Variability discrimination in humans and animals: implications for adaptive action

Both humans and animals live in a rich world of events. Some events repeat themselves, whereas others constantly change. The authors propose that discriminating this stability, sameness, and uniformity from change, differentness, and diversity is fundamental to adaptive action. Evidence from many areas of behavioral science indicates that the discrimination of and preference for stimulus variability affects both human and animal action. Recent comparative research with humans and animals illustrates a promising approach to the study of these issues. Discovering and understanding the behavioral and neural processes related to stimulus variability and its consequences for behavior offer distinctive challenges and important new opportunities for psychologists and neuroscientists.     

Effects of varying stimulus size on object recognition in pigeons

The authors investigated the pigeon's ability to generalize object discrimination performance to smaller and larger versions of trained objects. In Experiment 1, they taught pigeons with line drawings of multipart objects and later tested the birds with both larger and smaller drawings. The pigeons exhibited significant generalization to new sizes, although they did show systematic performance decrements as the new size deviated from the original. In Experiment 2, the authors tested both linear and exponential size changes of computer-rendered basic shapes to determine which size transformation produced equivalent performance for size increases and decreases. Performance was more consistent with logarithmic than with linear scaling of size. This finding was supported in Experiment 3. Overall, the experiments suggest that the pigeon encodes size as a feature of objects and that the representation of size is most likely logarithmic.     

Diabetes mellitus as a model of psychosomatic and somatopsychic interrelationships

The article reviews research on the problem of interrelationship between different physical and psychosocial factors in type 1 diabetes mellitus (DM1). The authors consider methodological principles of health-related quality of life (HRQoL) assessment in DM1 patients and stress the need for an integrated biopsychosocial approach to the management of the disease. DM1 is a chronic metabolic disease with an absolute requirement for insulin replacement therapy. The stress-inducing nature of DM1 is associated with its unexpected and dramatic manifestation in juvenile years, life-threatening nature of severe hypo-/hyperglycaemias and long-term complications, with the burden of diabetes self-management, threat of work disability, employment and career problems etc. These features of DM1 increase the likelihood of the development of anxiety and depressive disorders, which, in turn, may negatively influence the course of diabetes and in particular, diabetes self-care. This necessitates early diagnosis of emotional and behavioral disturbances in DM1 using self-report instruments as well as clinical assessment. Evidence suggests that active problem-focused coping behavior and adequate social support promote adherence to diabetes regimes and may act as a buffer against negative effects of the disease on HRQoL in DM1 patients. The core element in the HRQoL structure is personal disease picture (as opposed by objective clinical picture)--the cognitive-affective-behavioral complex reflecting the patient's personal perception of the disease. Examination of the personal disease picture and attitude towards the ailment in DM1 patients may help to improve understanding of the mechanisms of poor adjustment. Problems in disease adjustment can be detected also by diabetes-specific HRQoL assessment. The measures of HRQoL can be applied as screening instruments useful in increasing the effectiveness of patient-provider interactions and diabetes care.     

Associative symmetry in the pigeon after successive matching-to-sample training

If an organism is explicitly taught an A→B association, then might it also spontaneously learn the symmetrical B→A association? Little evidence attests to such “associative symmetry” in nonhuman animals. We report for the first time a clear case of associative symmetry in the pigeon. Experiment 1 used a successive go/no go matching‐to‐sample procedure, which showed all of the training and testing stimuli in one location and intermixed arbitrary and identity matching trials. We found symmetrical responding that was as robust during testing (B→A) as during training (A→B). In Experiment 2, we trained different pigeons using only arbitrary matching trials before symmetry testing. No symmetrical responding was found. In Experiment 3, we trained other pigeons with only arbitrary matching trials and then tested for symmetry. When these pigeons, too, did not exhibit symmetrical responding, we retrained them with intermixed identity and arbitrary matching trials. Less robust symmetrical responding was obtained here than in Experiment 1. Collectively, these results suggest that identity matching may have to be learned concurrently with arbitrary matching from the outset of training for symmetry to emerge.     

Why people engage in parasuicide: a cross-cultural study of intentions

Information obtained at interview from 1,646 parasuicide patients in 14 regions in 13 European countries participating in the WHO/EURO Multicentre Study on Suicidal Behaviour was used to study self-reported intentions involved in parasuicide. Comparisons were made across cultures, genders, and age groups. Although some statistically significant differences were found, the effect sizes were very small. The main finding from this study is thus that parasuicide patients in different countries tend to indicate that similar types of intentions are involved in their acts of parasuicide, and that the intentions do not vary greatly with gender or age. The hypothesis that rates of suicide and parasuicide vary between regions with the frequency with which suicidal intention is indicated by the patients was also tested, but was supported only for women and in relation to national suicide rates. The findings from this study are likely to be generalizable to other settings and have implications for clinical practice.     

Richer color experience in observers with multiple photopigment opsin genes

Traditional color vision theory posits that three types of retinal photopigments transduce light into a trivariate neural color code, thereby explaining color-matching behaviors. This principle of trichromacy is in need of reexamination in view of molecular genetics results suggesting that a substantial percentage of women possess more than three classes of retinal photopigments. At issue is the question of whether four-photopigment retinas necessarily yield trichromatic color perception. In the present paper, we review results and theory underlying the accepted photoreceptor-based model of trichromacy. A review of the psychological literature shows that gender-linked differences in color perception warrant further investigation of retinal photopigment classes and color perception relations. We use genetic analyses to examine an important position in the gene sequence, and we empirically assess and compare the color perception of individuals possessing more than three retinal photopigment genes with those possessing fewer retinal photopigment genes. Women with four-photopigment genotypes are found to perceive significantly more chromatic appearances in comparison with either male or female trichromat controls. We provide a rationale for this previously undetected finding and discuss implications for theories of color perception and gender differences in color behavior.