Psychology is the science of the intellects, characters and behavior of animals including man. Human education is concerned with certain changes in t… - Edward Thorndike

Psychology helps to measure the probability that an aim is attainable. For example, certain writers about education state or imply that the knowledge and skill and habits of behavior which are taught to the children of today are of service not only to this generation and to later generations through the work this generation does, but also to later generations forever through the inheritance of increased capacity for knowledge and skill and morals. But if the mental and moral changes made in one generation are not transmitted by heredity to the next generation, the improvement of the race by direct transfer of acquisitions is a foolish, because futile aim.

The intellectual evolution of the race consists in an increase in the number, delicacy, complexity, permanence and speed of formation of such associations.

If we (researchers) should keep the environment of boys and girls absolutely similar these instincts would produce sure and important differences between the mental and moral activities of boys and girls.