The Mechanism of an Instinctive Control System: a Hypothesis

This paper provides a formal characterisation of an Instinctive Control System, and presents a new hypothesis about its mechanism. The hypothesis is based on findings in human behaviour made by the psychoanalytic technique, but applies directly to lower anima's and has many implications for ethology. The problem of phantasy in human behaviour is discussed. This problem is perfectly objective, and the term 'phantasy', like others in psychoanalysis, stands for a central nervous mechanism postulated to account for observed overt behaviour, verbal and otherwise. Two kinds of phantasies are distinguished-Hallucinations, acute central nervous processes potentially having a formally identical effect on overt behaviour with that of corresponding receptor inputs, but not in fact so derived; and Pretences, chronic central nervous processes describable as 'false messages' and tending over long periods to produce inadaptive overt behaviour. The hypothesis of VON HOLST and MITTELSTAEDT (Das Reafferenzprinzip) is briefly reviewed. They have demonstrated that messages can be generated in the central nervous system of man and other animals whose effect on behaviour is formally identical with that of messages derived from immediately previous receptor inputs, though they are not in fact so derived. We suggest that their 'Output Copy' (Efferenzkopie) is a special case of a general class of messages with such properties to which we have given the name of 'Prosensory Input' (PSI). Certain formal properties are ascribed to central nervous mechanisms in terms of which they can be classified (operationally) as a graded series with greater or less degree of 'instinctiveness', which by this means is given a precise definition. The mechanisms near the higher end of the scale in respect of this property are arbitrarily called 'Instinctive'. This definition is independent of the distinction of innate and learned, and precisely expresses such intuitively recognised properties of Instinctive Centres as 'accumulation' and 'release'. A hypothesis about the mechanism of an Instinctive Control System so characterised is put forward. It is proposed that an I.R.M. consists of a set of units of various properties, the essential assumption being that when the I.R.M. is activated by input from elsewhere in the C.N.S., Pro-Sensory Input (PSI) is set up having the same formal characteristics as the Key Stimuli for the same I.R.M. This PSI in combination with the Key Stimulus inputs produces a definite simple quantitative output from the I.R.M. The formulation takes account of the product relation between Internal and External Factors and of the law of Heterogeneous Summation. The formulation is now applied to an arbitrarily simplified system of Instinctive Centres and I.R.M.s, certain definite properties and connections being postulated. When the output from a given I.R.M. reaches a certain fixed quantity, the immediately superordinated Centre is inhibited: this leads to stoppage of the current level of appetitive behaviour and release of the Centre corresponding to the I.R.M. This critical output quantity will not normally be attained without the contribution of Key Stimuli, but in certain cases this contribution need only be very small, PSI alone sufficing for release. Various refinements are suggested. Until the consummatory act is finally released, another system of PSI is continuously active, and leads to 'accumulation' by means of a system of self-reexciting circuits which fire an increasing quantity of excitation back into the whole system the longer they are stimulated. 'Accumulation' can continue because the Centres of lower level are inhibited by their superordinates. This process stops when certain receptor inputs result from performance of the consummatory act, the accumulator system then 'running down' in a manner dependent on the previous accumulation. The PSI just referred to is formally identical with these 'feedback' inputs, and is referred to as feedback PSI. The hypothesis is applied to various problems of lower animal ethology. It accounts for the phenomena of accumulation and exhaustion, though other factors may play a part. It has formal advantages over previous hypotheses in accounting for the phenomena of displacement activities, about whose function and evolution a new view is put forward. It can be modified to take account of hierarchical and other complexities, and may be applied to all grades of Releasing Mechanisms from fully innate to wholly learned, supplying a new interpretation of 'learned rewards'. Not only does it predict vacuum activities, for which a biological definition is here put forward, but also 'vacuum inactivity', difficult to demonstrate in lower animals but of great importance in human behaviour. This occurs when feedback PSI alone reaches a critical level for stopping accumulation, or even throwing it 'into reverse'. This postulated process, which will lead to complete cessation of any appetitive behaviour autochthonous to the system without performance of the consummatery act, is used as an objective definition of the term 'phantasy of gratification'. Other subjective terms are similarly redefined. Finally, it is stressed that the above hypothesis refers only to those mechanisms referred to by CRAIG as 'appetites' (e.g. not to the mechanism for escape). The problem of neurosis is that of the perpetuation of disturbance in behaviour after removal of the disturbing stimulus. We believe this effect in man to be due to the setting up of Pretences. General considerations about primate evolution, and especially the theory of CHANCE and MEAD, suggest the mode of origin of such a general mechanism. By applying our hypothesis to situations of conflict in infancy, and postulating that repetition of similar conflicts leads to a repeated occurrence in combination of displacement activity and 'phantasy of gratification', we are able to show that the operation of this mechanism is formally analogous to that of ordinary reward learning. Pretences set up in this way perpetuate inappropriate behaviour and also lead continually to further pretences. Other clinical implications are discussed.