Babbling -  A producton of sounds that resemble many different languages.

Basal metabolic rate -  The rate at which energy is used when a person is at complete rest.

Basilar membrane -  A membrane in the inner ear that runs along the length of the cochlea.

Behavior genetics -  The study of behavior and personality differences among people.

Behavior therapies -  Treatments involving complex conversations between therapists and clients that are aimed at directly influencing maladaptive behaviors through the use of learning principles.

Belief perseverance -  The process of rejecting evidence that refutes one’s beliefs.

Benzodiazepines -  A class of antianxiety drugs. They are also called tranquilizers.

Beta waves -  The type of brain waves present when a person is awake and alert.

Bias -  The distortion of results by a variable that is not part of the hypothesis.

Big Five -  Five basic personality traits from which other traits are derived. They include neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness.

Binocular cues -  Depth perception cues that require both eyes.

Biological rhythms -  Periodic physiological changes.

Biomedical therapies -  Treatments that involve efforts to directly alter biological functioning through medication, electric shocks, or surgery.

Biopsychosocial model of illness -  The idea that physical illness is the result of a complicated interaction among biological, psychological, and sociocultural factors.

Bipolar disorders -  Disorders in which people alternate between periods of depression and mania.

Blood-brain barrier -  A membrane that lets some substances from the blood into the brain but keeps out others.

Borderline personality disorder -  A disorder characterized by impulsive behavior and unstable relationships, emotions, and self-image.

Brain -  The main organ in the nervous system.

Brain waves -  Tracings that show the electrical activity of the brain.

Broca’s area -  A part of the brain, in the left frontal lobe, that is involved in speech production.

Bulimia nervosa -  A disorder involving binge eating followed by compensatory behaviors such as vomiting, fasting, excessive exercise, or use of laxatives, diuretics, and other medications to control body weight.

Bystander effect -  The tendency of people to be less likely to offer help to someone who needs it if other people are also present.