How should biological behaviour be modelled? A relatively new approach is to investigate problems in neuroethology by building physical robot models of biological sensorimotor systems. The explication and justification of this approach are here placed within a framework for describing and comparing models in the behavioural and biological sciences. First, simulation models – the representation of a hypothesis about a target system – are distinguished from several other relationships also termed “modelling” in discussions of scientific explanation. Seven dimensions on which simulation models can differ are defined and distinctions between them discussed:

1. Relevance: whether the model tests and generates hypotheses applicable to biology.

2. Level: the elemental units of the model in the hierarchy from atoms to societies.

3. Generality: the range of biological systems the model can represent.

4. Abstraction: the complexity, relative to the target, or amount of detail included in the model.

5. Structural accuracy: how well the model represents the actual mechanisms underlying the behaviour.

6. Performance match: to what extent the model behaviour matches the target behaviour.

7. Medium: the physical basis by which the model is implemented.

No specific position in the space of models thus defined is the only correct one, but a good modelling methodology should be explicit about its position and the justification for that position. It is argued that in building robot models biological relevance is more effective than loose biological inspiration; multiple levels can be integrated; that generality cannot be assumed but might emerge from studying specific instances; abstraction is better done by simplification than idealisation; accuracy can be approached through iterations of complete systems; that the model should be able to match and predict target behaviour; and that a physical medium can have significant advantages. These arguments reflect the view that biological behaviour needs to be studied and modelled in context, that is, in terms of the real problems faced by real animals in real environments.