MCAT Psychology & Sociology - Core Concepts

Front

Absolute threshold vs. difference threshold (just noticeable difference)

Back

Absolute threshold is the minimum stimulus intensity needed for detection 50% of the time. Difference threshold (JND) is the smallest detectable change in stimulus intensity. Weber's Law states that JND is proportional to the original stimulus intensity: ΔI/I = k, where k varies by sense.

Front

Signal detection theory: What are hits, misses, false alarms, and correct rejections?

Back

Hit: signal present, observer says 'yes.' Miss: signal present, observer says 'no.' False alarm: signal absent, observer says 'yes.' Correct rejection: signal absent, observer says 'no.' Response bias (criterion) affects these rates independently of sensitivity (d').

Front

Sensory adaptation and its implications for perception

Back

Sensory adaptation is the diminished sensitivity to constant stimuli over time. Receptor cells reduce firing rates when stimulation is unchanging. This explains why you stop noticing your clothes after putting them on. It allows organisms to detect changes rather than constant conditions.

Front

Top-down vs. bottom-up processing in perception

Back

Bottom-up processing: perception builds from sensory input to higher-level interpretation (data-driven). Top-down processing: prior knowledge, expectations, and context shape perception (conceptually-driven). Reading relies heavily on top-down—you can decode misspelled words using context.

Front

Gestalt principles of perceptual organization

Back

Key principles: Proximity (nearby items grouped together), Similarity (similar items grouped), Continuity (perceive continuous patterns), Closure (fill in gaps), Figure-ground (distinguish object from background). These innate organizing tendencies help construct meaningful perceptions from fragmented input.