Rational choice,neuroeconomy and mixed emotions

Experimental psychology has shown differences between predictions of theory of decision and human choices. Emotions like regret can partly explain these differences. Neuroimagery used in combination with behavioural economics (neuroeconomics) has been used in order to try to disentangle the different emotional and rational factors (regret, rejoicing, reward, costs, uncertainty, trade-off between positive and negative aspects of different options). Emotions then appear as much more complex and mixed affective states than usually assumed. Not only might we feel a positive affect in punishing unfair partners, but mixed emotions can, for example, combine transmutation of previous anxiety into relief and elation by comparison with another less exciting option (elating relief). At the level of complexity of these mixed emotions—which we formally represent by comparisons between ‘unexpected utilities’ and expected ones—the main biases that Kahnemann and Tversky have shown can be explained. In spite of the complexity of these mixed emotions, some of these hypotheses might be partially tested by brain imagery.     

An availability-acceptability theory of suicide

A theory was proposed to account for the appearance of suicide. The lack of immediate availability of the preferred means for killing oneself and the religious belief that suicide is an unacceptable action both serve to reduce the likelihood of suicide. This theory was tested and confirmed using an ecological analysis of the continental states of the USA. The two variables together accounted for 46 percent of the variation of the suicide rates of the states.     

Computational mate choice: theory and empirical evidence

The present review is based on the thesis that mate choice results from information-processing mechanisms governed by computational rules and that, to understand how females choose their mates, we should identify which are the sources of information and how they are used to make decisions. We describe mate choice as a three-step computational process and for each step we present theories and review empirical evidence. The first step is a perceptual process. It describes the acquisition of evidence, that is, how females use multiple cues and signals to assign an attractiveness value to prospective mates (the preference function hypothesis). The second step is a decisional process. It describes the construction of the decision variable (DV), which integrates evidence (private information by direct assessment), priors (public information), and value (perceived utility) of prospective mates into a quantity that is used by a decision rule (DR) to produce a choice. We make the assumption that females are optimal Bayesian decision makers and we derive a formal model of DV that can explain the effects of preference functions, mate copying, social context, and females' state and condition on the patterns of mate choice. The third step of mating decision is a deliberative process that depends on the DRs. We identify two main categories of DRs (absolute and comparative rules), and review the normative models of mate sampling tactics associated to them. We highlight the limits of the normative approach and present a class of computational models (sequential-sampling models) that are based on the assumption that DVs accumulate noisy evidence over time until a decision threshold is reached. These models force us to rethink the dichotomy between comparative and absolute decision rules, between discrimination and recognition, and even between rational and irrational choice. Since they have a robust biological basis, we think they may represent a useful theoretical tool for behavioural ecologist interested in integrating proximate and ultimate causes of mate choice.     

The biosocial female choice theory of social stratification

For decades, the study of social stratification has been dominated by environmental theories. Herein a theory is proposed that contains both biological and sociocultural elements. The theory asserts that most human females, like females of many other mammalian species, have evolved mating preferences biased toward males who are competent in provisioning resources. This female bias is hypothesized to have been naturally selected because females with these biases nearly always have had a reproductive edge over females who lack such a bias. One result of this bias is that human females preferentially mate with males who strive to rise in social status. This, in turn, has favored males who attain or at least strive for high social status, and who advertise and even exaggerate whatever status they already have achieved. At the genetic level, the theory postulates that alleles have accumulated on the human genome that promote social status-striving and achievement to varying degrees. To account for why males are more prone toward status-striving than females, the theory contends that one or more genes on the Y-chromosome interact with genes on the remaining human chromosomes to incline males to gravitate toward social hierarchies and to strive for niches that are relatively high in those hierarchies. Both tested and untested hypotheses are derived from the theory and compared to the empirical evidence currently available.     

Retirement investment theory explains patterns in songbird nest-site choice

When opposing evolutionary selection pressures act on a behavioural trait, the result is often stabilizing selection for an intermediate optimal phenotype, with deviations from the predicted optimum attributed to tracking a moving target, development of behavioural syndromes or shifts in riskiness over an individual''s lifetime. We investigated nest-site choice by female golden-winged warblers, and the selection pressures acting on that choice by two fitness components, nest success and fledgling survival. We observed strong and consistent opposing selection pressures on nest-site choice for maximizing these two fitness components, and an abrupt, within-season switch in the fitness component birds prioritize via nest-site choice, dependent on the time remaining for additional nesting attempts. We found that females consistently deviated from the predicted optimal behaviour when choosing nest sites because they can make multiple attempts at one fitness component, nest success, but only one attempt at the subsequent component, fledgling survival. Our results demonstrate a unique natural strategy for balancing opposing selection pressures to maximize total fitness. This time-dependent switch from high to low risk tolerance in nest-site choice maximizes songbird fitness in the same way a well-timed switch in human investor risk tolerance can maximize one''s nest egg at retirement. Our results also provide strong evidence for the adaptive nature of songbird nest-site choice, which we suggest has been elusive primarily due to a lack of consideration for fledgling survival.     

How evolutionary biology challenges the classical theory of rational choice

A fundamental philosophical question that arises in connection with evolutionary theory is whether the fittest patterns of behavior are always the most rational. Are fitness and rationality fully compatible? When behavioral rationality is characterized formally as in classical decision theory, the question becomes mathematically meaningful and can be explored systematically by investigating whether the optimally fit behavior predicted by evolutionary process models is decision-theoretically coherent. Upon investigation, it appears that in nontrivial evolutionary models the expected behavior is not always in accord with the norms of the standard theory of decision as ordinarily applied. Many classically irrational acts, e.g. betting on the occurrence of one event in the knowledge that the probabilities favor another, can under certain circumstances constitute adaptive behavior. One interesting interpretation of this clash is that the criterion of rationality offered by classical decision theory is simply incorrect (or at least incomplete) as it stands, and that evolutionary theory should be called upon to provide a more generally applicable theory of rationality. Such a program, should it prove feasible, would amount to the logical reduction of the theory of rational choice to evolutionary theory.     

Rational approaches to control of iron deficiency other than plant breeding and choice of resistant cultivars

Satisfactory progress has been made in recent years in preventing and correcting Fe deficiency in plants, and more can be expected in the future. Important advances include uses of acid- and Fe-fortified organic wastes and use of amended sulfur-pyrite mixes in soil. Three different approaches with organics are as an acidified matrix with Fe, as a means of chelating Fe, and as a carrier of acidifiers. Several procedures can help minimize Fe deficiency. (1) Avoid mis-management of soil physical properties and overirrigation. (2) Avoid nutrient imbalance, such as excess P or excess micronutrients. (3) Use preplant application of mildly acid-organic matter-Fe-sulfur or pyrite mixes worked into zones of soil or banded into seed rows. It is important that small bands or spots in soil be completely neutralized of CaCO₃. (4) Where foliar sprays can or need be used, especially to correct mild chlorosis, use ferrous compounds prepared to be delivered at pH 3± so that the Fe does not easily oxidize or precipitate in the solution. (5) For established trees that have become Fe deficient, inject, via slant drilling of small holes in tree trunks, dilute ferric ammonium citrate sufficient to supply not more than 100 mg kg^-1 Fe to leaves (dry weight basis). Most but not all species will respond. Procedure may be repeated in two or three weeks if necessary. (6) Iron chelates may be used in drip irrigation. If soil is sandy, soil pH not over 7.2, FeDTPA may be used; otherwise, FeEDDHA should be used. If the Fe is supplied with no other nutrients, pH may be at 4 and some FeSO₄ included to recycle the chelating agents. If Fe is used without chelating agents, the pH may be 1.0 or less and other nutrients included. (7) Urea-acid sulfate-Fe sulfate may be irrigated into soil around plants, especially if soil was polymer treated. (8) Efficiency of use of Fe chelates may be increased by making them slow release or by applying with seeds.     

Individuals,groups, fitness and utility: multi-level selection meets social choice theory

In models of multi-level selection, the property of Darwinian fitness is attributed to entities at more than one level of the biological hierarchy, e.g. individuals and groups. However, the relation between individual and group fitness is a controversial matter. Theorists disagree about whether group fitness should always, or ever, be defined as total (or average) individual fitness. This paper tries to shed light on the issue by drawing on work in social choice theory, and pursuing an analogy between fitness and utility. Social choice theorists have long been interested in the relation between individual and social utility, and have identified conditions under which social utility equals total (or average) individual utility. These ideas are used to shed light on the biological problem.     

The model of the reward choice basing on the theory of reinforcement learning

We developed the model of alimentary instrumental conditioned bar-pressing reflex for cats making a choice between either immediate small reinforcement ("impulsive behavior") or delayed more valuable reinforcement ("self-control behavior"). Our model is based on the reinforcement learning theory. We emulated dopamine contribution by discount coefficient of this theory (a subjective decrease in the value of a delayed reinforcement). The results of computer simulation showed that "cats" with large discount coefficient demonstrated "self-control behavior"; small discount coefficient was associated with "impulsive behavior". This data are in agreement with the experimental data indicating that the impulsive behavior is due to a decreased amount of dopamine in striatum.     

The heterozygosity theory of extra-pair mate choice in birds: a test and a cautionary note

Although extra-pair fertilizations (EPF) are common in socially monogamous systems, the benefits to females remain elusive. One potential benefit that recently has begun to receive empirical attention is increased offspring heterozygosity. We tested the heterozygosity hypothesis in the black-throated blue warbler Dendroica caerulescens using a panel of five microsatellite loci. We did not find any evidence that male heterozygosity influenced female extra-pair mating patterns, that females choose genetically dissimilar extra-pair mates, nor that extra-pair offspring were more heterozygous than within-pair offspring. However, simple Monte Carlo simulations indicated that the number of microsatellite loci used in this study, and most other recent studies, would detect an effect of heterozygosity only if that effect is pronounced. Thus, we were unable to demonstrate any effect of offspring heterozygosity in our study species, but a more subtle effect remains possible. Researchers wishing to test this hypothesis should use a large number of genetic markers and interpret negative results cautiously.     

Adult ADHD and suicide

While suicidal behaviour has been implicated in a plethora of psychiatric disorders including depression, psychoses and substance abuse, its association with adult ADHD is largely under-researched. Given that emotional instability and the high prevalence of comorbid conditions such as mood disorders and alcohol/drug dependence are typical for ADHD, the question of suicide risk must not be neglected in this patient group. A review of the current literature focusing on this issue provides strong evidence that ADHD patients are at a significant risk for experiencing suicidal ideations and committing suicide. For daily clinical practice, it is therefore essential to incorporate this aspect into the diagnostic and therapeutic process and to take preventive measures.     

Rational design for multifunctional non-liposomal lipid-based nanocarriers for cancer management: theory to practice

Nanomedicines have gained more and more attention in cancer therapy thanks to their ability to enhance the tumour accumulation and the intracellular uptake of drugs while reducing their inactivation and toxicity. In parallel, nanocarriers have been successfully employed as diagnostic tools increasing imaging resolution holding great promises both in preclinical research and in clinical settings. Lipid-based nanocarriers are a class of biocompatible and biodegradable vehicles that provide advanced delivery of therapeutic and imaging agents, improving pharmacokinetic profile and safety. One of most promising engineering challenges is the design of innovative and versatile multifunctional targeted nanotechnologies for cancer treatment and diagnosis. This review aims to highlight rational approaches to design multifunctional non liposomal lipid-based nanocarriers providing an update of literature in this field.