Retrospective revaluation as simple associative learning

Backward blocking, unovershadowing and backward conditioned inhibition are examples of "retrospective revaluation" phenomena, that have been suggested to involve more than simple associative learning. Models of these phenomena have thus employed additional concepts, e.g. appealing to attentional effects or more elaborate learning mechanisms. I show that a suitable representation of stimuli, paired with a careful analysis of the discriminations faced by animals, leads to an account of these and other phenomena in terms of a simple "elemental" model of associative learning, with essentially the same learning mechanism as the Rescorla and Wagner (1972) model. I conclude with a discussion of some implications for theories of learning

Artificial neural networks as models of stimulus control

We evaluate the ability of artificial neural network models (multi-layer perceptrons) to predict stimulus-­response relationships. A variety of empirical results are considered, such as generalization, peak-shift (supernormality) and stimulus intensity effects. The networks were trained on the same tasks as the animals in the considered experiments. The subsequent generalization tests on the networks showed that the model replicates correctly the empirical results. It is concluded that these models are valuable tools in the study of animal behaviour

Modeling Society with Statistical Mechanics: an Application to Cultural Contact and Immigration

We introduce a general modeling framework to predict the outcomes, at the population level, of individual psychology and behavior. The framework prescribes that researchers build a cost function that embodies knowledge of what trait values (opinions, behaviors, etc.) are favored by individual interactions under given social conditions. Predictions at the population level are then drawn using methods from statistical mechanics, a branch of theoretical physics born to link the microscopic and macroscopic behavior of physical systems. We demonstrate our approach building a model of cultural contact between two cultures (e.g., immigration), showing that it is possible to make predictions about how contact changes the two cultures

The Geometry of Stimulus Control

Many studies, both in ethology and comparative psychology, have shown that animals react to modifications of familiar stimuli. This phenomenon is often referred to as generalisation. Most modifications lead to a decrease in responding, but to certain new stimuli an increase in responding is observed. This holds for both innate and learned behaviour. Here we propose a heuristic approach to stimulus control, or stimulus selection, with the aim of explaining these phenomena. The model has two key elements. First, we choose the receptor level as the fundamental stimulus space. Each stimulus is represented as the pattern of activation it induces in sense organs. Second, in this space we introduce a simple measure of `similarity' between stimuli by calculating how activation patterns overlap. The main advantage we recognise in this approach is that the generalisation of acquired responses emerges from a few simple principles which are grounded in the recognition of how animals actually perceive stimuli. Many traditional problems that face theories of stimulus control (e.g. the Spence-Hull theory of gradient interaction or ethological theories of stimulus summation) do not arise in the present framework. These problems include the amount of generalisation along different dimensions, peak-shift phenomena (with respect to both positive and negative shifts), intensity generalisation, and generalisation after conditioning on two positive stimuli

The evolution of brain lateralization: A game theoretical analysis of population structure

In recent years, it has become apparent that behavioural and brain lateralization is the rule rather than the exception among vertebrates. The study of lateralization has been so far the province of neurology and neuropsychology. We show how such research can be integrated with evolutionary biology to more fully understand lateralization. In particular, we address the fact that, within a species, left- and right-type individuals are often in a definite proportion different from 1/2 (e.g., hand use in humans). We argue that traditional explanations of brain lateralization (that it may avoid costly duplication of neural circuitry and reduce interference between functions) cannot account for this fact, because increased individual efficiency is unre- lated to the frequency of left- and right-type individuals in a population. A further puzzle is that, if a majority of individuals are of the same type, individual behaviour becomes more predictable to other organisms. Here we show that alignment of the direction of behavioural asymmetries in a population can arise as an evolutionarily stable strategy (ESS), when individually asymmetrical organisms must coordinate their behaviour with that of other asymmetrical organisms. Thus, brain and behavioural lateralization, as we know it in humans and other vertebrates, may have evolved under basically "social" selection pressures

Cultural evolution developing its own rules: The rise of conservatism and persuasion

In the human sciences, cultural evolution is often viewed as an autonomous process free of genetic influence. A question that follows is, If culture is not influenced by genes, can it take any path? Employing a simple mathematical model of cultural transmission in which individuals may copy each other's traits, we show that cultural evolution favors individuals who are weakly influenced by others and able to influence others. The model suggests that the cultural evolution of rules of cultural transmission tends to create populations that evolve rapidly toward conservatism, and that bias in cultural transmission may result purely from cultural dynamics. Freedom from genetic influence is not freedom to take any direction

Intensity generalisation: physiology and modelling of a neglected topic

I briefly review empirical data about the generalisation of acquired behaviour to novel stimuli, showing that variations in stimulus intensity affect behaviour differently from variations in characteristics such as, for instance, visual shape or sound frequency. I argue that such differences can be seen already in how the sense organs react to changes in intensity compared to changes in other stimulus characteristics. I then evaluate a number of models of generalisation with respect to their ability to reproduce intensity generalisation. I reach three main conclusions. First, realistic stimulus representations, based on knowledge of the sense organs, are necessary to account for intensity effects. Models employing stimulus representations too remote from the sense organs are unable to reproduce the data. Second, the intuitive notion that generalisation is based on similarities between stimuli, possibly modelled as distances in an appropriate representation space, is difficult to reconcile with data about intensity generalisation. Third, several simple models, in conjunction with realistic stimulus representations, can account for a wide array of generalisation phenomena along both intensity and non-intensity stimulus dimensions. The paper also introduces concepts which may be generally useful to evaluate and compare different models of behaviour

Chickens prefer beautiful humans

We trained chickens to react to an average human female face but not to an average male face (or vice-versa). In a subsequent test, the animals showed preferences for faces consistent with human sexual preferences (obtained from university students). This suggests that human preferences arise from general properties of nervous systems, rather than from face-specific adaptations. We discuss this result in the light of current debate on the meaning of sexual signals, and suggest further tests of existing hypotheses about the origin of sexual preferences

Discrete conventional signalling of a continuous variable

In aggressive interactions, animals often use a discrete set of signals, while the properties being signalled are likely to be continuous, for example fighting ability or value of victory. Here we investigate a particular model of fighting which allows for conventional signalling of subjective resource value to occur. The result shows that neither perfect nor no signalling are evolutionarily stable strategies (ESSs) in the model. Instead, we find ESSs in which partial information is communicated, with discrete displays signalling a range of values rather than a precise one. The result also indicates that communication should be more precise in conflicts over small resources. Signalling strategies can exist in fighting because of the common interest in avoiding injuries, but communication is likely to be limited because of the fundamental conflict over the resource. Our results reflect a compromise between these two factors. Data allowing for a thorough test of the model are lacking; however, existing data seem consistent with the obtained theoretical results

Spectacular pehnomena and limits to rationality in genetic and cultural evolution

In studies of both animal and human behaviour, game theory is used as a tool for understanding strategies that appear in interactions between individuals. Game theory focuses on adaptive behaviour, which can be attained only at evolutionary equilibrium. Here we suggest that behaviour appearing during interactions is often outside the scope of such analysis. In many types of interaction, conflicts of interest exist between players, fueling the evolution of manipulative strategies. Such strategies evolve out of equilibrium, commonly appearing as spectacular morphology or behaviour with obscure meaning, to which other players may react in non-adaptive, irrational way approach, and outline the conditions in which evolutionary equilibria cannot be maintained. Evidence from studies of biological interactions seems to support the view that behaviour is often not at equilibrium. This also appears to be the case for many human cultural traits, which have spread rapidly despite the fact that they have a negative influence on reproduction