The science of life : fully illustrated in tone and line and including many diagrams, S. 818

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volume to trace them all—you would find that all the time we were dealing with a directional selective flow through continually radiating associations, a complex journey that would make the course of a message through the most elaborate switchboard of a telephone exchange seem the simplest of processes. Or putting it in language the preceding chapter will have made familiar, you are dealing with a stupendously intricate migration of nerve impulses, of which your idea of “ orange ”’ is not so much a terminus as an important junction and shunting place, starting fresh trains of impulse as soon as one arrives.

The difference between adult human thought and the mental reactions of a dog or monkey, or a very young child, seems to be a difference not in kind but in complexity. A new stage above these animal levels is established by the introduction of words, and a still further stage by the introduction of writing. To evoke the group of associations that constitute orange in a monkey’s mind, one must present some tangible element of the group, the smell of it, or the bowl in which oranges are put, or the sight of someone who is in the habit of giving oranges, or else the creature must feel a hunger and craving that oranges have at some time satisfied. It has our orange junction and shunting yard, but on a much smaller scale. The human mind has developed an unprecedented system of symbols, words; and by means of these tags it can call up and bring together the groups of associations we call ideas in a way that seems to be beyond the power of any other creature. And it can transfer its mental activities to a kindred mind as no animal can do. By superadded systems of symbolism, by drawing and by writing down, the human mind can at the same time fix its ideas for subsequent consideration and free itself from the immediate necessity of attending to them in detail while it explores or develops further associationgroups. We have already discussed the behaviour of the higher mammals and shown that, with the probable exception of some of the higher apes, their mental action hardly ever goes beyond the establishment by trial and disappointment of habits of reaction to the stimulus of particular circumstances. All their learning is the acquisition of habits. The dog or monkey rarely seems to pose the situation, correlate it with memories of previous experiences and bring out of these experiences an idea of appro-

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priate conduct. It is not at that level of mental lucidity. We have, however, described instances of greater deliberation in apes (see Figs. 316, 317). But when we come to the developing human being we find the floundering habitual responses of the dog or monkey giving place more and more to an acuter perception and an exacter response. Which is often less prompt. The higher animal has formed not a habit which goes off almost as automatically as a reflex, but a directive idea.

The development of language has conduced greatly to this process of deliberate and measured response. Words and phrases have come to play the part of handles by which reality can be held off a little and examined. Where the needed responses are invariable the human being will indeed form rigid habits exactly like the responses of a well-trained animal, but there is a great field wherein it is advantageous to vary the response, and then the apparatus provided in verbal and visual symbolization gives the man a versatility altogether beyond the powers of any beast.

The grouped associations, the ideas of things which are gripped together and defined in the human mind by names and other words and symbols, can be subjected, because of these handles, to a searching analysis and can be viewed from this aspect or that. One aspect can be considered, exclusive of others, and so the object can be brought into relation with other things which share some common characteristic. An orange can be thought of as a fruit along with other edible fruits, or as a round thing, along with the earth and a pill and any other round things, or as a yellow golden thing, or as a softish thing, and so on. The human mind can then make general propositions about round things or about yellow golden things. We cannot conceive of any parallel process in a wordless mind.

These general ideas give men quite distinctive powers of producing reactions between this and that group of associations. A young child or an animal has no such general ideas. When a child calls every man it meets “ dada,” or when a dog barks at every stranger, that is not because child or dog possesses general ideas. The child has not generalized from its ““ dada’; it has not yet learnt to distinguish its dada, which is a very different thing. The general ideas of an intelligent adult are the result of a clear discrimination of distinct qualities common to all the items brought under that general idea. The pseudo-