Consciousness

Consciousness is the ongoing awareness of self and surroundings — from focused waking attention to the drifting imagery of dreams.

Levels of consciousness

Consciousness is not simply "on" or "off". Psychologists distinguish several tiers of mental processing:

• Conscious — current awareness; the thoughts and perceptions you are actively attending to.
• Preconscious — information not currently in awareness but easily accessible, such as a memory you can recall on request (e.g. your home address).
• Unconscious / nonconscious — processes outside voluntary awareness (Freud's unconscious; automatic bodily processes like heartbeat and breathing).

Freud argued that unconscious wishes and conflicts influence behaviour indirectly, a claim that shaped psychoanalysis and the study of Defence Mechanisms [blocked]. Modern cognitive science uses "nonconscious" for automatic processing (e.g. skills, priming) without Freud's motivational baggage.

These tiers can be pictured as levels of awareness around the active mind.

Sleep and circadian rhythms

• The circadian rhythm is the roughly 24-hour biological clock, regulated by the suprachiasmatic nucleus (SCN) and the hormone melatonin. The SCN sits in the hypothalamus and responds to light, resetting the clock each day; melatonin released by the pineal gland promotes sleepiness in darkness.
• A sleep cycle lasts about 90 minutes and repeats 4–6 times per night.
• NREM sleep: Stage 1 (light), Stage 2 (deeper), Stage 3 (slow-wave/deep).
• REM sleep — rapid eye movement, vivid dreaming, muscle paralysis; increases later in the night.

During deep NREM (slow-wave) sleep the body repairs tissue and consolidates declarative memories, whereas REM is linked to emotional processing and procedural learning. Disrupting the circadian rhythm — through shift work or jet lag — impairs mood, attention and performance, linking this topic to Attention [blocked].

A single cycle moves down through the NREM stages before REM, then begins again.

Dreams

Theories disagree on why we dream:

• Freud: dreams as disguised wish-fulfilment — manifest content conceals latent meaning.
• Activation-synthesis hypothesis — dreams as the brain's attempt to make sense of random neural activity (Hobson & McCarley); the cortex weaves a story around brainstem signals.
• Information-processing and cognitive views see dreams as a continuation of waking thought, helping consolidate memories and rehearsal of threats.

The three accounts emphasise different sources of dream content.

Sleep disorders

Common sleep disorders include:

• Insomnia (difficulty falling/staying asleep) · narcolepsy (sudden sleep attacks) · sleep apnea (breathing pauses) · sleepwalking · night terrors.

Altered states of consciousness

• Hypnosis — a state of focused attention and heightened suggestibility; useful in some pain and habit-control contexts.
• Meditation — practices that train attention and awareness, associated with reduced stress and improved emotional regulation.
• Psychoactive drugs — substances that cross the blood–brain barrier and change mood, perception or thought:
  • Depressants — alcohol, sedatives (slow the nervous system).
  • Stimulants — caffeine, nicotine, amphetamines, cocaine (increase arousal).
  • Hallucinogens — LSD, psilocybin (distort perception).
  • Opioids — pain relief and euphoria; high addiction risk.

Drug effects involve tolerance (needing more for the same effect), dependence and withdrawal. For the biological basis of these mechanisms, see Biological Basis of Behaviour [blocked].

Key takeaways

• Consciousness ranges from focused waking awareness through preconscious and nonconscious processing.
• The circadian rhythm is a ~24-hour clock run by the SCN and melatonin; sleep cycles last ~90 minutes.
• NREM deep sleep restores the body; REM supports dreaming and memory/emotional processing.
• Freud, activation-synthesis and cognitive views offer competing accounts of dreams.
• Insomnia, narcolepsy, sleep apnea, sleepwalking and night terrors are the main sleep disorders.
• Hypnosis, meditation and psychoactive drugs (depressants, stimulants, hallucinogens, opioids) alter consciousness.

Sources & further reading

• Sleep and sleep disorders — APA
• 4.1 What Is Consciousness? — OpenStax Psychology 2e
• 4.2 Sleep and Why We Sleep — OpenStax Psychology 2e
• 4.4 Sleep Problems and Disorders — OpenStax Psychology 2e