Distributed and focused attention: neuropsychological evidence for separate attentional mechanisms when counting and estimating

Evidence is presented for 2 modes of attention operating in simultanagnosia. The authors examined visual enumeration in a patient, GK, who has severe impairments in serially scanning across a scene and is unable to count the numbers of items in visual displays. However, GK's ability to judge the relative magnitude of 2 displays was consistently above chance, even when overall luminosity did not vary with the number of items present. In addition, several variables had a differential impact on GK's counting and magnitude estimation. Magnitude estimation but not counting was facilitated by using elements that grouped more easily and by presenting the elements in regular configurations. In contrast, counting was facilitated by placing the elements in different colors while magnitude estimation was disrupted. Also GK's performance on magnitude estimation tasks was disrupted by asking him to count the elements present. The data suggest that GK can process visual stimuli in either a focused or distributed attention mode. When in a focused attention mode, performance is limited by poor serial scanning of attention due to an impaired explicit representation of visual space.     

Experience-guided attention: Uniform and implicit

Frequently finding a visual search target in one region of space induces a spatial attentional bias toward that region. Past studies on this effect typically tested fewer than 20 participants. The small sample prevents an investigation of two properties of learning: visual field uniformity and role of explicit awareness. Pooling data from multiple studies, here we examined location probability learning from ~120,000 visual search trials across 420 participants. Participants performed a serial search task. Unbeknownst to them, the target was disproportionately likely to appear in one visual quadrant. Location probability learning (LPL) was measured as the difference in reaction time to targets in the high-probability “rich” quadrant and the low-probability “sparse” quadrants. Results showed a lack of visual field effect. LPL was equivalent for “rich” quadrant in the upper left, upper right, lower left, and lower right. Learning did not induce a hotspot diagonal to the “rich” quadrant. To the contrary, RT was the longest in the diagonal quadrant. Recognition rate of the “rich” quadrant was above chance. However, recognition accuracy was unrelated to the size of LPL. Implicit learning induces visual-field-independent changes in spatial attention.     

The relationship between divided attention and implicit memory: a meta-analysis

This article reports a meta-analysis comparing the size of repetition priming in full and divided-attention (DA) conditions. The main analysis included 38 effect sizes (ES) extracted from 21 empirical studies, for a total of 2074 (full-attention) and 2148 (divided-attention) participants. The mean weighted ES was 0.357 (95% CI = 0.278–0.435), indicating that divided attention produced a small, but significant, negative effect on implicit memory. Overall, the distinction between identification and production priming provided the best fit to empirical data (with the effect of DA being greater for production tests), whereas there was no significant difference between perceptual and conceptual priming. A series of focused contrasts suggested that word-stem completion might be influenced by lexical–conceptual processes, and that perceptual identification might involve a productive component. Implications for current theories of implicit memory are discussed.     

Space-, object-, and feature-based attention interact to organize visual scenes

Biased-competition accounts of attentional processing propose that attention arises from distributed interactions within and among different types of perceptual representations (e.g., spatial, featural, and object-based). Although considerable research has examined the facilitation in processing afforded by attending selectively to spatial locations, or to features, or to objects, surprisingly little research has addressed a key prediction of the biased-competition account: that attending to any stimulus should give rise to simultaneous interactions across all the types of perceptual representations encompassed by that stimulus. Here we show that, when an object in a visual display is cued, space-, feature-, and object-based forms of attention interact to enhance processing of that object and to create a scene-wide pattern of attentional facilitation. These results provide evidence to support the biased-competition framework and suggest that attention might be thought of as a mechanism by which multiple, disparate bottom-up, and even top-down, visual perceptual representations are coordinated and preferentially enhanced.     

Switching attention between modalities: further evidence for visual dominance

The present study examined cross-modal selective attention using a task-switching paradigm. In a series of experiments, we presented lateralized visual and auditory stimuli simultaneously and asked participants to make a spatial decision according to either the visual or the auditory stimulus. We observed consistent cross-modal interference in the form of a spatial congruence effect. This effect was asymmetrical, with higher costs when responding to auditory than to visual stimuli. Furthermore, we found stimulus-modality-shift costs, indicating a persisting attentional bias towards the attended stimulus modality. We discuss our findings with respect to visual dominance, directed-attention accounts, and the modality-appropriateness hypothesis.     

Behavioral evidence for task-dependent "what" versus "where" processing within and across modalities

Task-dependent information processing for the purpose of recognition or spatial perception is considered a principle common to all the main sensory modalities. Using a dual-task interference paradigm, we investigated the behavioral effects of independent information processing for shape identificationand localization ofobject features within and across vision and touch. In Experiment 1, we established that color and texture processing (i.e., a "what" task) interfered with both visual and haptic shape-matching tasks and that mirror image and rotation matching (i.e., a "where" task) interfered with a feature-location-matching task in both modalities. In contrast, interference was reduced when a "where" interference task was embedded in a "what" primary task and vice versa. In Experiment 2, we replicated this finding within each modality, using the same interference and primary tasks throughout. In Experiment 3, the interference tasks were always conducted in a modality other than the primary task modality. Here, we found that resources for identification and spatial localization are independent of modality. Our findings further suggest that multisensory resources for shape recognition also involve resources for spatial localization. These results extend recent neuropsychological and neuroimaging findings and have important implications for our understanding of high-level information processing across the human sensory systems.     

Further evidence for systematic reliability differences between explicit and implicit memory tests

Meier and Perrig (2000) as well as Buchner and Wippich (2000) have shown that simple dissociations between explicit and implicit memory measures need not reflect functional dissociations of hypothetical underlying memory systems. Instead, such dissociations may also result from the fact that some widely used implicit memory measures are simply less reliable than the explicit measures with which they have been compared. We extend this argument in two ways. First, we show that illusion-based memory measures such as the priming measures derived from fame andpreference judgement tasks are also subject to the reliability problem. Second, we show that yes-no and two-alternative forced-choice paradigms should, and in fact do, yield virtually identical results as far as the reliability of the memory tests is concerned.     

Paying attention to attention: evidence for an attentional contribution to the size congruity effect

Understanding the mechanisms supporting our comprehension of magnitude information represents a key goal in cognitive psychology. A major phenomenon employed in the pursuit of this goal has been the physical size congruity effect—namely, the observation that comparing the relative numerical sizes of two numbers is influenced by their relative physical sizes. The standard account of the physical size congruity effect attributes it to the automatic influence of the comparison of irrelevant physical magnitudes on numerical judgments. Here we develop an alternative account of this effect on the basis of the operation of attention in the typical size congruity display and the temporal dynamics of number comparison. We also provide a test of a number of predictions derived from this alternative account by combining a physical size congruity manipulation with a manipulation designed to alter the operation of attention within the typical size congruity display (i.e., a manipulation of the relative onsets of the digits). This test provides evidence consistent with an attentional contribution to the size congruity effect. Implications for our understanding of magnitude and the interactions between attention and magnitude are discussed.     

Contingency learning without awareness: evidence for implicit control

The results of four experiments provide evidence for controlled processing in the absence of awareness. Participants identified the colour of a neutral distracter word. Each of four words (e.g., MOVE) was presented in one of the four colours 75% of the time (Experiments 1 and 4) or 50% of the time (Experiments 2 and 3). Colour identification was faster when the words appeared in the colour they were most often presented in relative to when they appeared in another colour, even for participants who were subjectively unaware of any contingencies between the words and the colours. An analysis of sequence effects showed that participants who were unaware of the relation between distracter words and colours nonetheless controlled the impact of the word on performance depending on the nature of the previous trial. A block analysis of contingency-unaware participants revealed that contingencies were learned rapidly in the first block of trials. Experiment 3 showed that the contingency effect does not depend on the level of awareness, thus ruling out explicit strategy accounts. Finally, Experiment 4 showed that the contingency effect results from behavioural control and not from semantic association or stimulus familiarity. These results thus provide evidence for implicit control.     

The recovery of identity and relative position from visual input: Further evidence for the independence of processing of what and where

Four experiments examined the manner in which item identity and relative position are recovered from visual input. A successivesame/different matching paradigm was designed in which each trial contained a prime and a target display. Each display contained a reference object (i.e., a “+”) and a located object (i.e., a letter, which fell to either the right or the left of the “+”). In Experiment 1, subjects carried out identity judgments on the letters. Experiment 2 examined relative position judgments; in Experiment 3, subjects had to judge both item identity and relative position information. Overall, these initial data suggested that identity and positional information are recovered via independent mechanisms and that these operate concurrently. This suggestion was supported by the results of Experiment 4, which in turn disconfirmed an alternative response account of performance.     

Divided attention between lyrics and tunes of operatic songs: evidence for independent processing.

Excerpts from French operatic songs were used to evaluate the extent to which language and music compete for processing resources. Do these two dimensions conflict? Are they integrated into a single percept? Or are they independent? The final word of each excerpt was either semantically congruous or incongruous relative to the prior linguistic context and was sung either in or out of key. Participants were asked to detect either the semantic or the melodic incongruity (single task) or both (dual task). We predicted a dual-task deficit if these tasks conflicted and no deficit if they were either independent or integrated. In order to distinguish between these last two outcomes, trial-by-trial contingency analyses were also computed, predicting no correlation if the tasks were conflicting or independent, a positive correlation under the assumption of integration and a negative correlation if dividing attention is impossible. Our results show similar levels of performance in single and dual tasks and no correlation between dual-task judgments, thus suggesting that semantic and melodic aspects of language are processed by independent systems. In addition, a comparison between musicians and nonmusicians shows that these conclusions are independent of musical expertise.     

Selective reaching: evidence for action-centered attention.

Most studies of selective attention briefly present static 2-dimensional stimuli and require arbitrary responses such as verbal naming or a keypress. Many of our perceptual-motor interactions with the environment, however, require reaching directly toward an object while ignoring other objects in the scene. A series of experiments examines selective attention in the latter reaching situation. Effects previously observed in the traditional experimental procedures were obtained, suggesting that the models developed (which propose inhibitory mechanisms, e.g.) apply to ecologically valid situations. Attention accesses action-centered internal representations during such tasks.     

From fear to love: individual differences in implicit spider associations

The Implicit Association Test (IAT) was used to investigate automatic fear associations in fear of spiders. Fear associations toward spiders were measured among spider fearful and nonfearful participants (Experiment 1) as well as among nonfearfuls and spider enthusiasts (Experiment 2). It was shown that the IAT is sensitive to personal automatic fear associations and therefore distinguishes between high-fearful, nonfearful, and enthusiastic participants. Moreover, implicit spider associations measured by the IAT predicted avoidance behavior beyond self-reports. The results of Experiment 2 provide additional support for the argument that implicit spider associations are different from general stereotypes or knowledge about spiders.     

The association between psychological distance and construal level: evidence from an implicit association test

According to construal level theory (N. Liberman, Y. Trope, & E. Stephan, in press; Y. Trope & N. Liberman, 2003), people use a more abstract, high construal level when judging, perceiving, and predicting more psychologically distal targets, and they judge more abstract targets as being more psychologically distal. The present research demonstrated that associations between more distance and higher level of construal also exist on a pure conceptual level. Eight experiments used the Implicit Association Test (IAT; A. G. Greenwald, D. E. McGhee, & J. L. K. Schwartz, 1998) to demonstrate an association between words related to construal level (low vs. high) and words related to four dimensions of distance (proximal vs. distal): temporal distance, spatial distance, social distance, and hypotheticality. In addition to demonstrating an association between level of construal and psychological distance, these findings also corroborate the assumption that all 4 dimensions of psychological distance are related to level of construal in a similar way and support the notion that they all are forms of psychological distance.     

Domain-specificity and theory of mind: evaluating neuropsychological evidence

Humans' unique aptitude for reasoning about mental states, known as Theory of Mind (ToM), can help explain the unique character of human communication and social interaction. ToM has been studied extensively in children, but there is no clear account of the cognitive basis of ToM in adults. Evidence from functional imaging and neuropsychology is beginning to address this surprising gap in our understanding, and this evidence is often thought to favour a domain-specific or modular architecture for ToM. We present a systematic approach to this issue for the paradigmatic case of belief reasoning, and argue that neuropsychological data provide no clear evidence for domain-specificity or modularity. Progress in understanding ToM requires new tasks that isolate potentially distinct components of this complex ability.     

Categorization and affect: evidence for intra-hemispheric interactions

Both emotional reactivity and categorization have long been studied within the framework of hemispheric asymmetry. However, little attempt has been made to integrate both research areas using any form of neuropsychological research, despite behavioral data suggesting a consistent relationship between affective and categorization processes. The primary goal of the current study was to examine the possibility of a laterally mediated interaction between emotional reactivity and the cognitive process of categorization. Using a split visual fields categorization task combined with affect inducing procedures, we hypothesized that the relationship between state affect and categorization would be dependent on the nature of state affect and on the hemisphere targeted. Results offered support for this hypothesis, showing that state affect related changes in categorization appeared only in the hemisphere commonly associated with both a specific affective state and categorization strategy employed. Findings are discussed in terms of possible evidence for a hemispheric arousal effect underlying the relationship between affect and categorization.     

Convergent behavioral and neuropsychological evidence for a distinction between identification and production forms of repetition priming

Four experiments examined a distinction between kinds of repetition priming which involve either the identification of the form or meaning of a stimulus or the production of a response on the basis of a cue. Patients with Alzheimer's disease had intact priming on picture-naming and category-exemplar identification tasks and impaired priming on word-stem completion and category-exemplar production tasks. Division of study-phase attention in healthy participants reduced priming on word-stem completion and category-exemplar production tasks but not on picture-naming and category-exemplar identification tasks. The parallel dissociations in normal and abnormal memory cannot be explained by implicit-explicit or perceptual-conceptual distinctions but are explained by an identification-production distinction. There may be separable cognitive and neural bases for implicit modulation of identification and production forms of knowledge.