Memory for symmetry and perceptual binding in patients with schizophrenia

The present study investigated the use of perceptual binding processes in schizophrenic (SC) patients and matched healthy controls, by examining their performance on the recall of symmetrical (vertical, horizontal and diagonal) and asymmetrical patterns varying in length between 2 and 9 items. The results showed that, although SC patients were less accurate than controls in all conditions, both groups recalled symmetrical patterns better than asymmetrical ones. The impairment of SC patients was magnified with supra-span symmetrical arrays, and they were more likely to reproduce symmetrical patterns as asymmetrical, particularly at medium and high length levels. Hierarchical regression analyses further indicated that the between-group differences in the recall of supra-span vertical and horizontal arrays, which require a greater involvement of visual pattern processes, remained significant after removing the variance associated with performance on asymmetrical patterns, which primarily reflects intrafigural spatial processes. It is proposed that schizophrenia may be associated with a specific deficit in the formation and retrieval of the global visual images of studied patterns and in the use of the on-line information about the type of symmetry being tested to guide retrieval processes.     

Laterality effects in the spinning dancer illusion: The viewing‐from‐above bias is only part of the story

The ‘silhouette illusion’, representing the silhouette of a female dancer pirouetting about her vertical axis, is a bistable stimulus created by Japanese web designer Nobuyuki Kayahara. Although the dancer can be perceived as spinning either clockwise or counterclockwise, the clockwise rotation is usually preferred. Troje and McAdam (i‐Perception, 2010, 1, 143) showed that this clockwise bias can be attributed to the tendency to assume a viewpoint from above rather than from below, given that the dancer is portrayed from a vantage point that is not perpendicular to the axis of rotation. Here, we tested whether another possible factor contributing to the observers’ interpretation of this bistable stimulus might be the tendency to perceive movements of the right rather than the left foot. We confirmed both the viewing‐from‐above bias and our hypothesis. The bias to perceive movements of the right leg might be a generalization to lower limbs of a perceptual frequency effect already observed for upper limbs. Such a perceptual and attentional bias towards the right hand/foot could account for the greater ability to predict the outcome of sport actions when observing right‐ rather than left‐limbed movements, and thus the left‐handers' and left‐footers' advantage observed in a variety of interactive sports.     

De Finetti coherence and the product law for independent events

Synthese - In an earlier paper the present author proved that de Finetti coherence is preserved under taking products of coherent books on two finite sets of independent events. Conversely, in this...     

A Critique of Victoria S. Harrison’s Internal Realist Approach to Pluralism

Philosophia - Victoria S. Harrison’s theory of internal pluralism approaches religious beliefs in terms of conceptual schemes. To her, this approach has the advantage of preserving core...     

The impact of phantom decoys on choices in cats

Context-dependent choice is an important aspect of decision making. The paper examines context-dependent choice in cats (Felis catus), with particular reference to the effect of local context, on the basis of hypotheses developed in the field of human decision making. Cats were initially confronted with two different feeding options. This binary choice set was later manipulated incorporating a decoy that was better than the available options but ultimately unavailable (a phantom). By means of a within-subjects manipulation of phantom location in the attribute space, the author compared the effects of close and distant phantoms on the final choices. The main finding is that close phantom decoys affected choice behavior of cats by altering the overall share of the available options, leading some animals to reject even some of the available feeding options, and by causing the animals to favor the available option that was more similar to the phantom decoy. No significant effects emerged for phantoms that were far from the alternatives in the attribute space. The strengths of this paper lie in its novel approach and high originality. No other study has used dominating decoys with animals or decoys that are unattainable. This paper provides strong links to the human decision making literature, the presentation of the predictions of a range of different choice models, and the novelty of the application to animals. The use of a phantom decoy is particularly interesting because the phantom cannot actually be chosen, and thus the binary and trinary choice sets both have the very same choices available. Overall, the effect of phantoms is real, interesting and new.     

Value-based accounts of normative powers and the wishful thinking objection

Philosophical Studies - Normative powers like promising allow agents to effect changes to their reasons, permissions and rights by the means of communicative actions whose function is to effect...     

Characteristics and reversibility of dementia in Normal Pressure Hydrocephalus

Studies of the cognitive outcome after shunt insertion for treatment of Normal Pressure Hydrocephalus have reported widely mixed results. We prospectively studied performance of 60 patients with Normal Pressure Hydrocephalus on a comprehensive battery of neuropsychological tests before and after shunt surgery to determine which cognitive functions improve with shunt insertion. We also administered a subset of cognitive tests before and after temporary controlled drainage of cerebrospinal fluid to determine if change on this brief subset of tests after drainage could predict which patients would show cognitive improvement three to six months after shunt insertion. There was a significant improvement in learning, retention, and delayed recall of verbal memory three to six months after surgery (using paired t-tests). The majority (74%) of patients showed significant improvement (by at least one standard deviation) on at least one of the memory tests. Absence of improvement on verbal memory after temporary drainage of cerebrospinal fluid had a high negative predictive value for improvement on memory tests at 3-6 months after surgery (96%; p=0.0005). Also, the magnitude of improvement from Baseline to Post-Drainage on few specific tests of learning and recall significantly predicted the magnitude of improvement after shunt surgery on the same tests (r2=0.32-0.58; p=0.04-0.001). Results indicate that testing before and after temporary drainage may be useful in predicting which patients are less likely to improve in memory with shunting.