Donald Hebb was one of the most influential psychologists of the 20th century and the first version of this textbook was written in 1958. This 4th edition, co-authored with Donderi, was originally published in 1987 and the object of the book was to introduce the student to the scientific study of the human mind and behaviour. The authors' concern was with scientific psychology and fundamental principles. They felt this understanding was the best preparation to following future developments in psychological knowledge and to understand the changes in how that knowledge was applied. Although psychology has developed in many directions since its publication, much of the information in this book is still relevant today.