"Modelling natural action selection"

Introduction to the Special Issue "Modelling natural action selection"
Philosophical Transactions of the Royal Society London B
September 2007

A special issue containing fourteen papers on various aspects of modelling action selection in animals and humans. There are multiple methods in the study of biological action selection ("of deciding 'what to do next'"), each approaching the problem from different points of view: be it ethology or psychology studying the biological systems, or artificial intelligence or artificial life attempting to build artefacts based on the biological principles. These differing approaches may be characterised by distinguishing between the analytical and synthetic methods in the behavioural and brain sciences, as proposed by Braitenberg.

The analytical method seeks to describe transitions in behaviour (and to explain why they occur in any given context), either functionally through reference to some concept of utility, or mechanistically through reference to underlying neural systems. It is at the overlap between these two approaches that modelling (the "synthetic" approach - the creation of artificial systems which behave as natural ones) has an increasing influence: "what would it take to build a system that acts in this way?" It is not only formal mathematical models which are of interest, but also, and in cooperation, simulations for which mathematical solutions are intractable or unknown. This usually consists of extracting desired properties to be reproduced through observation, and their characterisation using tools from more traditional experimental sciences. In this way, novel hypotheses may be developed, and empirical data may be analysed from the perspective of the simulation model.

In creating models of action selection (and of other models of biological functioning), there are four important questions which need to be addressed and which should also be bourne in mind during development (quote from paper): "...is the model sufficiently constrained by biological data that its functioning can capture interesting properties of the natural system of interest? Do manipulations of the model, intended to mirror scientific procedures or observed natural processes, result in similar outcomes to those seen in real life? Does the model make predictions? Is the model more complex than it needs to be in order to describe a phenomenon, or is it too simple to engage with empirical data?" Concerning this last question, there is then a trade-off between simplicity for the purposes of analysis and adequate complexity for a sufficient model of the process(es) in question, neither extreme of which is suitable.

The introductory paper (by Prescott, Bryson and Seth) summarises the eight main areas covered by the special issue contributors (optimality of action selection, cortical-basal ganglia substrates, behavioural sequencing, subcortical substrates, disorders, perceptual selection, units of selection, and action selection in social contexts) and provides a discussion of modelling strategies and techniques in general. I hope to summarise a few of these papers in the coming weeks (particularly Botvinicks paper on a model of Fusters 'hierarchies').

Contents of special issue, here. Unfortunately, all of the papers are available by subscription only.

- Introduction. Modelling natural action selection TJ Prescott, JJ Bryson and AK Seth
- Do we expect natural selection to produce rational behaviour? AI Houston, JM McNamara and MD Steer
- The ecology of action selection: insights from artificial life AK Seth
- Compromise strategies for action selection FL Crabbe
- Action selection and refinement in subcortical loops through basal ganglia and cerebellum JC Houk, C Bastianen, D Fansler, A Fishbach, D Fraser, PJ Reber, SA Roy and LS Simo
- Cortical mechanisms of action selection: the affordance competition hypothesis P Cisek
- Towards an executive without a homunculus: computational models of the prefrontal cortex/basal ganglia system TE Hazy, MJ Frank and RC O'Reilly
- Multilevel structure in behaviour and in the brain: a model of Fuster's hierarchy MM Botvinick
- Is there a brainstem substrate for action selection? MD Humphries, K Gurney, and TJ Prescott
- Understanding decision-making deficits in neurological conditions: insights from models of natural action selection MJ Frank, A Scheres and SJ Sherman
- Extending a biologically inspired model of choice: multi-alternatives, nonlinearity and value-based multidimensional choice R Bogacz, M Usher, J Zhang and JL McClelland
- Biologically constrained action selection improves cognitive control in a model of the Stroop task T Stafford and KN Gurney
- Agent-based modelling as scientific method: a case study analysing primate social behaviour JJ Bryson, Y Ando and H Lehmann
- An agent-based model of group decision making in baboons WI Sellers, RA Hill and BS Logan
- Spatial models of political competition with endogenous political parties M Laver and M Schilperoord