Sensory contexts linked to actions

From A conversation about the brain
Jump to: navigation, search
A simple organism moves toward sugar, grows, moves toward chemical B then splits. Three signals (sugar, chemical B and mass) are involved and two modes of behaviour. Same as above but as animated slides.
Consider a simple, single-celled organism. It first crawls towards and absorbs sugar, grows larger then changes its behaviour. Now it crawls towards chemical B: when it has absorbed sufficient of this the organism splits into two and its life cycle begins again. This can be considered as very similar to two short phases of a complex activity in a human, e.g. as accomplished during two periods of fixation (which typically last 1/3 of second each. In Land's study of tea-making[1] it takes 300 fixations to make a cup of tea (as you can see here) and the tea-maker's behaviour is determined by one or two visual parameters during each period of fixation. The similarity between the two cases is that the current sensory+motivational context is recognised, it results in a motor output and hence a new sensory+motivational context, and so on. The key difference between the two is the dimensionality of the space involved. In the case of the amoeba, only three dimensions were required. To make tea, it takes many more. A very low-dimensional hyperplane describes the relevant changing parameters while a very large number of dimensions define the current context (e.g. the observer is making a cup of tea in a certain kitchen, the kettle has not yet boiled, etc).

To run a Matlab script that illustrates this but on the surface of a 3D sphere (3 dimensions are mass, gradient of sugar and gradient of chemical B), you can download the files here:

main.m step_amoeba.m get_unit_r.m. get_unit_wr.m. show_sphere.m.

To view a video of the Matlab script being run, please click here:

Video Amoeba


  1. Land, M. F., Mennie, N., & Rusted, J. (1999). Eye movements and the roles of vision in activities of daily living: making a cup of tea. Perception, 28(4), 1311-1328