The mysteries of the human mind and human behavior have been a source of
fascination and speculation throughout recorded history, and surely, for a long
time before that. Attempts to explain human thoughts, emotions, and behavior,
especially when they are disordered, go back just as long; and have often involved
magic, evil spirits, invisible entities, and such unusual ideas as stones in
the head and memories of previous lives. The scientifi c fi eld of psychology is
less than 150 years old. Most textbooks date its beginning to the establishment
of Wilhelm Wundt’s laboratory in Leipzig, Germany, in 1879. Since that time
the fi eld has grown rapidly, and the application of scientifi c method has led to
many remarkable discoveries about how the human brain and mind actually
work, along with what actually determines human behavior.