What goes on in this interval between the advent of the incoming nerve process and the discharge of the outgoing nerve process?
Something, at any rate, which represents a brain process of great complexity.

Now, anything that fixes or simplifies the brain process, in so far gives greater certainty to the results.

For this reason experiments on reflex actions are valuable and decisive where similar experiments on voluntary actions are uncertain and of doubtful value.
Now the child's mind is relatively simple, and so offers a field for more fruitful experiment; this is seen in the reactions of the infant to strong stimuli, such as bright colours, etc., as related further on.
With this inadequate review of the advantages of infant psychology, it is well also to point out the dangers of the abuse of it.

Such dangers are real.

The very simplicity which seems to characterize the life of the child is often extremely misleading, and this because the simplicity in question is sometimes ambiguous.