Behavioural factors in the regulation of food intake.

Introduction Mammalian food intake is a discontinuous process, in that feeding runs alternate with non-feeding intervals. These lifelong changes in overt behaviour indicate an underlying organization in which different needs alternately obtain priority. The way in which this channelling of needs might be realized can be investigated by analysing in detail how overt behaviour changes in time. I t is of much importance to know how far food intake behaviour is influenced by the interaction processes involved. Under ad lib. conditions the frequency distribution of the duration of nonfeeding intervals suggests, at least in some species, the existence of meals (Le Magnen & Tallon, 1966; Thomas & Mayer, 1968; Wiepkema, 1968). In these instances food intake depends on factors that determine frequency and size of meals. Probably these meal criteria are not caused by an identical set of causal factors. For instance, food deprivation may enlarge meal size without influencing the number of daily meals (Wiepkema, 1968), whereas caloric dilution of the diet may have just the reverse effect (Le Magnen, 1969). The factors that determine exactly meal frequency will not be discussed here. They may be very difficult to unravel, since circadian processes also contribute to the distribution of meals during a 24 h period (Le Magnen & Devos, 1970).