118 INTELLIGENT BEHAVIOUR 
with increased energy, he affords evidence of selection based 
on individual experience. And such selection implies intelli- 
gence in almost its simplest expression. We may say, there- 
fore, that, whereas instinctive behaviour is prior to individual 
experience, intelligent behaviour is the outcome and product 
of such experience. This distinction is presumably clear 
enough ; and it is one that is based on the facts of observa- 
tion. But we must not fail to notice that, though the logical 
distinction is quite clear, the acquired modifications of be- 
haviour, which we speak of as intelligent, presuppose congenital 
modes of response which are guided to finer issues. We may 
say, then, that where these congenital modes of response take 
the form of instinctive behaviour, there is supplied a general 
plan of action which intelligence particularizes in such a 
manner as to produce accommodation to the conditions of 
existence. 
We have already frankly admitted that, in the present state 
of our knowledge, we do not know with any definiteness how 
intelligent modification of behaviour is effected. But it seems 
probable that from all parts of the automatically working 
organic machine messages come in to the centres of conscious 
control, and that in accordance with the net result of all these 
messages, past and present, tinged with pleasure or pain, other 
messages go out to the automatic centres, and, by checking 
their action here and enforcing it there, give new direction to 
the resulting behaviour. If this be so, the consciousness 
associated with the control-centres is like the person who sits 
in a central office and guides the working of some organized 
system in accordance with the information he is constantly 
receiving ; who sends messages to check activity in certain 
directions and to render it more efficient and vigorous in 
others. 
It may be said, however, that intelligent guidance is, at any 
rate in such simple cases as the selection of a palatable grub 
and the rejection of a nauseous ladybird, itself determined by 
instinctive likes and dislikes. All young chicks apparently 
find wasp-larve palatable and ladybirds the reverse; and 
