Extraction of relief from visual motion

We quantified the ability of human subjects to discriminate the relative distance of two points from a slanted plane when viewing the projected velocities of this scene (orthographic projection). The relative distance from a plane (called relief) is a 3-D property that is invariant under linear (affine) transformations. As such, relief canin principle be extracted from the instantaneous projected velocity field; a metric representation, which requires the extraction of visual acceleration, is not required. The stimulus consisted of a slanted planeP (specified by three points) and two pointsQ ₁ andQ ₂ that are non-coplanar withP. This configuration of points oscillated rigidly around the vertical axis. We have measured thesystematic error andaccuracy with which human subjects estimate the relative distance of pointsQ ₁ andQ ₂ from planeP as a function of the slant of_P. The systematic error varies with slant: it is low for small slant values, reaches a maximum for medium slant values, and drops again for high slant values. The accuracy covaries with the systematic error and is thus high for small and large slant values and low for medium slant values. These results are successfully modeled by a simple relief-from-motion computation based on local estimates of projected velocities. The data are well predicted by assuming (1) a measurement error in velocity estimation that varies proportionally to velocity (Weber’s law) and (2) an eccentricity-dependent underestimation of velocity.     

Phonological sensitivity and the acquisition of new words in children

Two studies are reported which aimed to examine the relationship between phonological sensitivity and the acquisition of new words that systematically differed in the familiarity of their sound structures. In the first study measures of phonological sensitivity, phonological short-term memory, vocabulary, and nonverbal ability were administered to forty-one 5-year-old children. Phonological sensitivity was related to the paired-associate learning of phonologically unfamiliar words, but not to the learning of familiar words. In the second study a group of 14 nonreading 5-year-old children received phonological sensitivity training. A control group was trained in semantic categorization. After the training, the phonological sensitivity group did perform better on measures of letter knowledge and phonological sensitivity (rhyme and first-sound categorization) and appeared to learn phonologically unfamiliar words more easily. The findings of both studies suggest that phonological sensitivity can support the acquisition of novel words.     

Difference scores: A caveat illustrated with neuropsychological measures

Relationships among preferred minus non-preferred hand difference scores from four neuropsychological sensorimotor tests were evaluated in Community (N= 121), Prison Inmate (N = 350), and Psychiatric Inpatient (N = 398) samples. Across the three samples, the average absolute off-diagonal correlations among the four difference scores ranged from .07 to .13, and the squared multiple correlations (used to predict any difference score from the other three) did not exceed .07. Based on the determinant of the correlation matrix (i.e., |R|), the null hypothesis of complete independence was rejected in only the Prison Inmate sample (p < .001), however, departure from the null hypothesis was negligible (i.e., |R| = .94, expected value under the null = .98). Preferred/non-preferred hand ratio scores were very highly correlated with the difference scores and consequently analyses of the ratio scores yielded results that were comparable to those obtained for the difference scores. Results indicate that the four difference scores or four ratio scores measure little in common and therefore cannot corroborate each other. In general, it would be prudent to exercise considerable caution when using difference scores or ratio scores obtained from non-independent measures, either singly or in combination.     

C-reactive protein polymorphisms are associated with the cortisol awakening response in basal conditions in human subjects

Cortisol affects the acute-phase response, but it is unknown whether C-reactive protein (CRP), an acute-phase reactant, also affects hypothalamus?pituitary?adrenal axis activity. In the present study, associations were explored between CRP haplotypes with plasma CRP concentrations and basal salivary cortisol level. We included 266 physically healthy Caucasian subjects (103 females and 163 males) aged between 18 and 65 years of whom 94 had a psychiatric disorder in a genetic association study. Six tag single-nucleotide polymorphisms capturing the common genetic variation of the CRP gene were genotyped (i.e. rs2808628, rs2808630, rs1205, rs1800947, rs1417938, and rs3091244) to yield common CRP haplotypes. Plasma CRP concentrations, the salivary cortisol awakening response (CAR) (0, 30, 45, and 60?min after awakening), and the diurnal cortisol decline (11:00, 15:00, 19:00, and 23:00 h) were assessed for 2 days. rs2808628, rs1205, rs1417938, and rs3091244 showed expected associations not only with CRP concentrations, but also with salivary cortisol levels during the CAR. Five well-characterized CRP haplotypes were arranged in ascending order according to increasing CRP levels. There was an inverse linear association between CRP haplotypes and cortisol levels during the CAR, but no association with the diurnal cortisol decline. Hence, genetic variants in the CRP gene that are associated with lifetime plasma CRP levels were also associated with salivary cortisol levels after awakening, in basal, non-inflammatory conditions.     

Financial problems and psychological distress: Investigating reciprocal effects among business owners

Building on conservation of resources theory and the dynamic equilibrium model, this three‐wave longitudinal study among 260 Dutch agricultural business owners (1‐year time intervals) investigated reciprocal relationships between the financial situation of the business and psychological distress. Results of structural equation modelling analyses revealed a negative spiral of farm decline, in which psychological variables played a key role. Experiencing financial problems predicted psychological distress, and acted as a self‐fulfilling prophecy by strengthening intentions to quit the business, which predicted a deterioration of the objective financial situation of the business 1 year later. Moreover, farmers experiencing more psychological distress were more likely to get caught in this negative spiral than business owners with better mental health, because they experienced more financial problems, irrespective of their objective financial situation. Long‐term psychological distress rather than temporary fluctuations in distress levels accounted for this effect.     

The power distance reduction hypothesis on a level of reality

An experiment and a replication were conducted, testing the hypothesis that the smaller the actual power distance between a subject and a more powerful other, the stronger the tendency to reduce the power distance between them. Power distance was created by placing the subject in a group of three people plus a supervisor. In the condition of large power distance, the three workers had identical functions. Small power distance was induced by placing the subject at an intermediary power level, above the two workers, but below the supervisor. Two other conditions of small power distance were manipulated in order to assess the effects of the timing of power promotion and the perception of the promotion as caused by the subject's task competence. During the course of the experiment, the supervisor left unexpectedly and the subject had the option of taking over the supervisory role or letting one of his co-workers assume it. In the first experiment, subjects who were at a large power distance chose to replace the supervisor significantly less frequently than subjects in the three small power-distance conditions. The small power-distance conditions did not differ from each other. The replication with two small power-distances conditions produced the same results. Both experiments took place in a natural setting.     

Velocity constancy in a virtual reality environment

During everyday life the brain is continuously integrating multiple perceptual cues in order to allow us to make decisions and to guide our actions. In this study we have used a simulated (virtual reality--VR) visual environment to investigate how cues to speed judgments are integrated. There are two sources that could be used to provide signals for velocity constancy: temporal-frequency or distance cues. However, evidence from most psychophysical studies favours temporal-frequency cues. Here we report that two depth cues that provide a relative object--object distance--disparity and motion parallax--can provide a significant input to velocity-constancy judgments, particularly when combined. This result indicates that the second mechanism can also play a significant role in generating velocity constancy. Furthermore, we show that cognitive factors, such as familiar size, can influence the perception of object speed. The results suggest that both low-level cues to spatiotemporal structure and depth, and high-level cues, such as object familiarity, are integrated by the brain during velocity estimation in real-world viewing.     

Seemingly anomalous full scale IQ scores on the WAIS-III and the WISC-III

The Canadian and American WISC-III and the American WAIS-III standardization data were used to investigate the prevalence of “seemingly anomalous” Full Scale IQ (FSIQ) scores for all possible Verbal and Performance sums of scale score combinations. It was found that 6% of FSIQ scores in these three samples were seemingly anomalous (i.e., fell outside of their associated VIQ/PIQ intervals). Interestingly, the anomalous FSIQ scores were more prevalent at the extremes of the FSIQ distribution, and did not occur when the VIQ/PIQ interval was greater than 12. Additionally, anomalous FSIQ scores were generally further from the center of the FSIQ distribution than were the associated VIQ and PIQ scores. Also, when the VIQ/PIQ interval contained FSIQ (the non-anomalous case), FSIQ tended to be located distally in the half-segment of the VIQ/PIQ interval furthest from the center of the FSIQ distribution. A statistical explanation for the findings is provided. Portions of this paper were presented March 3, 2000 at the 14th Annual Joseph R. Royce Research Conference, Department of Psychology, University of Alberta, Edmonton, Alberta. An erratum to this article is available at .