Models of the World in the Brain: Some Speculations

Peter Hillman


A critical component of survival is the ability to predict the response of the environment - especially, but not only, that of other creatures - to our actions.  This prediction is an essential part of the decision-making process.  Prediction of course does not have to be conscious, and does not require consciousness – animals, even “lower” animals, are constantly making decisions based on predictions as to the results of their behaviour.  Probably most of our own decisions are based on unconscious prediction that may not even be accessible to consciousness. 


In order to make such prediction, one must have some kind of internal model of the world.  This internal model has to contain and obey the physical laws of our environment, and at least part of this “knowledge” may be genetic, or have a genetic infrastructure.  Even in the “lowest” animals, however, the model also includes the “self” in the sense that it covers the genetically programmed responses of the body to various stimuli.


The most primitive learned elaboration of this model would be little more than an accumulation of associative memories.  These memories constitute unconscious predictions – manifested in bodily responses - as to the significance of stimuli beyond that genetically programmed. 


Such models probably exist in the brains of "lower" animals such as reptiles, insects and some birds.  These models may not be simple, and may include (as for birds and bees) learned maps of the environment with salient features and their significance.  There is evidence that in some birds, and probably bees too, the maps may be multi-sensory, containing, in addition to visual cues, cues of smell and perhaps even magnetic fields (in bird migration and homing). 


However, the models seem not to be "contingent" - the animal is not able to ask "what if...?".  In a sense, the models are not "interactive".  They do not allow the animal to evaluate the results of possible alternative behaviours.  


Such interactive models certainly exist, to a greater or lesser degree, in "higher" animals.  But it seems that only in humans do the models become "complete":  A "complete" model is a replica of the world, and includes the acquired significance of all its components – emotional, cultural and social.  The model requires a degree of empathy – a “theory of mind”, or an understanding of the minds of others – “I think that you believe that he knows that…” which in humans reaches something like the fifth degree, in animals much less.  Theory of mind is the ability to attribute mental states – beliefs, intents, desires, pretending, knowledge, etc. – to oneself and others.  It enables one to understand that mental states can be the cause of – and thus be used to predict – others’ behaviour.  (The existence and nature of a theory of mind in animals is the subject of debate, and the development of a theory of mind in children is the fascinating subject of much study.)


The replica makes it possible for us to “try out” all possible behaviours – including verbal communication, of course – in order to decide in advance what behaviour will most enhance our welfare or minimise harm.

The replica is interactive, in the sense that the rehearsal of the effects of possible behaviours involves prediction of the responses of the environment, and in particular of other individuals, to our actions or words. 


The ability to understand the minds of others has recently been given a (partial?) physiological basis through the discovery of “mirror” cells in the brains of monkeys and apparently of humans (see Rizzolatti et al., “Mirrors in the Mind”, Scientific American, November 2006).  These cells respond in the same way to the actions and emotions of others as to the actions and emotions of the self, thereby providing a possible neural infrastructure for empathy and a theory of mind, and enabling us to understand and predict the behaviour of others.   Malfunction of these cells may be related to autism (see Ramachandran and Oberman, “Broken Mirrors:  A Theory of Autism”, Scientific American, November 2006).


The existence of such a “complete” replica seems to be the, perhaps inevitable, completion of an evolutionary process and may be related to that most mysterious of human characteristics – consciousness.


September 2007

Peter Hillman holds a Ph.d. in nuclear physics from Harvard University. In 1959 he joined the physics department of the Weizmann Institute of Science. From 1963 till 1967 he served as the head of that department. In 1969 he joined
the Hebrew University as the head the department of Neurobiology, till 1995. During the 80-ties he initiated the
science museum in Jerusalem, at first as a department inside the Hebrew University, later to become
an independent institute. Since then Peter hold a position in the museum, at first as the head of the museum, and later as a scientific director.

Models: Between Science and Art, November 2007