Åke Hellström

Comparison is not just subtraction: Effects of time- and space-order on subjective stimulus difference

In five experiments, participants made comparative judgments of paired successive or simultaneous stimuli. Time- or space-order errors were obtained, which varied with the interstimulus interval (ISI) or stimulus duration, as well as with the stimulus level. The results, in terms of scaled subjective differences, are well described by Hellström’s (1979) sensation-weighting model. With successive presentation, in comparisons of line length and tone loudness, the first stimulus had the greater weight in determining the subjective difference for short ISIs, the second for longer ISIs. In comparisons of duration (auditory and visual), the second stimulus had the greater weight. For simultaneously presented line lengths, the left stimulus had the greater weight.

Time errors are perceptual

SummaryMethods for the measurement of time-errors (TEs) in the comparison of successive stimulus magnitudes are discussed. Combining a Thurstonian scaling method with the assumption of a fixed subjective width of the “equal” category, independent of stimulus level, a ratio scale for subjective differences within pairs of successive stimuli is derived. In a tone duration comparison experiment, with the TE defined in the terms of these subjective duration differences, data from four experimental groups were compared, the groups using different modes of judging and responding. Only minor effects of this factor were found, and hence it is concluded that the TE is a true perceptual phenomenon rather than an effect of response bias, criterion bias, or mediating verbal responses to the absolute level of stimulation. The quantitative results are interpreted in terms of a general model for the comparison of successive stimuli, employing the concepts of adaptation and differential weighting of sensation magnitudes.

Impaired verb fluency: A sign of mild cognitive impairment

We assessed verb fluency vs. noun and letter-based fluency in 199 subjects referred for cognitive complaints including Subjective Cognitive Impairment, Mild Cognitive Impairment, and Alzheimers disease. ANCOVAs and factor analyses identified verb, noun, and letter-based fluency as distinct tasks. Verb fluency performance in Mild Cognitive Impairment differed significantly from Subjective Cognitive Impairment and Alzheimers disease. Reduced verb fluency thus appears to be a linguistic marker for incipient dementia. One possibility is that the verb fluency deficit in Mild Cognitive Impairment results from degenerative processes known to occur in the parahippocampal region.

Facets on the psychopathy checklist screening version and instrumental violence in forensic psychiatric patients

BACKGROUND There is a recognised relationship between psychopathy and instrumental violence, but not all violence by people who meet the criteria for psychopathy is instrumental. AIMS Our aims were to compare offence types among forensic psychiatric patients with and without the Psychopathy Checklist: Screening Version (PCL: SV) criteria for psychopathy. Our specific questions were whether factor 1 - the interpersonal affective dimension - was related to instrumentality and on severity of the violent crime. Our hypothesis was that the relationship between psychopathy and instrumental violence would be dependent on the severity of the violent crime. METHODS Sixty-five male patients at the forensic psychiatric hospital in Sundsvall, all with a violent criminal history, were assessed for psychopathy through interview and records using the PCL: SV. Severity and the instrumentality of their previous violence were coded using the Cornell coding guide for violent incidents. RESULTS The interpersonal features of psychopathy (the interpersonal facet), and only the interpersonal features were significantly associated with instrumentality and severity of violence. Instrumentality was also significantly related to the severity of the violence, independent of psychopathy score. CONCLUSIONS The results indicated that, at least among forensic psychiatric patients, planning is more likely than not with respect to serious crimes. The specific link between interpersonal features of psychopathy and instrumental and severe violence suggests potential clinical value in recognising subtypes of psychopathy.

Sensation weighting in comparison and discrimination of heaviness

Participants lifted pairs of successively presented weights and compared them for heaviness, using the constant method with 2, 3, or 6 judgment categories. The standard weight (St) was 100, 200, or 300 g, either roving or fixed within a block. For each St, there were 5 comparison (Co) weights. The lifting orders were St-Co and, with 6 categories, Co-St. Time-order errors were negatively related to St magnitude, particularly with roving St. In terms of Hellströms sensation-weighting theory, this result was accounted for by a smaller weighting coefficient for the first-presented stimulus than for the second. Time-order errors were negative on average, which was explained as the result of this weighting in conjunction with a low position of the reference level because of light background heaviness. With roving St, the dispersion of the subjective intrapair difference increased with St magnitude, providing evidence for Ekmans law (G. Ekman, 1956, 1959).

Tone duration discrimination in Parkinson's disease

Patients with Parkinsons disease (PD) and healthy controls took a computerized test of tone duration discrimination (TDD) using pairs of tones of 0.4-1.6 sec duration, presented at intervals of 0.5-4 sec. In PD patients as well as controls, TDD was impaired by even slight degrees of cognitive deterioration. PD yielded impaired TDD in females, but not in males. This suggests that the dopamine-powered biological clock, which is vulnerable to PD, is more important for the processing of durations in the 1-sec range in women than in men.

Justice Needs a Blindfold: Effects of Gender and Attractiveness on Prison Sentences and Attributions of Personal Characteristics in a Judicial Process

This study examined the effect of gender and facial characteristics of criminal offenders on attributions of crime-relevant traits. The stimulus pictures portrayed women and men of varying attractiveness. Participants were presented with pictures of these female or male faces along with accompanying crime accounts. The crime account described the individual in the picture as a person who had committed one of the following crimes: theft, fraud, drug crime, child molestation, child abuse, or homicide. After reading one case account the participants were asked to evaluate the credibility and other crime-relevant personality traits of the offender. Results showed that female defendants were rated more favourably than were male defendants. Gender worked to the advantage of the female perpetrator. There were also slight tendencies towards more lenient appraisal of the more attractive women.

Cut the coda : Early fluency intervals predict diagnoses

The aim of this study was threefold: (i) to clarify whether letter and category fluency tap different cognitive abilities; (ii) to make diagnostic comparisons and predictions using temporally resolved fluency data; (iii) to challenge and test the widely made assumption that 1-min sum scores are the fluency test measure of choice in the diagnosis of dementia. Scores from six 10-sec intervals of letter and category fluency tests were obtained from 240 participants including cognitive levels ranging from mild subjective cognitive complaints to Alzheimers disease. Factor analysis revealed clearly separate factors corresponding to letter and category fluency. Category fluency was markedly impaired in Alzheimers disease but not in Mild Cognitive Impairment. Only scores from relatively early intervals predicted Alzheimers disease and Mild Cognitive Impairment. The conclusions are (i) letter and category fluency are different tests, category fluency being the best diagnostic predictor; (ii) it would be possible to administer category fluency tests only for 30 sec, because after this point the necessary differential diagnostic information about the patients word fluency capacity has already been gathered.

White matter lesions impair initiation of FAS flow.

Word fluency performance is known to rely on left frontal cortical regions and has also been shown to be affected by lesions in the white matter, which may be seen as white matter hyperintensities (WMH) on magnetic resonance imaging. However, word fluency may be divided into two independent components, initial and late performance, separated in time [J Clin Exp Neuropsychol 1998;20:137–143]. The purpose of the current study was to investigate the relationship between the two components of FAS fluency performance and WMH. Patients varying in degree of memory impairment participated: Alzheimer’s disease, mild cognitive impairment and subjective memory disorder. WMH were rated with the Scheltens scale in the periventricular and deep subcortical areas. Results demonstrated that WMH in this sample of patients may be summarized in two indices according to a principal factor analysis, one anterior factor mainly related to WMH in the frontal lobes and adjacent to ventricles, and a second posterior factor related to parietal and occipital WMH. The initial FAS performance was related to anterior WMH, in particular left frontal or lateral periventricular hyperintensities, whereas the late FAS performance was not related to any index of WMH.

Factors producing and factors not producing time errors: An experiment with loudness comparisons

Pairs of 1-sec, 1,000-Hz tones, with interstimulus intervals of 1.5 sec, were judged by 60 subjects in categories of “louder,” “softer,” and “equal.” The judgments referred to the first tone in the pair for half of the subjects and to the second tone for the other half. Perceived loudness differences were scaled by a Thurstonian method. The SPL of the standard tone alternated between 50 and 70 dB in one experimental series and between 30 and 50 dB in the other. Time errors (TEs) were consistently positive (first tone overestimated relative to second) at the lower SPL and negative at the higher SPL. This “classical” effect of stimulus level on TE was thus shown to depend upon the relative, rather than the absolute, level of stimulation. The judgment mode was of very little consequence, which strongly contradicts TE theories that emphasize response-bias effects. The quantitative results are interpreted in terms of a general successive-comparison model employing the concepts of adaptation and differential weighting of sensation magnitudes.