PSYCHOLOGY AND EDUCATION
THE contacts of psychology with education during the twentieth century have been of two main kinds; in the first place along the lines of mental testing and experiment; in the second place along those of psycho-pathology, and especially of psycho-analysis--though these two branches of psychology have very profitably interacted and supported one another at certain points. We have already seen how mental tests arose out of the practical needs of education. As they grew more perfect and more varied, they have been applied to children on an ever larger scale, so that in some places in America children are beginning to know their own "intelligence quotients" almost as a matter of routine. Apart from the measurement of whole school populations, itself of great general interest to both psychology and education, perhaps the greatest practical value of intelligence tests has been found to lie in the diagnosis of cases where a child appears unable to profit from the ordinary school curriculum. The application of a battery of tests in capable hands will, as a rule, show clearly how far the trouble lies in inadequate g, or how far it must be sought for rather in physical defect or functional disturbance. Much the same applies to the case of "difficult" or delinquent children who have given rise to anxiety on account of their general behaviour rather than merely on account of their educational backwardness.
Organized attempts to deal with all cases of these kinds have given rise to two developments of great importance: the