Any abnormality in the tissue of an organism, usually caused by disease or trauma.
Psychology and the Brain
Psychology is commonly defined as the scientific study of
behavior and mental processes. It has existed since the late 19th
century, with 1879 often being given as a starting date because that was when
the first psychological research lab was founded. Many schools of thought
within the field have come and gone since then; some, like behaviorism, have persisted and evolved if they
stood up to scientific study; others, like phrenology, have faded as they have lost credibility.
One approach has only begun to gain ground over the
20th and 21st centuries as scientific research and technology have improved: the study of the brain. Neuroscience is a relatively new field, but
the more research that is done, the more it appears that much of human behavior
and mental processes—the key interests for psychological study—are intimately
intertwined with activity in the brain. Understanding the brain is important no
matter what type of psychology you will be involved with, because its
effects permeate all human behavior.
Studying damaged brains is one of the most useful ways to increase our understanding of the links between the brain and behavior. A lesion is a general term for any abnormality in tissue, usually caused by disease or trauma. Lesions are important to the study of brain and behavior because if a psychologist sees a person with a partially damaged brain and then sees changes in that person’s behavior, those behavioral changes can often be attributed to the brain damage. For example, damage to a part of the brain called Broca’s area causes patients to lose the ability to speak; knowing this, we can infer that that part of the brain is in some way related to language production. This gives us more information about neuroanatomy and also about the influence the brain has on behavior.
Dualism is the
idea that the mind and the body are two separate entities. Since the body is a
physical entity and the mind is not, for many centuries philosophers (and
later, psychologists) usually operated under the assumption that the body and
the mind were of different kinds of substance. Rene Descartes famously
theorized that the mind and body were separate, since he could doubt that he
had a body because he might be dreaming, but he could not doubt that he had a
mind since something was doing the doubting. Thus, the central claim of what is
called Cartesian dualism is that the mind and the body are two separate
substances that interact.
There is an ongoing debate today over whether the mind and body are separate
materials, or whether consciousness can arise from purely physiological
processes. This is known in psychology, cognitive science, philosophy, and
artificial intelligence as the hard problem of consciousness.