Is judgment of random time intervals biased and capacity-limited?

 Recently, random generation of time intervals has been proposed as a procedure to impair executive processing in a dual-task paradigm without substantial interference with phonological and visuo-spatial working memory resources. A fundamental assumption of this procedure is that humans are able to distinguish time sequences on their degree of randomness. The present study tests this assumption. To this end, non-biased, repetition-biased, alternation-biased sequences and repetitive rhythms were judged under conditions of higher or lower executive load. In Exp. 1, load depended on the presentation speed, while in Exp. 2, a dual-task condition was used with either a concurrent number-copying task or an arithmetic task. It was found that the participants could distinguish repetitive rhythms from more or less random sequences, and that both accuracy of this judgment and latency were affected by the concurrent load. The findings are taken as a first indication that random time judgment is capacity-limited. Received: 9 September 1999 / Accepted: 1 October 1999     

A study of temperament and personality in anorexia and bulimia nervosa

Although temperament and personality traits could influence the development and course of eating disorders, only a few studies examined the similarities and differences in personality between anorexia and bulimia nervosa. We compared 72 patients with DSM-IV eating disorders and 30 healthy controls. Dimensions of personality and personality disorders were evaluated with the Eysenck's EPQ, Cloninger's TCI, and the SCID-II questionnaires. The rates of impulsivity and clinical features were evaluated using specific rating scales. A comorbid personality disorder was found in 61.8% of patients with eating disorder. Avoidant personality disorder appeared was relatively common in anorexia nervosa restricting type; borderline personality disorder was most frequent in bulimia nervosa and the binge eating-purging type of anorexia nervosa. From a dimensional perspective, anorexic patients presented high scores in the dimension of persistence. Higher harm avoidance and impulsivity was found in bulimic patients. The overall eating disorders group presented high scores in neuroticism and low scores in self-directedness. Eating disorder patients have heterogeneous features of temperament and personality traits. Cluster C personality disorders seem more common in anorexia nervosa restricting type and impulsive personality features are associated with bulimic symptoms. Impulsivity seems to be a key aspect of temperament of bulimic patients, whereas anorexic symptoms are linked to persistent temperament traits.     

Familial multiple sclerosis with repetitive relapses of manic psychosis in two patients (mother and daughter)

The clinical presentation of multiple sclerosis (MS) with psychiatric symptoms is uncommon but it is believed that MS patients are twice as likely to be afflicted with bipolar disorder as the general population. We report two cases (mother and daughter) of MS presenting with bipolar disorder in the form of recurrent manic psychosis and whose outcome was favourable with neuroleptics and corticosteroids. In both cases we found multiple hypersignal lesions on brain magnetic resonance imaging (MRI), especially in the right frontal lobe where we observed signs of activity. Apart from clinical and radiological concordance, the patients exhibited similar class I HLA alleles and identical class II HLA alleles. We focused discussion on whether there may be a common genetic susceptibility to both illnesses or whether MS caused psychiatric manifestations. The coincidence of psychiatric and neurological symptoms in most relapses supports the second hypothesis.     

Central executive system impairment in traumatic brain injury

The aim of the present study was to identify cognitive functions affected by traumatic brain injury (TBI) and to verify the mechanism underlying cognitive impairment. More precisely, cognitive deficits following TBI can be considered as a consequence of (a) a speed processing deficit, that is a general slowing of perceptual, motor and cognitive subroutines; (b) an impairment of the Central Executive System of working memory (CES).Thirty-seven patients were submitted to a neuropsychological battery, aimed to evaluate different cognitive functions.Results showed severe deficits in speed processing, divided attention,working memory, executive functions and long term memory.Regression analyses, performed to test the two hypotheses, showed that the working memory deficit hypothesis is able to explain divided attention, executive functions and long term memory deficits more than speed processing hypothesis.     

Duration estimation and the phonological loop: Articulatory suppression and irrelevant sounds

Clock-based theories of time estimation propose that clock pulses are accumulated in working memory. Although these theories do not constrain the form of the memory trace, evidence reported in the literature suggests that active manipulation of a verbal trace may be involved. Four experiments are reported in which participants reproduced or verbally estimated short durations (up to a few seconds) either in a single-task condition or in a condition with a phonological load. Experiments 1, 2 and 4 showed that both interval reproduction and verbal estimation were impaired under concurrent articulatory suppression in comparison to a timing only control condition. Neither irrelevant speech (Experiments 1-3) nor irrelevant tones and music (Experiment 3) impaired timing performance. These findings are taken to show that time estimation is mediated by phonological working memory and the involvement of an active articulatory rehearsal process.     

The effect of spatial-frequency filtering on the visual processing of global structure

In three experiments we measured reaction times (RTs) and error rates in identifying the global structure of spatially filtered stimuli whose spatial-frequency content was selected by means of three types of 2-D isotropic filters (Butterworth of order 2, Butterworth of order 10, and a filters with total or partial Gaussian spectral profile). In each experiment, low-pass (LP), bandpass (BP), and high-pass (HP) filtered stimuli, with nine centre or cut-off spatial frequencies, were used. Irrespective of the type of filter, the experimental results showed that: (a) RTs to stimuli with low spatial frequencies were shorter than those to stimuli with medium or high spatial frequencies, (b) RTs to LP filtered stimuli were nearly constant, but they increased in a nonmonotonic way with the filter centre spatial frequency in BP filtered stimuli and with the filter cut-off frequency in HP filtered stimuli, and (c) the identification of the global pattern occurred with all visible stimuli used, including BP and HP images without low spatial frequencies. To remove the possible influence of the energy, a fourth experiment was conducted with Gaussian filtered stimuli of equal contrast power (c(rms) = 0.065). Similar results to those described above were found for stimuli with spatial-frequency content higher than 2 cycles deg(-1). A model of isotropic first-order visual channels collecting the stimulus spectral energy in all orientations explains the RT data. A subsequent second-order nonlinear amplitude demodulation process, applied to the output of the most energetic first-order channel, could explain the perception of global structure of each spatially filtered stimulus, including images lacking low spatial frequencies.     

Dancing shapes: a comparison of luminance-induced distortions

We present an illusory display in which a grid of outlined squares is positioned in front of a moving luminance gradient. Observers perceive a strong, illusory, 'wavelike' motion of the superimposed squares. We compared luminance effects on dynamic and static aspects of this illusion. The dynamic aspect was investigated by means of a temporal gradient, which induced an illusory pulsing of the outlined squares. The static aspect was investigated in two different ways. In one experiment, the outlined squares were positioned on a spatial gradient, which caused the squares to look like trapezoid shapes. In another experiment, the squares were positioned on different luminance fields, which affected their apparent size. In all experiments, luminance settings were the same, and observers were asked to indicate the direction and strength of the induced distortions. The overall results show large agreements between the dynamic distortion and the first-mentioned static distortion, whereas different tendencies emerged for the second static distortion. In a second series of experiments, we examined these distortions for various ranges of the luminance gradient and for border gradients as well. On the basis of these data, we explored how the directions of the perceived distortions of the single-gradient displays examined in this paper could be related to each other.     

Surface assignment modulates object formation for visual short-term memory

Recent results have suggested that the operational units of visual short-term memory (VSTM) are whole objects, rather than features or the total amount of information to be remembered. Here, for the first time, the influence of surface assignment on object formation for VSTM was investigated. The observers had to memorize the features of four briefly presented (300 ms) two-part objects, followed by a mask and a cue indicating which object to report on. The experiments contrasted whether there were any apparent depth differences between the two parts of each object, and whether observers had to report on only one or both features of the post-cued target object. Depth differences induced with stereoscopic disparity, and with a pictorial depth cue (simple interposition of object features), interfered strongly with performance when both features of an object needed to be memorized, but aided performance when only a single feature needed to be remembered. Furthermore, there was considerable within-feature interference consistent with some previous findings, but contradicting others. The potential implications for conceptions of VSTM are discussed in the light of two hypothesized stages: an early feature-based stage, as well as a higher-level object-based stage where the depth manipulations exert their effects. The results argue for a strong modulatory influence of surface assignment on object formation for a VSTM task.     

Sexuality and Exercise Motivations: Are Gay Men and Heterosexual Women Most Likely to be Motivated by Concern About Weight and Appearance?

This study was designed to investigate the relationship between sexuality and exercise motivations in 93 British bar staff. Participants who self-identified as heterosexual, gay, or lesbian completed the revised version of the Exercise Motivations Inventory and reported exercise frequency. Heterosexual men scored lower on appearance motives than did heterosexual women and gay men, higher on enjoyment motives than did gay men, and higher on competition motives than did women and gay men. Men were significantly less likely than women to be motivated by weight management. Heterosexual men also reported exercising significantly more frequently than the other three groups. Suggestions for targeted exercise promotion initiatives are discussed.     

Qualitative differences between implicit and explicit sequence learning

Four experiments investigate the differences between implicit and explicit sequence learning concerning their resilience to structural and superficial task changes. A superficial change that embedded the SRT task in the context of a selection task, while maintaining the sequence, did selectively hinder the expression of implicit learning. In contrast, a manipulation that maintained the task surface, but decreased the sequence validity, affected the expression of learning specifically when it was explicit. These results are discussed in the context of a dynamic framework (Cleeremans & Jiménez, 2002), which assumes that implicit knowledge is specially affected by contextual factors and that, as knowledge becomes explicit, it allows for the development of relevant metaknowledge that modulates the expression of explicit knowledge.