Dogs get lost hundreds of times and no one ever notices it or sends an account of it to a scientific magazine.

To the intelligent man with an interest in human nature it must often appear strange that so much of the energy of the scientific world has been spent on the study of the body and so little on the study of the mind.

Human beings are accustomed to think of intellect as the power of having and controlling ideas and of ability to learn as synonymous with ability to have ideas. But learning by having ideas is really one of the rare and isolated events in nature.

The restriction of studies of human intellect and character to studies of conscious states was not without influence on a scientific studies of animal psychology.

The real difference between a man's scientific judgments about himself and the judgment of others about him is he has added sources of knowledge.

Nowhere more truly than in his mental capacities is man a part of nature.

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