Differential K theory: The sociobiology of individual and group differences

Differential K Theory is proposed to help systematize individual and group differences in life histories, social behaviour and physiological functioning. K refers to one end of a continuum of reproductive strategies organisms can adopt, characterized by the production of very few offspring with a large investment of energy in each. At the opposite extreme is the r-strategy in which organisms produce a large number of offspring but invest little energy in any one. Between-species comparisons demonstrate that these reproductive strategies correlate with a variety of life history traits including: litter size, birth-spacing, parental care, infant mortality, developmental precocity, life span, intelligence, social organization and altruism. As a species, humans are at the K end of the continuum. Some people, however, are postulated to be more K than others. The more K a person is, the more likely he or she is to come from a smaller sized family, with a greater spacing of births, a lower incidence of DZ twinning, and more intensive parental care. Moreover, he or she will tend to be intelligent, altruistic, law-abiding, behaviourally restrained, maturationally delayed, lower in sex drive and longer lived. Thus diverse organismic characteristics, not otherwise relatable, are presumed to covary along the K dimension. Group differences are also hypothesized, such that, in terms of K: higher socio-economic > lower socio-economic; and Mongoloids > Caucasoids > Negroids.     

Seeking urgent pediatric treatment: factors contributing to frequency, delay, and appropriateness

The present study explored the factors that contribute to mothers' decisions to seek urgent medical attention for their children when symptoms are not of a traumatic nature. One hundred mothers seeking treatment for their children at a prepaid clinic completed a questionnaire eliciting their expectations regarding the course of their children's problems, seriousness of the problems, perceived responsibility for the symptoms, and extent to which a variety of factors contributed to their decisions to seek treatment. Demographic data and information about each child's symptoms and medical history were also obtained. Four major "reasons for seeking treatment" factors were identified: family history of the presenting complaint, worry regarding the symptoms, situational variables, and the extent of the child's illness behavior. The appropriateness of the visit, delay in seeking treatment, and frequency of mothers' use of the pediatric clinic were predicted by the nature of the presenting symptoms (particularly the presence of fever), the ages of the mother and child, and two of the reasons for seeking treatment factors (i.e., family history and child's illness behavior). The present study suggests that mothers pay more attention to presenting symptoms and to the children's behavior than to psychosocial stressors in deciding to seek urgent care.     

Selective cardiovascular effects of stress and cigarette smoking in young women

In an earlier study, we found that men who smoked a cigarette and then engaged in a mildly stressful activity (video game) evidenced pronounced increases in heart rate and blood pressure, which were approximately equal to the sum of the effects produced by either smoking alone or stress alone. In the present study, a 2 (smoke vs. sham smoke) X 2 (stress vs. no stress) factorial design was used to evaluate the impact of stress and smoking on the cardiovascular responses of young women. The results revealed that the combination of stress and cigarette smoking produced blood pressure and heart rate responses that were larger than the additive effects of smoking and stress taken separately.     

Co-occurrent use of cigarettes, alcohol, and coffee in healthy, community-living men and women

Previous studies have examined intra-individual aggregation in the use of cigarettes, alcohol, and coffee by examining the co-occurrent use of any pair of these three substances. A recent literature review failed to find a single investigation that studied use of all three in the same sample. In the present study, co-occurrent use of all three of these substances was examined in crossvalidated subsamples of 226 male and 245 female healthy, community-living, middle-class Americans. A log-linear analysis was used to compare the proportion of smokers, ex-smokers, and nonsmokers categorized as users of more or less amounts of coffee and alcohol. Although most of the intercorrelations were not strong, the results indicate that for both sexes, smokers and ex-smokers were more likely than nonsmokers to drink greater amounts of alcohol and coffee. Furthermore, for smokers, ex-smokers, and nonsmokers, a majority of individuals who reported drinking more alcohol also reported drinking more coffee. Interestingly, the coffee and alcohol consumption levels of ex-smokers resembled those of smokers more than those of nonsmokers. Also, ex-smokers reported drinking more wine and decaffeinated coffee than either smokers or nonsmokers. Finally, the number of cigarettes smoked per day (daily quantity) was positively related to total alcohol and coffee consumption in men, but not in women. Further studies are recommended to examine the role of individual differences in the development, maintenance, and modification of these three appetitive habits and their co-occurrence.     

Chimpanzee (Pan troglodytes) spatial problem solving with the use of mirrors and televised equivalents of mirrors

Two adult male chimpanzees reached through a hole in the wall of their home cage and, by tracking the images of their hands and of an otherwise hidden target object in a mirror or closed-circuit television picture, moved their hands in whichever direction was necessary to make contact with the target object. They discriminated between live video images and tapes and performed effectively when the target objects were presented in novel locations and when the video picture was presented at random in different orientations. There was thus no consistent relation between the location of images on the monitor and the location of their real-world counterparts. Comparable performances in monkeys and nonprimates seem unlikely.     

Responsiveness to estrous chemostimuli in male rats (Rattus norvegicus) of different ages

Previous findings indicate that Norway rats (Rattus norvegicus) respond differentially to estrous chemostimuli in early infancy and that adult male sexual responsiveness to such chemostimuli depends on infantile experience with suckling odors (Fillion & Blass, in press). The development of behavioral responsiveness to estrous chemostimuli in male rats from late infancy to adulthood was examined in this study. Preweanling, adolescent, and adult males were observed for 20 min in the presence of an anesthetized estrous or an anesthetized diestrous female. This was, for adolescent and adult subjects, the first heterosexual encounter since weaning. Rats in each age-group responded differentially according to female state, but in distinct, age-related ways. Preweanling spent more time investigating the female's body if she was estrous. Adults expressed the same affinity but by more focused investigation directed perivaginally. Adolescents showed no female-directed bias but groomed themselves more if the female was estrous. These data identify developmental continuities and discontinuities in male rat behavior toward sexually receptive females.