally consistent with dual-process theories but suggest some difficulties for the way that the analytic-heuristic distinction underlying these theories has been conceptualized.

In transitive inference, participants learn a set of context-dependent discriminations that can be organized into a hierarchy that supports inference. Several studies show that inference occurs with or without task awareness. However, some studies assert that without awareness, performance is attributable to pseudoinference. By this account, inference-like performance is achieved by differential stimulus weighting according to the stimuli's proximity to the end items of the hierarchy. We implement an inference task that cannot be based on differential stimulus weighting. The design itself rules out pseudoinference strategies. Success on the task without evidence of deliberative strategies would therefore suggest that true inference can be achieved implicitly. We found that accurate performance on the inference task was not dependent on explicit awareness. The finding is consistent with a growing body of evidence that indicates that forms of learning and memory supporting inference and flexibility do not necessarily depend on task awareness.

Previous research has shown that visual search performance is modulated by the current contents in visual working memory (VWM), even when the contents of VWM are irrelevant to the search task. For example, visual search is faster when the target--rather than a distractor--is surrounded by a shape currently held in VWM. This study uses the modulation of visual search by VWM to investigate properties of VWM. Participants wereasked to remember the color or the shape of novel polygons whose "goodness" of figure varied according to Garner's (1962) rotation and reflection transformation principle. During the memory retention interval, participants searched for a tilted line among vertical lines embedded inside colored polygons. Search was faster when the target--rather than a distractor--was enclosed by the remembered polygons. The congruity effect diminished with increasing memory load and decreasing figure goodness. We conclude that congruity effects in visual search can indirectly assess VWM representation strength.

Using synthetic faces that varied along four perceptual dimensions (Wilson, Loffler, & Wilkinson, 2002), we examined the effects of face similarity on memory for face-name associations. The nature of these stimuli allowed us to go beyond the categorical similarity manipulations used in previous verbal associative memory studies to trace out the parametric relation between similarity and various performance measures. In Experiment 1, we found that recall performance diminished as a function of how many studied faces were in the vicinity of the cue face in similarity space. Also, incorrect recalls were more likely to come from nearby positions in face space. Experiments 2 and 3, respectively, demonstrated analogous effects with a set of more distinguishable, photorealistic faces, and in an associative recognition task. These results highlight the similarity between associative recall and associative recognition, and between face-name association and other domains of associative memory.

Two basic approaches to explaining the nature of the mind are the rational and the mechanistic approaches. Rational analyses attempt to characterize the environment and the behavioral outcomes that humans seek to optimize, whereas mechanistic models attempt to simulate human behavior using processes and representations analogous to those used by humans. We compared these approaches with regard to their accounts of how humans learn the variability of categories. The mechanistic model departs in subtle ways from rational principles. In particular, the mechanistic model incrementally updates its estimates of category means and variances through error-driven learning, based on discrepancies between new category members and the current representation of each category. The model yields a prediction, which we verify, regarding the effects of order manipulations that the rational approach does not anticipate. Although both rational and mechanistic models can successfully postdict known findings, we suggest that psychological advances are driven primarily by consideration of process and representation and that rational accounts trail these breakthroughs.

A common way to describe the location of an object is to spatially relate it to a nearby object. For such descriptions, the object being described is referred to as the located object; the object to which it is spatially related is referred to as the reference object. Typically, however, there are many nearby objects (distractors), resulting in the need for selection. We report three experiments that examine the extent to which a distractor in the display is processed during the selection of a reference object. Using acceptability ratings and production measures, we show that the presence and the placement ofa distractor have a significant impact on the assessment of the spatial relation between the located and reference objects; there is also evidence that the properties of the distractor are processed, but only under limited conditions. One implication is that the dimension that is most relevant to reference object selection is its spatial relation to the located object, rather than its salience with respect to other objects in the display.

Verbal overshadowing refers to the surprising effect whereby additional verbal information about a visual stimulus hinders its subsequent recognition. In two experiments, we analyzed the validity of this effect for event recognition across various conditions of presentation and testing. Participants observed events that were either followed (Experiment 1) or preceded (Experiment 2) by a verbal description. Results showed that verbal overshadowing occurred when the verbal description was presented after the visual presentation, independent of the distractor type. However, when the verbal description preceded the event, recognition performance was seen to improve when distractor items incompatible with the verbal description were used. The findings were interpreted in terms of two interacting mental representations, which differ both in their level of abstraction and in their accessibility.

In two experiments, we examined the effects of Stroop interference on the categorical perception (CP; better cross-category than within-category discrimination) of color. Using a successive two-alternative forced choice recognition paradigm (deciding which of two stimuli was identical to a previously presented target), which combined to-be-remembered colors with congruent and incongruent Stroop words, we found that congruent color words facilitated CP, whereas incongruent color words reduced CP. However, this was the case only when Stroop interference was presented together with the target color, but not when Stroop stimuli were introduced at the test stage. This suggests that target name, but not test name generation, affects CP. Target name generation may be important for CP because it acts as a category prime, which, in turn, facilitates cross-category discrimination.

The term contextual cuing refers to improved visual search performance with repeated exposure to a configuration of objects. Participants use predictive cues-derived from learned associations between target locations and the spatial arrangement of the surrounding distractors in a configuration--to efficiently guide search behavior. Researchers have claimed that contextual cuing can occur implicitly. The present experiments examined two explicit measures--generation and recognition. In Experiment 1, we found that contextual cuing information was consciously retrievable when the number of trials used in a generation test was increased, and the results also suggested that the shorter tests that were used previously were not statistically powerful enough to detect a true awareness effect. In Experiment 2, concurrent implicit and explicit (generation and recognition) tests were employed. At a group level, learning did not precede awareness. Although contextual cuing was evident in participants who were selected post hoc as having no explicit awareness, and for specific configurations that did not support awareness, we argue that awareness may nevertheless be a necessary concomitant of contextual cuing. These results demonstrate that contextual cuing knowledge is accessible to awareness.

In three experiments, we examined connections between item-recognition memory and memory for item-position information. With sequences of compound gratings as study and probe items, subjects made either item-position judgments (Experiments 1 and 2), by identifying the serial position of the study item that matched the probe, or recognition judgments (Experiment 3), by judging whether the probe had or had not been presented in the study series. Integrating a summed-similarity account of recognition into a signal detection framework shows that the variance of summed similarities on lure trials (probe not present in the study series) exceeds the variance on target trials (probe present in the study series). This prediction is borne out by the empirical zROC functions, all of which had slopes that were greater than 1. Additionally, about 25% of correct recognitions were accompanied by incorrect item position identification. Misidentifications of item position arose from two sources--structural similarity and positional similarity-which combined in an approximately additive fashion.

Mental rotation of objects improves when passive tactile information for the rotating object accompanies the imagined rotation (Wraga, Creem, & Proffitt, 2000). We examined this phenomenon further using a within-subjects paradigm involving handheld objects. In Experiment 1, participants imagined rotating an unseen object placed on their upturned palms. The participants were faster at mental rotation when the object was rotated on their palm than when the object remained stationary. Experiment 2 tested whether the performance advantage would endure when the participants received tactile information for only the start- and endpoints of the rotation event. This manipulation did not improve performance, relative to a stationary control. Experiment 3 revealed that ambiguous tactile information, continuous with the rotation event but independent of object shape, actually degraded performance, relative to a stationary control. In Experiment 4, we found that continuous tactile rotation discrepant from imagined object movement also hindered performance, as compared with continuous tactile information aligned with imagined object movement. The findings suggest a tight coupling between tactile information specifying continuous object rotation and the corresponding internal representation of the rotating object.

Selective "blindness" to repeated words in rapid serial visual presentation (RSVP) occurs even when omitting these words compromises sentence syntax and meaning. The contributions of lexical and contextual factors to this repetition blindness (RB) phenomenon were evaluated using three tasks that combined RB and ambiguity resolution paradigms. During an RSVP sentence, a repeated word and matched but incongruous control were presented simultaneously, and participants were asked to report the entire sentence, including only the appropriate word. Substantial RB was evident in impaired report of repeated targets, whereas report of nonrepeated targets was enhanced when the distractor was a repeat. Experiment 2 confirmed these results with reduced reporting requirements, and Experiment 3 demonstrated the independence of repetition and sentence congruity effects. Results across all contexts support a lexical account of RB, which assumes that reactivation and identification of rapidly repeated words are impaired due to the refractory nature of lexical representations.

This article assesses whether the two-alternative forced-choice (2AFC) and the reminder tasks (i.e., method of constant stimuli) yield identical estimates of the difference limen (DL). In a series of six experiments, participants discriminated between two duration stimuli. Experiments 1-5 employed auditory stimuli, and Experiment 6 employed visual stimuli. Experiments 1 and 2 combined each of the two tasks with an adaptive and a nonadaptive procedure for threshold estimation. Experiment 3 varied the distribution of the comparison levels, whereas Experiment 4 employed random interstimulus intervals. Experiments 5 and 6 examined the influence of the presentation order of the standard and comparison stimuli. Results indicate that both the adaptive and the nonadaptive procedures yield virtually identical DL estimates; yet, the 2AFC task produces consistently larger DLs than does the reminder task. In addition, DL increases when the standard occurs in the second rather than in the first stimulus position. In order to account for these results, we assume that participants use an internal standard instead of the actually presented standard as a reference for their judgment.