Introduction: Exploring the Relationships Among Aging,Ethnicity, and Family Dementia Caregiving

Culture, Medicine, and Psychiatry -     

Kin selection,species richness and community

Can evolutionary and ecological dynamics operating at one level of the biological hierarchy affect the dynamics and structure at other levels? In social insects, strong hostility towards unrelated individuals can evolve as a kin-selected counter-adaptation to intraspecific social parasitism. This aggression in turn might cause intraspecific competition to predominate over interspecific competition, permitting coexistence with other social insect species. In other words, kin selection—a form of intra-population dynamics—might enhance the species richness of the community, a higher-level structure. The converse effect, from higher to lower levels, might also operate, whereby strong interspecific competition may limit the evolution of selfish individual traits. If the latter effect were to prove more important, it would challenge the common view that intra-population dynamics (via individual or gene selection) is the main driver of evolution.     

Synchronization of Ultradian Rhythms of Activity in Young Japanese Quail: Effect of Kin Relationships

Synchronization of activity cycles is common in coveys of gallinaceous birds, which usually include a dozen chicks at birth. To study this synchronization more precisely, we recorded the ultradian rhythms of activity of seven groups of young Japanese quail reared in the laboratory, without brooding females. Four groups included only kin-related birds (K1-K4), two mixed groups consisted of associated chicks from two families (M1 and M2 groups), and the seventh group (NK group) included only non-kin chicks. Numbers of chicks in a group varied from eight to 14, depending on the group. They were observed twice during their two first weeks of life (day 3 and day 10) and all activities were recorded by scan sampling. An ultradian rhythm of activity, with a period less than 20 minutes, was found. This period varied among quail families. All chick groups were globally synchronized, except group M2 on day 3. Inter-individual levels of synchronization were calculated. Spearman rank correlation coefficients of the non-kin chicks were significantly lower than those of kin-related chicks. This was especially clear on day 3. Survival of newborn quails is linked to their presence within a covey or a group. Their survival, as well that of their brothers and sisters, may be enhanced by an ability to synchronize with kin better than with non-kin chicks.     

Kin selection,kin avoidance and correlated strategies

Summary Kin selection of correlated strategies is examined for both weak and strong altruism under simple haploid inheritance. While kin assortment enhances the range of evolutionary stability for (strongly altruistic) correlated strategies (defined herein), kin avoidance is possible under a weakly altruistic correlated strategy. When social competition induces role assignments of variable fitness, group mates may prefer association with non-relatives. Even when group life is mandatory, an individual may accept the risk of abandonment (and reproductive death) rather then associate with kin: a competitive superior may behave altruistically by permitting competitively inferior kin to emigrate. Thus, kin selection and social competition are not necessarily mutually supportive processes within groups. I conclude by interpreting dominance as a strongly altruistic correlated strategy in two social hymenopteran contexts.     

Kin recognition and the evolution of altruism

In 1964, Hamilton formalized the idea of kin selection to explain the evolution of altruistic behaviours. Since then, numerous examples from a diverse array of taxa have shown that seemingly altruistic actions towards close relatives are a common phenomenon. Although many species use kin recognition to direct altruistic behaviours preferentially towards relatives, this important aspect of social biology is less well understood theoretically. I extend Hamilton's classic work by defining the conditions for the evolution of kin-directed altruism when recognizers are permitted to make acceptance (type I) and rejection (type II) errors in the identification of social partners with respect to kinship. The effect of errors in recognition on the evolution of kin-directed altruism depends on whether the population initially consists of unconditional altruists or non-altruists (i.e. alternative forms of non-recognizers). Factors affecting the level of these error rates themselves, their evolution and their long-term stability are discussed.     

Kin selection and the evolution of virulence

Social interactions between conspecific parasites are partly dependent on the relatedness of interacting parasites (kin selection), which, in turn, is predicted to affect the extent of damage they cause their hosts (virulence). High relatedness is generally assumed to favour less competitive interactions, but the relationship between relatedness and virulence is crucially dependent on the social behaviour in question. Here, we discuss the rather limited body of experimental work that addresses how kin-selected social behaviours affect virulence. First, if prudent use of host resources (a form of cooperation) maximizes the transmission success of the parasite population, decreased relatedness is predicted to result in increased host exploitation and virulence. Experimental support for this well-established theoretical result is surprisingly limited. Second, if parasite within-host growth rate is a positive function of cooperation (that is, when individuals need to donate public goods, such as extracellular enzymes), virulence is predicted to increase with increasing relatedness. The limited studies testing this hypothesis are broadly consistent with this prediction. Finally, there is some empirical evidence supporting theory that suggests that spiteful behaviours are maximized at intermediate degrees of relatedness, which, in turn, leads to minimal virulence because of the reduced growth rate of the infecting population. We highlight the need for further thorough experimentation on the role of kin selection in the evolution of virulence and identify additional biological complexities to these simple frameworks.     

Lineage, Sex, and Wealth as Moderators of Kin Investment

Supporting Hamilton’s inclusive fitness theory, archival analyses of inheritance patterns in wills have revealed that people invest more of their estates in kin of closer genetic relatedness. Recent classroom experiments have shown that this genetic relatedness effect is stronger for relatives of direct lineage (children, grandchildren) than for relatives of collateral lineage (siblings, nieces, nephews). In the present research, multilevel modeling of more than 1,000 British Columbian wills revealed a positive effect of genetic relatedness on proportions of estates allocated to relatives. This effect was qualified by an interaction with lineage, such that it was stronger for direct than for collateral relatives. Exploratory analyses of the moderating role of benefactors’ sex and estate values showed the genetic relatedness effect was stronger among female and wealthier benefactors. The importance of these moderators to understanding kin investment in modern humans is discussed.     

Biases in Visual,Auditory, and Audiovisual Perception of Space

Localization of objects and events in the environment is critical for survival, as many perceptual and motor tasks rely on estimation of spatial location. Therefore, it seems reasonable to assume that spatial localizations should generally be accurate. Curiously, some previous studies have reported biases in visual and auditory localizations, but these studies have used small sample sizes and the results have been mixed. Therefore, it is not clear (1) if the reported biases in localization responses are real (or due to outliers, sampling bias, or other factors), and (2) whether these putative biases reflect a bias in sensory representations of space or a priori expectations (which may be due to the experimental setup, instructions, or distribution of stimuli). Here, to address these questions, a dataset of unprecedented size (obtained from 384 observers) was analyzed to examine presence, direction, and magnitude of sensory biases, and quantitative computational modeling was used to probe the underlying mechanism(s) driving these effects. Data revealed that, on average, observers were biased towards the center when localizing visual stimuli, and biased towards the periphery when localizing auditory stimuli. Moreover, quantitative analysis using a Bayesian Causal Inference framework suggests that while pre-existing spatial biases for central locations exert some influence, biases in the sensory representations of both visual and auditory space are necessary to fully explain the behavioral data. How are these opposing visual and auditory biases reconciled in conditions in which both auditory and visual stimuli are produced by a single event? Potentially, the bias in one modality could dominate, or the biases could interact/cancel out. The data revealed that when integration occurred in these conditions, the visual bias dominated, but the magnitude of this bias was reduced compared to unisensory conditions. Therefore, multisensory integration not only improves the precision of perceptual estimates, but also the accuracy.     

Aunts and Mothers: Adaptive Implications of Allomaternal Behavior of Nonhuman Primates

Explanations of the function of behavior directed toward young primates by conspecifc females other than the mother have emphasized variow outcomes beneficial to aunts, I' mothers, infants, or some combination thereof. There is little evidence, however, that allomothering benefits mothers or infants to any signifcant degree; allomothering is selfish behavior with highly variable consequences roughly predzctable on the basis of genealogical ties between participants. Selective consequences of infant kidnapping and aunting-to-death are examined, and a hypothesis is suggested concerning the adaptive significance for mothering of allomothering. [adoption, infant-stealing, behavioral selection]     

Kin structure and shoal composition dynamics in the guppy, Poecilia reticulata

Although kin associations between fish can develop in the laboratory, the importance of kin structure in natural social groups remains uncertain. Guppies ( Poecilia reticulata ) possess many behavioural and life-history traits that promote kin structure, and so constitute ideal candidates for testing its general significance amongst fish. We collected 25 adult only shoals from ∼150 m stretches along two Trinidadian rivers. The 272 sampled fish were genotyped from a pool of seven hypervariable microsatellite loci. Although mark-recapture experiments have previously detected male-biased dispersal, which is predicted from the guppy mating system and which may have important implications for population differentiation, we found no sex-biases in dispersal between shoals. Because sex-biased dispersal was not evident, males and females were pooled in analyses of kin structure. Relatedness levels within each shoal did not differ significantly from zero, indicating that kin selection does not contribute to gross structure. Instead, our data is more consistent with the hypothesis that individual-level selection underlies shoal composition dynamics. These dynamics have important implications for the evolution of cooperative behaviour in guppies.     

Kin competition,natal dispersal and the moulding of senescence by natural selection

Most theoretical models for the evolution of senescence have assumed a very large, well mixed population. Here, we investigate how limited dispersal and kin competition might influence the evolution of ageing by deriving indicators of the force of selection, similar to Hamilton (Hamilton 1966 J. Theor. Biol. 12, 12–45). Our analytical model describes how the strength of selection on survival and fecundity changes with age in a patchy population, where adults are territorial and a fraction of juveniles disperse between territories. Both parent–offspring competition and sib competition then affect selection on age-specific life-history traits. Kin competition reduces the strength of selection on survival. Mutations increasing mortality in some age classes can even be favoured by selection, but only when fecundity deteriorates rapidly with age. Population structure arising from limited dispersal however selects for a broader distribution of reproduction over the lifetime, potentially slowing down reproductive senescence. The antagonistic effects of limited dispersal on age schedules of fecundity and mortality cast doubts on the generality of conditions allowing the evolution of ‘suicide genes’ that increase mortality rates without other direct pleiotropic effects. More generally, our model illustrates how limited dispersal and social interactions can indirectly produce patterns of antagonistic pleiotropy affecting vital rates at different ages.     

Kin selection, quorum sensing and virulence in pathogenic bacteria

Bacterial growth and virulence often depends upon the cooperative release of extracellular factors excreted in response to quorum sensing (QS). We carried out an in vivo selection experiment in mice to examine how QS evolves in response to variation in relatedness (strain diversity), and the consequences for virulence. We started our experiment with two bacterial strains: a wild-type that both produces and responds to QS signal molecules, and a lasR (signal-blind) mutant that does not release extracellular factors in response to signal. We found that: (i) QS leads to greater growth within hosts; (ii) high relatedness favours the QS wild-type; and (iii) low relatedness favours the lasR mutant. Relatedness matters in our experiment because, at relatively low relatedness, the lasR mutant is able to exploit the extracellular factors produced by the cells that respond to QS, and hence increase in frequency. Furthermore, our results suggest that because a higher relatedness favours cooperative QS, and hence leads to higher growth, this will also lead to a higher virulence, giving a relationship between relatedness and virulence that is in the opposite direction to that usually predicted by virulence theory.     

Quantifying Spike Train Oscillations: Biases,Distortions and Solutions

Estimation of the power spectrum is a common method for identifying oscillatory changes in neuronal activity. However, the stochastic nature of neuronal activity leads to severe biases in the estimation of these oscillations in single unit spike trains. Different biological and experimental factors cause the spike train to differentially reflect its underlying oscillatory rate function. We analyzed the effect of factors, such as the mean firing rate and the recording duration, on the detectability of oscillations and their significance, and tested these theoretical results on experimental data recorded in Parkinsonian non-human primates. The effect of these factors is dramatic, such that in some conditions, the detection of existing oscillations is impossible. Moreover, these biases impede the comparison of oscillations across brain regions, neuronal types, behavioral states and separate recordings with different underlying parameters, and lead inevitably to a gross misinterpretation of experimental results. We introduce a novel objective measure, the "modulation index", which overcomes these biases, and enables reliable detection of oscillations from spike trains and a direct estimation of the oscillation magnitude. The modulation index detects a high percentage of oscillations over a wide range of parameters, compared to classical spectral analysis methods, and enables an unbiased comparison between spike trains recorded from different neurons and using different experimental protocols.     

Kin selection,social grooming and the removal of ectoparasites: A theoretical investigation

This paper considers how individuals should apportion their altruism among their relatives, with particular reference to social grooming in primates. It is concluded that there are no good reasons to expect an altruist to deploy its altruism among other individuals in proportion to its coefficients of relatedness to them. Various factors may cause an individual to be altruistic not just to its closest relative. One factor which is probably of widespread importance is when altruism reaches a point of diminishing returns, so that an increase in aid given is not accompanied by a proportional increase in benefit received. Quantitative predictions are made for social grooming with special reference to its possible function of ectoparasite removal.     

Estimating the Biases Associated with Self-Perceived,Self-Reported,and Measured BMI on Mental Health

Purpose

The purpose of the study is to explore the relationship between individuals'' perceptions of their weight-status, self-reported height and weight, and measured weight status.

Methods

A national survey of 9,248 adolescents (47% male) between the ages of 11 and 27 is analyzed to determine whether inaccuracies in reporting are caused by misperception or conscious intent, and whether there tends to be a systematic bias in how individuals self-report. Self-esteem was used as an example of an important outcome variable in order to illustrate the magnitudes of the biases that may arise when using different measures of body size.

Results

Our results indicate that measured obesity status is associated with the reduction in Rosenberg Self-Esteem (RSE) of 0.30 points (p-value 0.005) among adolescents and 0.20 points (p-value 0.002) among young adults; in addition, using self-reported height and weight as opposed to measured height and weight does not result in a statistically detectable difference in the estimates.

Conclusions

Individuals'' self-reports of height and weight are not as unreliable as we might have expected. Although estimates from measured height and weight are preferred, in the absence of such measures, self-reported measures would likely be a reliable alternative. The differences in self-perception of weight status, however, imply that it is not comparable to measured weight categories.     

Kin selection-mutation balance: a model for the origin, maintenance, and consequences of social cheating

Social conflict, in the form of intraspecific selfish "cheating," has been observed in a number of natural systems. However, a formal, evolutionary genetic theory of social cheating that provides an explanatory, predictive framework for these observations is lacking. Here we derive the kin selection-mutation balance, which provides an evolutionary null hypothesis for the statics and dynamics of cheating. When social interactions have linear fitness effects and Hamilton's rule is satisfied, selection is never strong enough to eliminate recurrent cheater mutants from a population, but cheater lineages are transient and do not invade. Instead, cheating lineages are eliminated by kin selection but are constantly reintroduced by mutation, maintaining a stable equilibrium frequency of cheaters. The presence of cheaters at equilibrium creates a "cheater load" that selects for mechanisms of cheater control, such as policing. We find that increasing relatedness reduces the cheater load more efficiently than does policing the costs and benefits of cooperation. Our results provide new insight into the effects of genetic systems, mating systems, ecology, and patterns of sex-limited expression on social evolution. We offer an explanation for the widespread cheater/altruist polymorphism found in nature and suggest that the common fear of conflict-induced social collapse is unwarranted.     

Biases in the assays of steroids and their binding proteins

Many immunoassays exhibit a bias. In such assays, the results are inaccurate, i.e. they deviate from the true value. The biases are mostly due to interfering compounds originating from the biological material assayed and/or from reagents. Sometimes systematic errors in calculation are also involved. The magnitude of the bias should be determined for every assay method, in order to make possible an assessment of reliability of the method. Biases frequently occur also in the measurements of steroid binding proteins, such as receptors, sex hormone binding globulin, corticosteroid binding globulin, etc. These biases are mostly due to the assumption that the measurements are performed under saturation conditions. These biases can be avoided by conducting the measurements at several concentrations of the ligand and by an appropriate correction for non-specific (low affinity) binding. In the assays of "free" steroids, biases are frequently encountered because of the disturbance of equilibrium in the course of the measurement proper. These biases can be minimized by a careful choice of experimental conditions.