A comparative review of motivational systems using classical control theory

Expressing Personality Through Non-verbal Behaviour in Real-Time Interaction

The attribution of traits plays an important role as a heuristic for how we interact with others. Many psychological models of personality are analytical in that they derive a classification from reported or hypothesised behaviour. In the work presented here, we follow the opposite approach: Our personality model generates behaviour that leads an observer to attribute personality characteristics to the actor. Concretely, the model controls all relevant aspects of non-verbal behaviour such as gaze, facial expression, gesture, and posture. The model, embodied in a virtual human, affords to realistically interact with participants in real-time. Conceptually, our model focuses on the two dimensions of extra/introversion and stability/neuroticism. In the model, personality parameters influence both, the internal affective state as well as the characteristic of the behaviour execution. Importantly, the parameters of the model are based on empirical findings in the behavioural sciences. To evaluate our model, we conducted two types of studies. Firstly, passive experiments where participants rated videos showing variants of behaviour driven by different personality parameter configurations. Secondly, presential experiments where participants interacted with the virtual human, playing rounds of the Rock-Paper-Scissors game. Our results show that the model is effective in conveying the impression of the personality of a virtual character to users. Embodying the model in an artificial social agent capable of real-time interactive behaviour is the only way to move from an analytical to a generative approach to understanding personality, and we believe that this methodology raises a host of novel research questions in the field of personality theory.

Novelty of the arena impairs the cortisol-related increase in the aggression of matrinxã (Brycon amazonicus)

The dichotomic effect of a cortisol level rise in vertebrate behavior has been widely observed. Generally, a chronic increase of the hormone level inhibits aggression, while an acute rise increases aggression. However, in this study, we show that this increase in aggression through an acute rise of cortisol also depends on the context in which the agonistic interaction occurs in the tropical fish matrinxã, Brycon amazonicus. We combined two factors: the type of housing (resident or non-resident in the trial arena) and the level of cortisol at the beginning of the fight (normal level - control, or high level - hydrocortisone-treated fish). The cortisol treatment increased the aggressiveness in the resident fish, but this effect was not observed in the non-resident fish, which fought in an unknown arena. The novelty of the arena may have elicited an "alerted state" in the non-resident fish; in this situation the fight was not the priority, and the cortisol effect in aggression could be impaired by a conflict between motivational systems (fear and aggression). In our knowledge, in fish, the increase of aggression promoted by an acute rise in cortisol levels was always tested and observed in a resident context, and the inhibition of cortisol effect in the agonist behavior is demonstrated for the first time. As the cortisol effect in aggression is observed in several taxa, the inhibition of aggressiveness increased by the novelty of the arena should be investigated in other groups to clarify the dynamics of this effect of cortisol in animal behavior.

Brain mechanisms for offense, defense, and submission

A preliminary attempt is made to analyze the intraspecific aggressive behavior of mammals in terms of specific neural circuitry. The results of stimulation, lesion, and recording studies of aggressive behavior in cats and rats are reviewed and analyzed in terms of three hypothetical motivational systems: offense, defense, and submission. A critical distinction, derived from ethological theory, is made between motivating stimuli that simultaneously activate functional groupings of motor patterning mechanisms, and releasing and directing stimuli that are necessary for the activation of discrete motor patterning mechanisms. It is suggested that motivating stimuli activate pathways that converge upon sets of homogeneous neurons, called motivational mechanisms, whose activity determines the motivational state of the animal.

A defense motivational mechanism is hypothesized to be located in the midbrain central gray. In addition to tactile, auditory, and visual inputs from the paleospinothalamic tract, lateral lemniscus, and (perhaps) from the pretectum, it may receive inputs from a major forebrain pathway whose functional significance is not yet understood.

A submission motivational mechanism is also thought to be located in the central gray. In addition to inputs for defense, it is thought to receive a necessary input from a “consociate (social familiarity cue) modulator” located in the ventromedial hypothalamus, which can switch behavior from defense to submission. The location of the hypothetical offense motivational mechanism is not known, although the pathways by which it is activated are traced in some detail.

Brain mechanisms of aggression in primitive mammals and in primates are apparently similar to those in rats and cats.

From an animal's point of view: Motivation, fitness, and animal welfare

To study animal welfare empirically we need an objective basis for deciding when an animal is suffering. Suffering includes a wide range ofunpleasant emotional states such as fear, boredom, pain, and hunger. Suffering has evolved as a mechanism for avoiding sources ofdanger and threats to fitness. Captive animals often suffer in situations in which they are prevented from doing something that they are highly motivated to do. The “price” an animal is prepared to pay to attain or to escape a situation is an index ofhow the animal “feels” about that situation. Withholding conditions or commodities for which an animal shows “inelastic demand” (i.e., for which it continues to work despite increasing costs) is very likely to cause suffering. In designing environments for animals in zoos, farms, and laboratories, priority should be given to features for which animals show inelastic demand. The care ofanimals can thereby be based on an objective, animal-centered assessment of their needs.

The nature of human aggression

Human aggression is viewed from four explanatory perspectives, derived from the ethological tradition. The first consists of its adaptive value, which can be seen throughout the animal kingdom, involving resource competition and protection of the self and offspring, which has been viewed from a cost-benefit perspective. The second concerns the phylogenetic origin of aggression, which in humans involves brain mechanisms that are associated with anger and inhibition, the emotional expression of anger, and how aggressive actions are manifest. The third concerns the origin of aggression in development and its subsequent modification through experience. An evolutionary approach to development yields conclusions that are contrary to the influential social learning perspective, notably that physical aggression occurs early in life, and its subsequent development is characterized by learned inhibition. The fourth explanation concerns the motivational mechanisms controlling aggression: approached from an evolutionary background, these mechanisms range from the inflexible reflex-like responses to those incorporating rational decision-making.

Sex Differences in Aggression in Real-World Settings: A Meta-Analytic Review

Meta-analytic reviews of sex differences in aggression from real-world settings are described. They cover self-reports, observations, peer reports, and teacher reports of overall direct, physical, verbal, and indirect forms of aggression, as well as (for self-reports) trait anger. Findings are related to sexual selection theory and social role theory. Direct, especially physical, aggression was more common in males and females at all ages sampled, was consistent across cultures, and occurred from early childhood on, showing a peak between 20 and 30 years. Anger showed no sex differences. Higher female indirect aggression was limited to later childhood and adolescence and varied with method of measurement. The overall pattern indicated males’ greater use of costly methods of aggression rather than a threshold difference in anger.