Kin Relationships and the Caregiving Biases of Grandparents, Aunts, and Uncles : A Two-Generational Questionnaire Study.

Paternity certainty and matrilineal family ties have been used to explain the asymmetric caregiving of grandparents and aunts and uncles. The proximate mechanisms underlying biased kin investment, however, remain unclear. A central question of the study presented here was whether the parent-kin relationship is an important link in the caregiving. In a two-generational questionnaire study, we asked subjects to estimate the intensity of their relationships to parents, grandparents, aunts, and uncles (emotional closeness, investment received in childhood). In addition, the subjects' parents rated their emotional closeness to their parents and siblings. We found that the parent-kin relationship was closely linked to the relatives' child care and could partly explain asymmetric caregiving. Maternal aunts played a special role as caregivers. Especially the mother's younger or last-born sister cared intensively for nieces and nephews, regardless of her closeness to the subjects' mother.

Tonic and phasic processes in the acute effects of alcohol.

This article presents a novel method for measuring the acute effects of alcohol. One hundred twenty nonproblem drinkers aged 21-28 participated in 3 alcohol administration sessions that produced peak blood alcohol concentrations (BACs) near .09 g%. Subjective intoxication ratings were taken at multiple points across rising and falling BACs. Mathematical modeling techniques decomposed intoxication ratings into a tonic component sensitive to BAC level and a phasic component sensitive to BAC rate of change. This model provided a good fit to observed data. Tonic and phasic gain parameters showed high repeatability across sessions. The average phasic gain parameter was about 4 times larger than the average tonic gain parameter, indicating that subjective intoxication is usually more affected by BAC change than by BAC level. The associations of drinking practices with tonic and phasic gain parameters varied by gender and family history of alcoholism. Tonic-phasic modeling allows individual and group differences in the acute effects of alcohol to be studied as time-dynamic processes.

Tonic, phasic, and integrator components of psychophysical responses to topical capsaicin account for differences of location and sex.

UNLABELLED: We reanalyze data of Frot et al on sex and location differences in the pain response to topical capsaicin using a dynamic model developed from responses to oral capsaicin. This model considers the pain response as the sum of 3 underlying component processes: a phasic component, a tonic component, and an integrator component. Sex differences in response to stimulation of both the cheek and ankle could be accounted for by a greater gain in the tonic mechanism. Responses to ankle stimulation showed a greater integrator component than responses to cheek stimulation, a negligible phasic component, and required a time delay. This analysis demonstrates that the model is applicable to responses to stimuli outside the oral cavity and that it can explain differences due to location and sex, in addition to explaining sensitization, desensitization, and individual differences in earlier studies. Application of this model in future genetic studies, for instance, would be more appropriate than the use of the peak response or the response at an arbitrarily determined time. PERSPECTIVE: This dynamic model provides insight into individual differences in sensitivity to vallinoid receptor-activating compounds including capsaicin, and it may be useful for the identification of subgroups of patients with differential responsiveness to therapeutic topical capsaicin. A similarly derived model might prove useful for the analysis of development of chronic pain.

Three distinct categories of time course of pain produced by oral capsaicin.

UNLABELLED: Humans vary in oral pain tolerance. Our earlier studies noted that the responses of subjects show 1 of 3 qualitative response patterns to a single oral capsaicin concentration, which we termed a tonic pattern (level detection response), a phasic pattern (change detection response), and an integrator pattern (cumulative irritation) response. These patterns were modeled quantitatively as the sum of 3 underlying processes. Two time-varying capsaicin stimulus profiles were designed from the quantitative model. In the ascending step paradigm, 30 ppm capsaicin was presented to 42 subjects for 15 minutes, followed immediately and without explanation by 300 ppm capsaicin for 25 minutes. In the descending step paradigm, 300 ppm capsaicin was presented to 36 other subjects for 24 minutes, followed by 10 ppm for 22 minutes. Subjective burn was rated at 1 minute and then at 3-minute intervals throughout the presentation. Fuzzy cluster analysis identified 3 distinct response phenotypes in each paradigm, corresponding to level detection, change detection, and cumulative irritation response patterns identified previously. Discriminant functions permitted classification of these phenotypes from the response patterns. Thus, these paradigms provide the first quantitative phenotypic description of distinct oral pain responses to a common irritant, capsaicin. PERSPECTIVE: This study examined the time-dependent behavior of pain produced by oral application of capsaicin. Three distinct temporal response phenotypes were identified objectively: level detection, change detection, and cumulative irritation detection. These time-dependent analyses provide a new dimension to understanding individual differences in pain sensation in clinical settings.

Matrilateral biases in the investment of aunts and uncles : Replication in a population presumed to have high paternity certainty.

Gaulin, McBurney, and Brakeman-Wartell (1997) found that college students reported both matrilateral and sex biases in the investment of aunts and uncles (aunts invested more than uncles). They interpreted the matrilateral bias as a consequence of paternity uncertainty. We replicated that study with Orthodox Jewish college students, selected because they come from a population we presume to have higher paternity certainty than the general population. The Orthodox sample also showed matrilateral and sex biases. Comparing the two data sets, the Orthodox sample reported more investment, and slightly less matrilateral and sex biases, but the differences were not statistically significant. We did find an interaction between sex of relative and group membership, resulting from greater investment by Orthodox uncles. We interpret the results as reflecting the operation of a facultative investment mechanism whose upper limit is tuned to the maximum levels of paternity certainty found in ancestral environments. Lack of a difference in matrilateral bias between groups may result from levels of paternity certainty near to, or above, that maximum in both groups.

A heuristic model of sensory adaptation.

Adaptation is a universal process in organisms as diverse as bacteria and humans, and across the various senses. This article proposes a simple, heuristic, mathematical model containing tonic and phasic processes. The model demonstrates properties not commonly associated with adaptation, such as increased sensitivity to changes, range shifting, and phase lead. Changes in only four parameters permit the model to predict empirical psychophysical data from different senses. The relatively prolonged time courses of responses to oral and topical capsaicin are used to illustrate and validate this mathematical modeling approach for different stimulus profiles. Other examples of phenomena elucidated by this modeling approach include the time courses of taste sensation, brightness perception, loudness perception, cross-adaptation to oral irritants, and cutaneous mechanoreception. It also predicts such apparently unrelated phenomena as perceived alcohol intoxication, habituation, and drug tolerance. Because the integration of phasic and tonic components is a conservative, highly efficacious solution to a ubiquitous biological challenge, sensory adaptation is seen as an evolutionary adaptation, and as a prominent feature of Mother Nature's small bag of tricks.

Temporal interactions between oral irritants: piperine, zingerone, and capsaicin.

Sequential presentation of 2 irritants may produce cross-sensitization or cross-adaptation effects upon introduction of the second irritant. In Experiment 1, subjects were given either 34 min of stimulation with zingerone, capsaicin, or piperine or one of those irritants for 23 min followed by blanks for 23 min. In Experiment 2, subjects received one irritant for 23-min irritants, followed immediately by another for 23 min (piperine --> zingerone, piperine --> capsaicin, zingerone --> piperine, or zingerone --> capsaicin). Cross-sensitization was observed for the piperine --> zingerone, zingerone --> piperine, and piperine --> capsaicin groups; cross-adaptation was observed for the zingerone --> capsaicin group. Cross-adaptation and cross-sensitization were predicted by adding the independent time courses of the respective irritants, starting the second at the offset of the first. These responses were also predicted by a mathematical model of central processing of primary afferent responses.