AP Psychology Study Notes: From Sensation to Conscious Awareness

Sensation

The process by which sensory receptors and the nervous system receive and represent stimulus energy from the environment.

Perception

The process of organizing and interpreting sensory information so you can recognize meaningful objects and events.

Transduction

Conversion of one form of energy (light, sound waves, pressure, etc.) into neural impulses by sensory receptors.

Absolute threshold

The minimum stimulus intensity needed to detect a stimulus 50% of the time.

Difference threshold (Just Noticeable Difference, JND)

The minimum difference between two stimuli required to detect a change 50% of the time.

Weber’s law

For many senses, the JND is a constant proportion of the original stimulus intensity (ΔI/I = k), not a constant absolute amount.

Sensory adaptation

Decreased sensitivity after constant stimulation (e.g., you stop noticing a persistent smell).

Rods

Retinal receptors best for dim light and peripheral vision; they do not detect color and provide lower acuity (detail).

Cones

Retinal receptors best for bright light, color vision, and fine detail; densely packed in the fovea and provide higher acuity.

Trichromatic theory

Color vision theory stating the retina contains three types of cones sensitive to different wavelengths (commonly described as red, green, and blue) whose combined activity produces color perception.

Opponent-process theory

Color is processed in opposing pairs (red–green, blue–yellow, black–white); helps explain afterimages via opponent activity after fatigue.

Place theory

Pitch theory proposing that different pitches activate different places along the cochlea (especially accurate for high frequencies).

Frequency theory

Pitch theory proposing that the rate of auditory nerve impulses matches the frequency of the sound wave (best for low frequencies).

Selective attention

Focusing on one stimulus or task while filtering out other incoming information due to limited cognitive resources.

Inattentional blindness

Failing to notice a visible stimulus because attention is directed elsewhere.

Change blindness

Failing to notice changes in a scene when attention is disrupted (e.g., by a brief interruption).

Signal detection theory

Explains detection as a decision process influenced by stimulus strength plus factors like alertness/fatigue, motivation, and expectations (bias).

Gestalt principles

Rules by which the brain organizes sensory input into meaningful wholes (e.g., figure-ground, proximity, similarity, continuity, closure).

Perceptual constancy

The tendency to perceive objects as stable despite changing sensory input (e.g., size constancy and shape constancy).

Circadian rhythms

Roughly 24-hour biological cycles that influence sleepiness, alertness, body temperature, and hormone release; regulated strongly by light.

NREM-3 (slow-wave sleep)

Deep sleep stage with large, slow brain waves; associated with physical restoration and more likely to involve sleepwalking and night terrors.

REM sleep

Sleep stage marked by rapid eye movements, vivid dreaming, brain activity similar to wakefulness, and muscle atonia (protective paralysis).

Psychoactive drugs

Chemicals that alter perceptions and mood by affecting neurotransmitter systems; common categories include depressants, stimulants, hallucinogens, and opioids (opiates).

Tolerance

Needing more of a drug to achieve the same effect.

Withdrawal

Physical and psychological discomfort experienced when stopping a drug.