5.5 SUMMARY

• Consciousness is a mystery of psychology because other people’s minds cannot be perceived directly and because the relationship between mind and body is perplexing.
• Consciousness has four basic properties: intentionality, unity, selectivity, and transience. It can also be understood in terms of three levels: minimal consciousness, full consciousness, and self-consciousness.
• Conscious contents can include current concerns, daydreams, and unwanted thoughts.
• The cognitive unconscious is at work when subliminal perception and unconscious decision processes influence thought or behavior without the person’s awareness.

• During a night’s sleep, the brain passes in and out of five stages of sleep; most dreaming occurs in the REM sleep stage.
• Sleep needs decrease over the life span, but being deprived of sleep and dreams has psychological and physical costs.
• Sleep can be disrupted through disorders that include insomnia, sleep apnea, somnambulism, narcolepsy, sleep paralysis, and night terrors.
• fMRI studies of the brain in dreaming reveal increased activity in brain areas associated with visual imagery and emotions such as fear, and decreased activity in brain areas associated with planning and in suppression of movement.

• Psychoactive drugs influence consciousness by altering the effects of neurotransmitters.
• Drug tolerance can result in overdose, and physical and psychological dependence can lead to addiction.
• Major types of psychoactive drugs include depressants, stimulants, narcotics, hallucinogens, and marijuana.
• The varying effects of alcohol, a depressant, are explained by theories of alcohol expectancy and alcohol myopia.

• Hypnosis is an altered state of consciousness characterized by suggestibility.
• Although many claims for hypnosis overstate its effects, hypnosis can create the experience that one’s actions are occurring involuntarily, create analgesia, and even change brain activations in ways that suggest that hypnotic experiences are more than imagination.