The neural processes underlying filial imprinting in birds are divided
, for purposes of theoretical analysis, into three systems: Analysis o
f stimuli into features, Recognition of familiar stimuli in terms of t
heir features and Execution of filial behaviour. The Analysis system i
s linked to the Recognition system which is linked, in turn, to the Ex
ecutive system; the Analysis system is also linked directly to the Exe
cutive system. Each system consists of modules that contain units. The
neural net, used to explore this model, is unsupervised and three-lay
ered; and it is fast since it can operate efficiently with few modules
. In the naive state, the strengths of the connections between units i
n one system and those in others downstream art all low, with the exce
ption of those connections between units in the Analysis and Executive
systems; these connections art started at maximum strength. Connectio
ns between active units of two systems are strengthened up to a maximu
m; those between an inactive unit of one system and an active unit in
a system downstream are weakened down to zero. Weakening takes place m
ore slowly than strengthening. This model simulates many aspects of im
printing including recognition of fine detail in the familiar stimulus
, while generalizing to stimuli resembling the one with which the bird
was imprinted. When experienced, the model simulates withdrawal from
objects that are sufficiently novel and, as a consequence, the end of
the sensitive period for imprinting. The model readily forms polymorph
ous categories, updates existing stimulus representations and classifi
es together physically distinct stimuli, if they have occurred within
a short time of each other.