Geometry,landmarks and the cerebral hemispheres: 2D spatial reorientation in split‐brain patients

A right‐hemispheric superiority in spatial encoding based on geometric cues has been largely documented in a variety of species, together with a left‐hemispheric specialization for encoding based on landmarks. In humans, hemispheric asymmetries for spatial encoding have been little explored. In this study, we compared a patient with a complete callosal resection (D.D.C.) and a patient with a wide callosal resection saving the splenium (A.P.), with healthy participants. In two 2D versions of the ‘reorientation task’, participants were asked to find the target corner of a rectangle‐shaped environment, by exploiting either geometric information alone or the combination of geometric and landmark information. In Experiment 1, the landmark consisted of a coloured side of the rectangle; in Experiment 2, this cue was replaced by a coloured disc located inside the rectangle. In both experiments, the rectangular shape ensured the geometric cue. D.D.C. was always unable to recall the target, whereas A.P. correctly solved the task when only the geometric information was available, without difference with respect to the controls. Importantly, the performance of A.P. did not differ from controls’ when the right hemisphere was tested with the landmark cues (the task being carried out using the left hand), whereas when the left hemisphere was tested (right‐hand session) his performance was worse than controls’ with the coloured side of the space, but it was better than controls’ with the coloured disc. The results are discussed comparing them with data collected on other species, and with theories of spatial processing.     

Retrospective cues based on object features improve visual working memory performance in older adults

Research with younger adults has shown that retrospective cues can be used to orient top-down attention toward relevant items in working memory. We examined whether older adults could take advantage of these cues to improve memory performance. Younger and older adults were presented with visual arrays of five colored shapes; during maintenance, participants were presented either with an informative cue based on an object feature (here, object shape or color) that would be probed, or with an uninformative, neutral cue. Although older adults were less accurate overall, both age groups benefited from the presentation of an informative, feature-based cue relative to a neutral cue. Surprisingly, we also observed differences in the effectiveness of shape versus color cues and their effects upon post-cue memory load. These results suggest that older adults can use top-down attention to remove irrelevant items from visual working memory, provided that task-relevant features function as cues.     

Event-related potentials reveal the relations between feature representations at different levels of abstraction

In this paper, we use behavioural methods and event-related potentials (ERPs) to explore the relations between informational and instantiated features, as well as the relation between feature abstraction and rule type. Participants are trained to categorize two species of fictitious animals and then identify perceptually novel exemplars. Critically, two groups are given a perfectly predictive counting rule that, according to Hannah and Brooks (2009. Featuring familiarity: How a familiar feature instantiation influences categorization. Canadian Journal of Experimental Psychology/Revue Canadienne de Psychologie Expérimentale, 63, 263–275. Retrieved from http://doi.org/10.1037/a0017919), should orient them to using abstract informational features when categorizing the novel transfer items. A third group is taught a feature list rule, which should orient them to using detailed instantiated features. One counting-rule group were taught their rule before any exposure to the actual stimuli, and the other immediately after training, having learned the instantiations first. The feature-list group were also taught their rule after training. The ERP results suggest that at test, the two counting-rule groups processed items differently, despite their identical rule. This not only supports the distinction that informational and instantiated features are qualitatively different feature representations, but also implies that rules can readily operate over concrete inputs, in contradiction to traditional approaches that assume that rules necessarily act on abstract inputs.     

Developmental changes in the recognition of faces and facial features

The view that, as children get older, there is a decline in the use of feature‐based forms of face processing to more configurational forms of processing was examined by asking 6‐year‐old and 9‐year‐old children to judge which of two photographs matches an identical probe photograph. The probe and test stimuli were either photographs of whole faces or photographs of isolated facial features. Within this standard method, the stimuli also systematically varied in terms of the familiarity of the faces shown and in the orientation of presentation, both factors that have been interpreted as effecting configurational encoding. A number of age‐related effects are observed: (a) older children are better at recognizing whole faces than younger children, (b) older children exhibit a clear face inversion effect with whole faces while the younger children are equally adept at identifying upright and inverted whole faces, and (c) analysis of the recognition rates associated with the individual features reveals that younger children are better than older children when asked to recognize eye regions. It is argued that the data support the view that as children get older there is a change in the forms of piecemeal encoding employed and an increase in configurational processing. Copyright © 2000 John Wiley & Sons, Ltd.     

The role of landmarks in cotton-top tamarin spatial foraging: evidence for geometric and non-geometric features

We report experiments on captive cotton-top tamarins (Saguinus oedipus) designed to explore two components of spatial foraging. First, do tamarins have the capacity to extract geometric information concerning the spatial relationship between a landmark and a piece of food located above or below it? Second, when tamarins use a landmark to find a target location, what non-geometric features of the landmark do they encode? To explore these problems, we created an artificial jungle environment and trained subjects to find food either above or below a target object (i.e., landmark). Once subjects successfully located the food, we transformed various features associated with the landmark, including its color, orientation, and shape; we also manipulated the landmark-food reward distance, the overall shape of the jungle, and the number and position of landmarks. Results showed that the tamarins' success in finding the food reward was not affected by landmark color, orientation, number, or overall shape of the jungle, suggesting that with respect to the particular test conditions, these features are not relevant to the representation of a landmark. Subjects also generalized to novel landmark-food distances, suggesting that they had integrated geometric (i.e., above/below) with non-geometric (i.e., color/shape) features. Performance was negatively affected by changes to the shape of the landmark, indicating that this feature is critical to the representation of a landmark. Accepted after revision: 7 August 2001 Electronic Publication     

特征概率影响多维和少维类别的分类学习和特征学习

探讨了特征概率对多维和少维类别的分类学习和特征学习的效果及策略的影响。结果表明高特征概率条件下,多维比少维类别的分类学习更容易,而且学到更多的特征知识,多维条件下人们更倾向于整体性加工策略,而少维条件下人们倾向于分析性加工策略。低特征概率条件下,多维比少维类别的分类学习和特征学习都困难,且两种条件下人们都倾向于采取分析性加工策略。     

Analyzing feature distinctiveness in the processing of living and non-living concepts in Alzheimer’s disease

The conceptual structure account (CSA) is a model specifying the role of the living and non-living domain dichotomy in the structure of semantic memory. According to this model, feature distinctiveness and the perceptual–functional inter-correlation of concepts are assumed to play a major role in impairing the ability to discriminate between living and non-living concepts in Alzheimer’s disease (AD). The hypothesis was tested in this study by using naming and sorting tasks traditionally considered as assessing distinctiveness, and a property verification task where distinctiveness and perceptual–functional inter-correlation were objectively controlled against norms especially created for this purpose. Alzheimer’s patients (n = 59) with minimal, mild or moderate dementia and normal elderly adults (n = 31) participated in the study. Overall, the findings did not support the CSA predictions. They revealed a distinctiveness effect on response accuracy with shared features dominating distinctive features regardless of domain. They also revealed more difficulties in the tasks involving effortful processes. The results stress the need to consider both cognitive demands of tasks and structural aspects of knowledge in the evaluation of semantic memory in AD.     

Sustained attention to local and global target features is different: Performance and tympanic membrane temperature

Vision researchers have investigated the differences between global and local feature perception. No one has, however, examined the role of global and local feature discrimination in sustained attention tasks. In this experiment participants performed a sustained attention task requiring either global or local letter target discriminations or watched the same displays without any work imperative. Reaction time to targets was slower when global feature discriminations were required than when local feature discriminations were required. Tympanic membrane temperature (TMT) was utilized in this study as an index of cerebral activation. Participants in the global letter detection condition had elevated post-task right TMT, indicative of reduced cerebral activation in the right hemisphere, in comparison to participants in the local letter detection or no-work imperative conditions. Both the performance and physiological results of this study indicate increased cognitive fatigue when global feature discriminations are required.     

Examining the relation between borderline personality features and social support: The mediating role of rejection sensitivity

Potential mechanisms underlying the pathway between borderline personality features and indices of social support have yet to be elaborated, despite that social difficulties are a hallmark feature of borderline personality disorder (BPD). We hypothesized that rejection sensitivity, or the tendency to anxiously anticipate and readily perceive social rejection, might be one mechanism leading to the negative social impact associated with BPD symptoms. To test this hypothesis, a sample of college students (N = 165) completed self-report measures in the laboratory. With rejection sensitivity in the model, borderline features did not directly predict number of social supports. However, borderline features indirectly predicted decreased number of social supports via increased rejection sensitivity. Conversely, borderline features directly predicted social support satisfaction but did not evidence an indirect effect through rejection sensitivity. The results of this research suggest that rejection sensitivity is an important individual difference by which borderline features leads to the lower levels of social support demonstrated in past research. Future directions, such as examining potential mediators of social support perception, are discussed.