Learning efficient visual search for stimuli containing diagnostic spatial configurations and color-shape conjunctions

Visual search is often slow and difficult for complex stimuli such as feature conjunctions. Search efficiency, however, can improve with training. Search for stimuli that can be identified by the spatial configuration of two elements (e.g., the relative position of two colored shapes) improves dramatically within a few hundred trials of practice. Several recent imaging studies have identified neural correlates of this learning, but it remains unclear what stimulus properties participants learn to use to search efficiently. Influential models, such as reverse hierarchy theory, propose two major possibilities: learning to use information contained in low-level image statistics (e.g., single features at particular retinotopic locations) or in high-level characteristics (e.g., feature conjunctions) of the task-relevant stimuli. In a series of experiments, we tested these two hypotheses, which make different predictions about the effect of various stimulus manipulations after training. We find relatively small effects of manipulating low-level properties of the stimuli (e.g., changing their retinotopic location) and some conjunctive properties (e.g., color-position), whereas the effects of manipulating other conjunctive properties (e.g., color-shape) are larger. Overall, the findings suggest conjunction learning involving such stimuli might be an emergent phenomenon that reflects multiple different learning processes, each of which capitalizes on different types of information contained in the stimuli. We also show that both targets and distractors are learned, and that reversing learned target and distractor identities impairs performance. This suggests that participants do not merely learn to discriminate target and distractor stimuli, they also learn stimulus identity mappings that contribute to performance improvements.     

Learning to ignore: Acquisition of sustained attentional suppression

We examined whether the selection mechanisms committed to the suppression of ignored stimuli can be modified by experience to produce a sustained, rather than transient, change in behavior. Subjects repeatedly ignored the shape of stimuli, while attending to their color. On subsequent attention to shape, there was a robust and sustained decrement in performance that was selective to when shape was ignored across multiple-colortarget contexts, relative to a single-color-target context. Thus, amount of time ignored was not sufficient to induce a sustained performance decrement. Moreover, in this group, individual differences in initial color target selection were associated with the subsequent performance decrement when attending to previously ignored stimuli. Accompanying this sustained decrement in performance was a transfer in the locus of suppression from an exemplar (e.g., a circle) to a feature (i.e., shape) level of representation. These data suggest that learning can influence attentional selection by sustained attentional suppression of ignored stimuli.     

Stimulus–response bindings code both abstract and specific representations of stimuli: evidence from a classification priming design that reverses multiple levels of response representation

Repetition priming can be caused by the rapid retrieval of previously encoded stimulus–response (S–R) bindings. S–R bindings have recently been shown to simultaneously code multiple levels of response representation, from specific Motor-actions to more abstract Decisions (“yes”/”no”) and Classifications (e.g., “man-made”/”natural”). Using an experimental design that reverses responses at all of these levels, we assessed whether S–R bindings also code multiple levels of stimulus representation. Across two experiments, we found effects of response reversal on priming when switching between object pictures and object names, consistent with S–R bindings that code stimuli at an abstract level. Nonetheless, the size of this reversal effect was smaller for such across-format (e.g., word–picture) repetition than for within-format (e.g., picture–picture) repetition, suggesting additional coding of format-specific stimulus representations. We conclude that S–R bindings simultaneously represent both stimuli and responses at multiple levels of abstraction.     

The dimensional arrow: Agreement in directional mapping of dimensions among Mandarin Chinese- and English-speakers

We present evidence that English- and Mandarin-speakers agree about how to map dimensions (e.g., size and clarity) to vertical space and that they do so in a directional way. We first developed visual stimuli for four dimensions—size, clarity, complexity, and darkness—and in each case we varied the stimuli to express a range of the dimension (e.g., there were five total items expressing the range covering big, medium, and small). In our study, English- and Mandarin-speakers mapped these stimuli to an unlabelled vertical scale. Most people mapped dimensional endpoints in similar ways; using size as a standard, we found that the majority of participants mapped the clearest, most complex, and darkest items to the same end of the vertical scale as they mapped the biggest items. This indicates that all four dimensions have a weighted or unmarked end (i.e., all are directional or polar). The strong similarities in polarity across language groups contrasted with group differences on a lexical task, for which there was little cross-linguistic agreement about which comparative words to use to describe stimulus pairs (e.g., “bigger” vs. “smaller”). Thus, we found no evidence in this study that the perception of these dimensions is influenced by language.     

Contingent attentional capture occurs by activated target congruence

Contingent attentional capture occurs when a stimulus property captures an observer's attention, usually related to the observer's top-down attentional set for target-defining properties. In this study, we examined whether contingent attentional capture occurs for a distractor that does not share the target-defining property at a physical level, but does share that property at an abstract level of representation. In a rapid serial visual presentation stream, we defined the target by color (e.g., a green-colored Japanese kanji character). Before the target onset, we presented a distractor that referred to the target-defining color (e.g., a white-colored character meaning "green"). We observed contingent attentional capture by the distractor, which was reflected by a deficit in identifying the subsequent target. This result suggests that because of the attentional set, stimuli were scanned on the basis of the target-defining property at an abstract semantic level of representation.     

Space and Time in the Child's Mind: Evidence for a Cross-Dimensional Asymmetry

What is the relationship between space and time in the human mind? Studies in adults show an asymmetric relationship between mental representations of these basic dimensions of experience: Representations of time depend on space more than representations of space depend on time. Here we investigated the relationship between space and time in the developing mind. Native Greek‐speaking children watched movies of two animals traveling along parallel paths for different distances or durations and judged the spatial and temporal aspects of these events (e.g., Which animal went for a longer distance, or a longer time?). Results showed a reliable cross‐dimensional asymmetry. For the same stimuli, spatial information influenced temporal judgments more than temporal information influenced spatial judgments. This pattern was robust to variations in the age of the participants and the type of linguistic framing used to elicit responses. This finding demonstrates a continuity between space‐time representations in children and adults, and informs theories of analog magnitude representation.     

Talking while looking: On the encapsulation of output system representations

The idea that the human mind can be divided into distinct (but interacting) functional modules is an important presupposition in many theories of cognition. While previous research on modularity predominantly studied input domains (e.g., vision) or central processes, the present study focused on cognitive representations of output domains. Specifically, we asked to what extent output domain representations are encapsulated (i.e., immune to influence from other domains, representing a key feature of modularity) by studying determinants of interference between simultaneous action demands (oculomotor and vocal responses). To examine the degree of encapsulation, we compared single- vs. dual-response performance triggered by single stimuli. Experiment 1 addressed the role of stimulus modality under dimensionally overlapping response requirements (stimuli and responses were spatial and compatible throughout). In Experiment 2, we manipulated the presence of dimensional overlap across responses. Substantial performance costs associated with dual-response (vs. single-response) demands were observed across response modalities, conditions, and experiments. Dimensional overlap combined with shared spatial codes across responses enabled response-code priming (i.e., beneficial crosstalk between output domains). Overall, the results are at odds with the idea of strong encapsulation of output system representations and show how processing content determines the extent of interdependency between output domains in cognition.     

What happens to our representation of identity as familiar faces age? Evidence from priming and identity aftereffects

Matching identity in images of unfamiliar faces is error prone, but we can easily recognize highly variable images of familiar faces – even images taken decades apart. Recent theoretical development based on computational modelling can account for how we recognize extremely variable instances of the same identity. We provide complementary behavioural data by examining older adults’ representation of older celebrities who were also famous when young. In Experiment 1, participants completed a long-lag repetition priming task in which primes and test stimuli were the same age or different ages. In Experiment 2, participants completed an identity after effects task in which the adapting stimulus was an older or young photograph of one celebrity and the test stimulus was a morph between the adapting identity and a different celebrity; the adapting stimulus was the same age as the test stimulus on some trials (e.g., both old) or a different age (e.g., adapter young, test stimulus old). The magnitude of priming and identity after effects were not influenced by whether the prime and adapting stimulus were the same age or different age as the test face. Collectively, our findings suggest that humans have one common mental representation for a familiar face (e.g., Paul McCartney) that incorporates visual changes across decades, rather than multiple age-specific representations. These findings make novel predictions for state-of-the-art algorithms (e.g., Deep Convolutional Neural Networks).     

The free classification of analyzable and unanalyzable stimuli

The free classification of two-dimensional analyzable and unanalyzable stimuli was investigated. Analyzable stimuli consist of dimensions which are distinct and phenomenally separable (e.g., colored geometric forms); unanalyzable stimuli consist of two dimensions which are not distinct, not phenomenally separable, and which are probably perceived as a unitary dimension (e.g., Munsell colors). In the first experiment, Ss judged the similarity between each stimulus pair for both types of stimuli. The results replicated previous work in showing that the city-block metric was appropriate for the analyzable stimuli and that the euclidean metric was appropriate for unanalyzable stimuli. In the second experiment, Ss classified sets of analyzable and unanalyzable stimuli into two or three groups in any way they wished. For analyzable stimuli, classification was based on the dimensional structure-stimuli which alter the dimensional structure by defining another dimension change classification. For unanalyzable stimuli, classification was based on the similarity structure-stimuli which alter the similarity structure change classification.     

Attentional repulsion effect despite a colour-based control set

A salient distractor can have a twofold effect on concurrent visual processes; it can both reduce the processing efficiency of the relevant target (e.g., increasing response time) and distort the spatial representation of the display (e.g., misperception of a target location). Previous work has shown that knowledge of the key feature of visual targets can eliminate the effect of salient distractors on processing efficiency. For instance, knowing that the target of interest is red (i.e., having an attentional control set for red) can eliminate the cost of green distractors on the speed of response to the target. The present study shows that the second mark of irrelevant salient distractors, i.e., distortions in spatial representation, is resistant to such top-down control. Using the attentional repulsion effect, we examined the influence of salient distractors on target localization. Observers had a colour-based control set and the distractors either matched or mismatched with the control set. In the first two experiments, we found systematic mislocalization of targets away from the peripheral distractors (i.e., an attentional repulsion effect). Critically, the effect was caused by distractors that both matched and mismatched the control set. A third experiment, using the same stimuli, found that processing efficiency was perfectly resistant to distractors that did not match the control set, consistent with previous work. Together, the present findings suggest that although top-down control can eliminate the cost of a salient distractor on processing efficiency, it does so without eliminating the distractor's influence on the spatial representation of the display.     

Religious versus reflective priming and susceptibility to the conjunction fallacy

The effect of religious priming has been studied in relation to a number of variables, most extensively with prosocial behavior. The effects of priming on cognitive domains, however, are relatively understudied. The present study examined the effects of religious priming, compared with reflective and neutral priming, on the conjunction fallacy. Participants were randomly assigned to 1 of the 3 priming conditions. Priming was presented through the scrambled sentence task in which participants were required to rearrange words of a religious (e.g., pray), reflective (e.g., reason), or neutral (e.g., paper) content. The conjunction fallacy was measured by a task containing 1 problem. Results indicated that those undergoing the religious prime were significantly more likely to commit the conjunction fallacy compared with those in the reflective priming group. Situations in which reasoning is integral may benefit from knowing the immediate effects of religious versus reflective stimuli in the environment.     

Retrieval savings with nonidentical elements: The case of simple addition and subtraction

The identical elements (IE) theory of fact representation (Rickard, 2005) proposes that memorized facts that are composed of identical elements (e.g., 6 × 8 = 48 and 8 × 6 = 48) share a common representation in memory, whereas facts with nonidentical elements (e.g., 6 × 8 = 48 and 48 ÷ 8 = 6) are represented separately in memory. The IE model has been successfully applied to the transfer of practice in simple multiplication and division, in transition from procedure-based to retrieval-based performance, and in cued episodic recall. In the present article, we examined the effects of practicing simple addition problems (e.g., 3 + 6 = 9) on the performance of corresponding subtraction problems (9 − 6 = 3), and vice versa. According to IE theory, there should be no transfer of retrieval savings between addition and subtraction facts if performance is based on discrete IE fact representations. Cross-operation response time savings were observed, however, for both small, well-memorized problems (e.g., practice 3 + 2, test 5 − 2) and larger problems (6 + 8, 14 − 6), and they were statistically robust when trials that were self-reported as direct retrieval were analyzed. The transfer of retrieval practice savings between facts with nonidentical elements challenges IE theory as a comprehensive model of transfer in memory retrieval.     

Conjunctive representations,the hippocampus,and contextual fear conditioning

The context in which events occur can be represented as both (1) a set of independent features, the feature representation view, and (2) a set of features bound into a unitary representation, the conjunction representation view. It is assumed that extrahippocampal (e.g., neocortical) areas provide a basis for feature representations, but the hippocampal formation makes an essential contribution to the automatic storage of conjunctive representations. We develop this dual-representation view and explore its implications for hippocampal contributions to contextual fear conditioning processes. To this end, we discuss how our framework can resolve some of the conflicts in the recent literature relating the hippocampus to contextual fear conditioning. We also present new data supporting the role of a key mechanism afforded by conjunctive representations—pattern completion (the ability of a subset of a memory pattern to activate the complete memory)—in contextual fear conditioning. As is implied by this mechanism, we report that fear can be conditioned to the memory representation of a context that is not actually present at the time of shock. Moreover, this result is predicted by our computational model of cortical and hippocampal function. We suggest that pattern completion demonstrated in animals and by our model provides a mechanistic bridge to human declarative memory.     

Symbolic- and response-related contributions to blindness to compatible stimuli

Blindness to compatible stimuli refers to poorer target identification (e.g., right-pointing arrowhead) following compatible stimuli (e.g., right arrows; Stevanovski, Oriet, & Jolic?ur, 2003) and compatible responses (e.g., right key press; Müsseler & Hommel, 1997a and 1997b). To clarify the role of the response in this effect, we examined the impact of adding or removing an overt response. In three experiments, subjects saw an arrow cue (that sometimes required a response) followed by a brief, masked arrowhead, which was reported on all trials. In all experiments, making a response increased the magnitude of the blindness effect. Furthermore, “no response” performance was unaffected by whether subjects had previously responded to the cue. Results favour a two-factor symbolic- plus response-related activation model over a purely symbolic activation model.     

Sources of Cognitive Inflexibility in Set-Shifting Tasks: Insights Into Developmental Theories From Adult Data

Two experiments examined processes underlying cognitive inflexibility in set-shifting tasks typically used to assess the development of executive function in children. Adult participants performed a Flexible Item Selection Task (FIST) that requires shifting from categorizing by one dimension (e.g., color) to categorizing by a second orthogonal dimension (e.g., shape). The experiments showed performance of the FIST involves suppression of the representation of the ignored dimension; response times for selecting a target object in an oddity task immediately following were slower when the oddity target was the previously ignored stimulus of the FIST. However, proactive interference from the previously relevant stimulus dimension also impaired responding. The results are discussed with respect to two prominent theories of the source of difficulty for children and adults on dimensional shifting tasks: attentional inertia and negative priming. In contrast to prior work emphasizing one process over the other, the findings indicate that difficulty in the FIST, and by extension other set-shifting tasks, can be attributed to both the need to shift away from the previously attended representation (attentional inertia) and the need to shift to the previously ignored representation (negative priming). Results are discussed in relation to theoretical explanations for cognitive inflexibility in adults and children.     

Number-of-features effects and semantic processing

Participants list many semantic features for some concrete nouns (e.g., lion) and fewer for others (e.g., lime; McRae, de Sa, & Seidenberg, 1997). Pexman, Lupker, and Hino (2002) reported faster lexical decision and naming responses for high number of features (NOF) words than for low-NOF words. In the present research, we investigated the impact of NOF on semantic processing. We observed NOF effects in a self-paced reading task when prior context was not congruent with the target word (Experiment 1) and in a semantic categorization task (concrete vs. abstract; Experiment 2A). When we narrowed our stimuli to include high- and low-NOF words from a single category (birds), we found substantial NOF effects that were modulated by the specificity of the categorization task (Experiments 3A, 3B, and 3C). We argue that these results provide support for distributed representation of word meaning.     

Sensorimotor simulations underlie conceptual representations: Modality-specific effects of prior activation

According to the perceptual symbols theory (Barsalou, 1999), sensorimotor simulations underlie the representation of concepts. Simulations are componential in the sense that they vary with the context in which the concept is presented. In the present study, we investigated whether representations are affected by recent experiences with a concept. Concept names (e.g., APPLE) were presented twice in a property verification task with a different property on each occasion. The two properties were either from the same perceptual modality (e.g.,green, shiny) or from different modalities (e.g.,tart, shiny). All stimuli were words. There was a lag of several intervening trials between the first and second presentation. Verification times and error rates for the second presentation of the concept were higher if the properties were from different modalities than if they were from the same modality.     

THE PERVERSITY OF INANIMATE OBJECTS: STIMULUS CONTROL BY INCIDENTAL MUSICAL NOTATION

Social cognition research suggests that incidental, environmental stimuli (e.g., business suits) can nonconsciously influence the degree to which behavioral dispositions (e.g., competitiveness) are expressed. Similarly, cognitive research suggests that incidental action-related objects (e.g., hammers) can prime action plans that then affect the speed with which a concurrent, intended action (e.g., power grip) is executed. However, whether incidental stimuli can instigate actions that run counter to one's current goals has yet to be determined. Moving beyond indirect effects, we show that such stimuli can directly cause the expression of undesired actions: Incidental stimuli resembling musical notation caused the systematic expression of unintended key presses in musicians, but not in nonmusicians. Moreover, the effect was found even when targets and distracters bore no apparent perceptual or semantic relation. We discuss the implications of these findings for models of action production and for social-cognitive concepts (e.g., applicability) regarding the limits of nonconscious processing.     

The initial representation in reasoning towards an interpretation of conditional sentences

All accounts of human reasoning (whether presented at the symbolic or subsymbolic level) have to reckon with the temporal organization of the human processing systems and the ephemeral nature of the representations it uses. We present three new empirical tests for the hypothesis that people commence the interpretational process by constructing a minimal initial representation. In the case of if A then C the initial representation captures the occurrence of the consequent, C, within the context of the antecedent, A. Conditional inference problems are created by a categorical premise that affirms or denies A or C. The initial representation allows an inference when the explicitly represented information matches (e.g., the categorical premise A affirms the antecedent "A") but not when it mismatches (e.g., "not-A" denies A). Experiments 1 and 2 confirmed that people tend to accept the conclusion that "nothing follows" for the denial problems, as indeed they do not have a determinate initial-model conclusion. Experiment 3 demonstrated the other way round that the effect of problem type (affirmation versus denial) is reduced when we impede the possibility of inferring a determinate conclusion on the basis of the initial representation of both the affirmation and the denial problems.