Imperfect invariance to object translation in the discrimination of complex shapes

The positional specificity of short-term visual memory for a variety of 3-D shapes was investigated in a series of 'same'/'different' discrimination experiments, with computer-rendered stimuli displayed either at the same or at different locations in the visual field. For animal-like shapes, we found complete translation invariance, regardless of the interstimulus similarity, and irrespective of direction and size of the displacement (experiments 1 and 2). Invariance to translation was obtained also with animal-like stimuli that had been 'scrambled' by randomizing the relative locations of their parts (experiment 3). The invariance broke down when the stimuli were made to differ in their composition, but not in the shapes of the corresponding parts (experiments 4 and 5). We interpret this pattern of findings in the context of several current theories of recognition, focusing in particular on the issue of the representation of object structure.     

Similarities Between the Psychological Profiles of Complex Regional Pain Syndrome and Conversion Disorder Patients

The psychological profile of 17 Complex Regional Pain Syndrome type I (CRPS) and 20 Conversion Disorder (CD) patients were compared, using the Minnesota Multiphasic Personality Inventory (MMPI) and standardized, semistructured psychological interviews. Both groups presented abnormally high somatization scores. Low anxiety scores in both groups indicate that somatization may have served as a defense mechanism to bind anxiety. Depression was apparent in both groups, indicating that psychological distress accompany these syndromes. About one third of the participants in both groups presented comorbid Axis I disorders, mostly depression and PTSD. CRPS patients have traditionally been looked upon as suffering from mainly organic symptoms, whereas CD patients have been labeled as psychiatric patients. These results may indicate the need to reexamine the traditional classifications in respect to disorders that involve body and mind.     

Critical NoticeHumanity, Authority and the Mesmeric Ought

Virtues and Reasons: Philippa Foot and Moral Theory , edited by Rosalind Hursthouse, Gavin Lawrence and Warren Quinn     

Competitive learning in biological and artificial neural computation

In this review we will briefly discuss 'classical' competitive learning and approaches to competitive learning that involve mixtures of experts. We will then focus on competitive learning that is guided by the temporal structure that is present within the stimuli. In this context, we will describe a general principle for resource allocation and memory management, that may account for a range of psychophysical and neurophysiological findings.     

Errors in proofreading: Evidence for syntactic control of letter processing?

The present study compared the rates of detection of misspellings in content and in function words, controlling for the effects of familiarity by studying verbs that could be either content words or function words according to the context. In agreement with previous studies, it was found that errors were more readily detected in content words than in function words, thereby clearly demonstrating the importance of syntactic factors in processing the words in a text. Unlike previous studies, we did not find consistent evidence that errors changing the overall word shape were detected more easily than errors preserving word shape, and we found no evidence that the position of the error in the word affected its rate of detection. These findings were interpreted in the framework of an interactive approach to the reading process.     

Representation is representation of similarities

Advanced perceptual systems are faced with the problem of securing a principled (ideally, veridical) relationship between the world and its internal representation. I propose a unified approach to visual representation, addressing the need for superordinate and basic-level categorization and for the identification of specific instances of familiar categories. According to the proposed theory, a shape is represented internally by the responses of a small number of tuned modules, each broadly selective for some reference shape, whose similarity to the stimulus it measures. This amounts to embedding the stimulus in a low-dimensional proximal shape space spanned by the outputs of the active modules. This shape space supports representations of distal shape similarities that are veridical as Shepard's (1968) second-order isomorphisms (i.e., correspondence between distal and proximal similarities among shapes, rather than between distal shapes and their proximal representations). Representation in terms of similarities to reference shapes supports processing (e.g., discrimination) of shapes that are radically different from the reference ones, without the need for the computationally problematic decomposition into parts required by other theories. Furthermore, a general expression for similarity between two stimuli, based on comparisons to reference shapes, can be used to derive models of perceived similarity ranging from continuous, symmetric, and hierarchical ones, as in multidimensional scaling (Shepard 1980), to discrete and nonhierarchical ones, as in the general contrast models (Shepard & Arabie 1979; Tversky 1977).     

Learn locally, act globally: Learning language from variation set cues

Variation set structure - partial overlap of successive utterances in child-directed speech - has been shown to correlate with progress in children’s acquisition of syntax. We demonstrate the benefits of variation set structure directly: in miniature artificial languages, arranging a certain proportion of utterances in a training corpus in variation sets facilitated word and phrase constituent learning in adults. Our findings have implications for understanding the mechanisms of L1 acquisition by children, and for the development of more efficient algorithms for automatic language acquisition, as well as better methods for L2 instruction.     

Listening with an Accent: Speech Perception in a Second Language by Late Bilinguals

The goal of the present study was to examine functioning of late bilinguals in their second language. Specifically, we asked how native and non-native Hebrew speaking listeners perceive accented and native-accented Hebrew speech. To achieve this goal we used the gating paradigm to explore the ability of healthy late fluent bilinguals (Russian and Arabic native speakers) to recognize words in L2 (Hebrew) when they were spoken in an accent like their own, a native accent (Hebrew speakers), or another foreign accent (American accent). The data revealed that for Hebrew speakers, there was no effect of accent, whereas for the two bilingual groups (Russian and Arabic native speakers), stimuli with an accent like their own and the native Hebrew accent, required significantly less phonological information than the other foreign accents. The results support the hypothesis that phonological assimilation works in a similar manner in these two different groups.