On the possibility of identifying human subjects using behavioural complexity analyses

Background: Identification of human subjects using a geometric approach to complexity analysis of behavioural data is designed to provide a basis for a more precise diagnosis leading towards personalised medicine. Methods: The approach is based on capturing behavioural time-series that can be characterized by a fractional dimension using non-invasive longer-time acquisitions of heart rate, perfusion, blood oxygenation, skin temperature, relative movement and steps frequency. The geometry based approach consists in the analysis of the area and centroid of convex hulls encapsulating the behavioural data represented in Euclidian index spaces based on the scaling properties of the self-similar normally distributed behavioural time-series of the above mentioned quantities. Results: An example demonstrating the presented approach of behavioural fingerprinting is provided using sensory data of eight healthy human subjects based on approximately fifteen hours of data acquisition. Our results show that healthy subjects can be factorized to different similarity groups based on a particular choice of a convex hull in the corresponding Euclidian space. One of the results indicates that healthy subjects share only a small part of the convex hull pertaining to a highly trained individual from the geometric comparison point of view. Similarly, the presented pair-wise individual geometric similarity measure indicates large differences among the subjects suggesting the possibility of neuro-fingerprinting. Conclusions: Recently introduced multi-channel body-attached sensors provide a possibility to acquire behavioural time-series that can be mathematically analysed to obtain various objective measures of behavioural patterns yielding behavioural diagnoses favouring personalised treatments of, e.g., neuropathologies or aging.     

Behavioural syndromes and social insects: personality at multiple levels

Animal personalities or behavioural syndromes are consistent and/or correlated behaviours across two or more situations within a population. Social insect biologists have measured consistent individual variation in behaviour within and across colonies for decades. The goal of this review is to illustrate the ways in which both the study of social insects and of behavioural syndromes has overlapped, and to highlight ways in which both fields can move forward through the synergy of knowledge from each. Here we, (i) review work to date on behavioural syndromes (though not always referred to as such) in social insects, and discuss mechanisms and fitness effects of maintaining individual behavioural variation within and between colonies; (ii) summarise approaches and principles from studies of behavioural syndromes, such as trade‐offs, feedback, and statistical methods developed specifically to study behavioural consistencies and correlations, and discuss how they might be applied specifically to the study of social insects; (iii) discuss how the study of social insects can enhance our understanding of behavioural syndromes—research in behavioural syndromes is beginning to explore the role of sociality in maintaining or developing behavioural types, and work on social insects can provide new insights in this area; and (iv) suggest future directions for study, with an emphasis on examining behavioural types at multiple levels of organisation (genes, individuals, colonies, or groups of individuals).     

Personality-dependent dispersal in the invasive mosquitofish: group composition matters

Understanding/predicting ecological invasions is an important challenge in modern ecology because of their immense economical and ecological costs. Recent studies have revealed that within-species variation in behaviour (i.e. animal personality) can shed light on the invasion process. The general hypothesis is that individuals' personality type may affect their colonization success, suggesting that some individuals might be better invaders than others. We have recently shown that, in the invasive mosquitofish (Gambusia affinis), social personality trait was an important indicator of dispersal distance, with more asocial individuals dispersing further. Here, we tested how mean personality within a population, in addition to individual personality type, affect dispersal and settlement decisions in the mosquitofish. We found that individual dispersal tendencies were influenced by the population's mean boldness and sociability score. For example, individuals from populations with more asocial individuals or with more bold individuals are more likely to disperse regardless of their own personality type. We suggest that identifying behavioural traits facilitating invasions, even at the group level, can thus have direct applications in pest management.     

Aggressive females become aggressive males in a sex-changing reef fish

Many animal populations display consistent individual differences in suites of correlated behaviours. While these so called 'animal personalities' can substantially influence the ecology and evolution of populations, little is known about cross-sex correlations of behaviour and thus the potential of personality to limit sex-specific behavioural adaptations. Here, we experimentally induced sex-change in the sequentially hermaphroditic reef fish Parapercis cylindrica and demonstrate the existence of tight cross-sex correlations for two behaviours with presumed different sex-specific optima. Individuals that were relatively more active and aggressive females were found to become relatively more active and aggressive males. By identifying personality as a potential genetic constraint on the resolution of intralocus sexual conflict over behaviour, our findings have important ecological and evolutionary implications for a wide range of species.     

Reproductive success in a socially polymorphic spider: social individuals experience depressed reproductive success in isolation

1. Correlated individual differences in behaviour across ecological contexts, or behavioural syndromes, can theoretically constrain individuals' ability to optimally adjust their behaviour for specific contexts. 2. Female Anelosimus studiosus exhibit a unique behavioural polymorphism: ‘social’ females are tolerant of conspecifics and aggregate in multi‐female colonies, while ‘solitary’ females aggressively defend their singleton webs from intrusion by adult female conspecifics. Previous work found that social females are also less aggressive toward prey and are more fearful of predators. 3. In this study we quantify potential fitness consequences of these correlated behaviours by examining the potential and realised fecundities of the two phenotypes in naturally occurring colonies, and by quantifying their ability to rear offspring as singleton individuals. 4. There were no differences in the fecundities of laboratory‐reared females between the phenotypes, nor were there differences in field‐collected brooding females from naturally occurring solitary and social nests. 5. Brooding females from solitary and social colonies that were isolated in new nests for the growing season were both capable of rearing their broods; however, females from solitary nests had significantly greater success. 6. These results suggest a fitness consequence to the reduced‐aggression syndrome of social females that may represent a general impediment to the evolution of sociality in spiders.     

The return of the whole organism

The long trend towards analysis at lower and lower levels is starting to reverse. The new integrative studies must make use of the resources uncovered by molecular biology but should also use the characteristics of whole organisms to measure the outcomes of developmental processes. Two examples are given of how movement between levels of analysis is being used with increasing power and promise. The first is the study of behavioural imprinting in birds where many of the molecular and neural mechanisms involved have been uncovered and are now being integrated to explain the behaviour of the whole animal. The second is the triggering during sensitive periods in early life by environmental events of one of several alternative modes of development leading to different phenotypes. A renewed focus on the whole organism is also starting to change the face of evolutionary biology. The decision-making and adaptability of the organism is recognized an important driver of evolution and is increasingly seen as an alternative to the gene-focused views.     

Psychoactive pollution suppresses individual differences in fish behaviour

Environmental contamination by pharmaceuticals is global, substantially altering crucial behaviours in animals and impacting on their reproduction and survival. A key question is whether the consequences of these pollutants extend beyond mean behavioural changes, restraining differences in behaviour between individuals. In a controlled, two-year, multigenerational experiment with independent mesocosm populations, we exposed guppies (Poecilia reticulata) to environmentally realistic levels of the ubiquitous pollutant fluoxetine (Prozac). Fish (unexposed: n = 59, low fluoxetine: n = 57, high fluoxetine: n = 58) were repeatedly assayed on four separate occasions for activity and risk-taking behaviour. Fluoxetine homogenized individuals'' activity, with individual variation in populations exposed to even low concentrations falling to less than half that in unexposed populations. To understand the proximate mechanism underlying these changes, we tested the relative contribution of variation within and between individuals to the overall decline in individual variation. We found strong evidence that fluoxetine erodes variation in activity between but not within individuals, revealing the hidden consequences of a ubiquitous contaminant on phenotypic variation in fish—likely to impair adaptive potential to environmental change.     

Plasticity in activity and latency to explore differs between juvenile Atlantic cod Gadus morhua across a temperature gradient

In the current study activity and latency to explore, as well as the correlation of these traits, were examined in individually marked juvenile Gadus morhua at 7, 10 and 13° C. It was concluded that individual rank order of both traits was maintained across temperature but that the level of change differed between individuals.     

Blood Parasite Infection Intensity Covaries with Risk‐Taking Personality in Male Carpetan Rock Lizards (Iberolacerta cyreni)

Identifying evolutionary and developmental mechanisms underlying consistent between‐individual differences in behaviour is the main goal in ‘animal personality studies’. Here, we explored whether activity and risk‐taking varied consistently between individuals and correlated to various – potentially fitness linked – male traits in Carpetan rock lizards (Iberolacerta cyreni). Lizards showed significant consistency within both behaviours, implying the presence of activity and risk‐taking personalities. However, there were no correlation between activity and risk‐taking, neither on the between‐ nor on the within‐individual levels, implying the absence of a behavioural syndrome. We found a strong link between the intensity of blood parasite (Haemogregarinidae) infection and risk‐taking: lizards with higher infection intensity took more risk. While we cannot distinguish cause from causative in the parasite intensity – risk‐taking correlation – our results are in line with the asset protection hypothesis predicting that individuals with lower future reproductive value should focus on the current reproductive event and take higher risk.     

Predation mediated population divergence in complex behaviour of nine‐spined stickleback (Pungitius pungitius)

The proximate and ultimate explanations for behavioural syndromes (correlated behaviours – a population trait) are poorly understood, and the evolution of behavioural types (configuration of behaviours – an individual trait) has been rarely studied. We investigated population divergence in behavioural syndromes and types using individually reared, completely predator‐ or conspecific‐naïve adult nine‐spined sticklebacks (Pungitius pungitius) from two marine and two predatory fish free, isolated pond populations. We found little evidence for the existence of behavioural syndromes, but population divergence in behavioural types was profound: individuals from ponds were quicker in feeding, bolder and more aggressive than individuals from marine environments. Our data reject the hypothesis that behavioural syndromes exist as a result of genetic correlations between behavioural traits, and support the contention that different behavioural types can be predominant in populations differing in predation pressure, most probably as a result of repeated independent evolution of separate behavioural traits.     

Innovation as part of a wider behavioural syndrome in the guppy: The effect of sex and body size

Recent work on animal personalities has shown that individuals within populations often differ consistently in various types of behaviour and that many of these behaviours correlate among individuals to form behavioural syndromes. Individuals of certain species have also been shown to differ in their rate of behavioural innovation in arriving at novel solutions to new and existing problems (e.g., mazes, novel foods). Here, we investigate whether behaviours traditionally studied in personality research are correlated with individual rates of innovation as part of a wider behavioural syndrome. Guppies (Poecilia reticulata) of both sexes from three different wild population sources were assessed: (a) exploration of an open area; (b) speed through a three‐dimensional maze; (c) investigation of a novel object; and (d) attraction to a novel food. The covariance structure (syndrome structure) was examined using structural equation modelling. The best model separated behaviours relating to activity in all contexts from rates of exploration/investigation and innovation. Innovative behaviour (utilizing new food and moving through a novel area) in these fish therefore forms part of the same syndrome as the traditional shy‐bold continuum (exploration of an open area and investigation of a novel object) found in many animal personality studies. There were no clear differences in innovation or syndrome structure between the sexes, or between the three different populations. However, body size was implicated as part of the behavioural syndrome structure, and because body size is highly correlated with age in guppies, this suggests that individual behavioural differences in personality/innovation in guppies may largely be driven by developmental state.     

Mutants affecting plasticity of phototactic behaviour in Drosophila melanogaster

Eight mutants of Drosophila m. have been isolated that fail to display longlasting modification of “choice tube phototaxis”. Two different classes of stocks defective in plasticity of phototaxis (dipp) can be discriminated: (1) Mutants which are affected in the stability of the Prolonged Depolarising Afterpotential (PDA) in the peripheral retinula cells R1–R6. (2) Mutants with normal PDA but abnormalities in fast escape phototaxis especially under conditions where only receptor cells R7–R8 serve as input for this behavioural trait.     

Why do men seek status? Fitness payoffs to dominance and prestige

In many human societies, high male social status associates with higher fertility, but the means by which status increases lifetime fitness have not been systematically investigated. We analyse the pathways by which male status begets reproductive success in a small-scale, Amerindian society. Men who are more likely to win a dyadic physical confrontation, i.e. dominant men, have higher intra-marital fertility for their age, and men with more community-wide influence, i.e. prestigious men, exhibit both higher intra-marital fertility and lower offspring mortality. Both forms of status elicit support from allies and deference from competitors, but high status men are not provisioned more than their peers. Prestigious but not dominant men marry wives who first give birth at earlier ages, which multivariate analysis suggests is the strongest pathway between status and fitness in this population. Furthermore, men are motivated to pursue status because of fitness gains both within and outside of marital unions: dominant and prestigious men have more in-pair surviving offspring as well as more extra-marital affairs.     

Evidence of social learning in black-and-white ruffed lemurs (Varecia variegata)

Although many studies have examined social learning capabilities in apes and monkeys, experiments involving prosimians remain largely absent. We investigated the potential for social learning in black-and-white ruffed lemurs using a two-action foraging task. Eight individuals were divided into two experimental groups and exposed to conspecifics using one of two techniques to access food. Subjects were then given access to the apparatus and their retrieval techniques were recorded and compared. All subjects made their first retrieval using the technique they observed being demonstrated, and there were significant differences between the two groups in their overall response patterns. These results suggest that prosimians are capable of social learning and that additional long-term field studies may reveal the presence of behavioural traditions similar to those found in other primates.     

Man and other introduced organisms

Man's tremendously increased migratory potention, coupled with his ability to transport any material, causes ecological revolutions on most islands of this world–Fernandina and most smaller islands of the Galapagos being fortunate exceptions to that rule. It is proposed to make distinctions between species colonizing the Galapagos We can distinguish between those immigrant species which do not profit from man as a transport medium (independent immigrants) and those who do depend on him (man-dependent immigrants). These immigrants, in turn, may or may not be able to settle and these settlers may either gain a footing with or without depending on man's direct or indirect influence on the habitat (non-settlers, primary resource-using settlers, and secondary resource-using settlers). Introduced species represent a terrible attack on the biotic uniqueness of the Galapagos ecosystems. However, it is proposed to make better use of the scientific value of these introductions. For example, a case of selective impact of an introduced on an indigenous species was investigated: lava lizards of the genus Tropidurus seem to be more wary of moving objects on islands where cats have been introduced by man than on islands free of cats.
Under the peculiar Galapagos conditions it may turn out that science's most difficult and important task is to investigate and interpret man's role in such places.     

From hominins to humans: how sapiens became behaviourally modern

This paper contributes to a debate in the palaeoarchaeological community about the major time-lag between the origin of anatomically modern humans and the appearance of typically human cultural behaviour. Why did humans take so long—at least 100 000 years—to become ‘behaviourally modern’? The transition is often explained as a change in the intrinsic cognitive competence of modern humans: often in terms of a new capacity for symbolic thought, or the final perfection of language. These cognitive breakthrough models are not satisfactory, for they fail to explain the uneven palaeoanthropological record of human competence. Many supposed signature capacities appear (and then disappear) before the supposed cognitive breakthrough; many of the signature capacities disappear again after the breakthrough. So, instead of seeing behavioural modernity as a simple reflection of a new kind of mind, this paper presents a niche construction conceptual model of behavioural modernity. Humans became behaviourally modern when they could reliably transmit accumulated informational capital to the next generation, and transmit it with sufficient precision for innovations to be preserved and accumulated. In turn, the reliable accumulation of culture depends on the construction of learning environments, not just intrinsic cognitive machinery. I argue that the model is (i) evolutionarily plausible: the elements of the model can be assembled incrementally, without implausible selective scenarios; (ii) the model coheres with the broad palaeoarchaeological record; (iii) the model is anthropologically and ethnographically plausible; and (iv) the model is testable, though only in coarse, preliminary ways.