The Psychic Life of Micro-Organisms: A Study in Experimantal Psychology

From the preface when this work was originally published in 1888: "I have endeavored, in the following essay upon Micro-organisms, to show that psychological phenomena begin among the very lowest classes of beings; they are met with in every form of life from the simplest cellule to the most complicated organism. It is they that are the essential phenomena of life, inherent in all protoplasm."
French psychologist Alfred Binet (1859-1911) took a different tack than most psychologists of his day: he was interested in the workings of the normal mind rather than the pathology of mental illness. He wanted to find a way to measure the ability to think and reason, apart from education in any particular field. From Binet's work, the phrase "intelligence quotient," or "IQ," entered the vocabulary.