Physiology and Psychophysics – Key Vocabulary

Vocabulary flashcards covering key figures, laws, theories, methods, and concepts from the lecture on the historical development of physiology and psychophysics leading to experimental psychology.

Personal Equation

Observer-specific constant error in measuring reaction times, first noted by astronomers Maskelyne and Bessel.

Bell-Magendie Law

Demonstrates that dorsal spinal roots carry sensory impulses to the brain and ventral roots carry motor impulses from the brain.

Doctrine of Specific Nerve Energies

Johannes Müller’s principle that each sensory nerve produces its own characteristic sensation regardless of how it is stimulated.

Adequate Stimulation

The type of energy to which a sensory receptor is most sensitive; Müller called it “specific irritability.”

Vitalism

View that living organisms possess a non-physical life force beyond chemical and physical processes.

Materialism (in physiology)

Belief that life and mental events can be fully explained by physical and chemical laws; embraced by Helmholtz and colleagues.

Principle of Conservation of Energy

Helmholtz’s demonstration that total energy in organisms is constant—transformed, not created or lost.

Rate of Nerve Conduction

Helmholtz’s measured speed of neural impulse (~27–100 m/s), showing neural transmission is slow and physical.

Unconscious Inference

Helmholtz’s idea that past experience automatically converts raw sensations into meaningful perceptions.

Sensation

The immediate, raw mental effect produced when a sense receptor is stimulated.

Perception

Sensation interpreted and given meaning through unconscious inference and past experience.

Young-Helmholtz (Trichromatic) Theory

Proposes three retinal receptors—red, green, blue-violet—whose combined activity generates all color experiences.

Resonance Place Theory

Helmholtz’s model that specific fibers on the basilar membrane resonate to specific sound frequencies.

Purkinje Shift

Phenomenon where short-wavelength colors appear brighter than long-wavelength colors in dim light.

Hering-Breuer Reflex

Feedback from lung stretch receptors that contributes to regulation of respiration.

Opponent-Process Theory of Color Vision

Hering’s model with paired receptors (red-green, yellow-blue, black-white) operating via anabolic/catabolic processes.

Helmholtz-Hering Debate

19th-century controversy over whether perception is learned (Helmholtz) or innate (Hering).

Evolutionary Theory of Color Vision

Christine Ladd-Franklin’s proposal that achromatic vision evolved first, followed by blue-yellow and then red-green sensitivity.

Phrenology

Gall and Spurzheim’s practice of inferring mental faculties from skull bumps and depressions.

Formal Discipline

Educational view, derived from phrenology, that exercise of a mental faculty strengthens it like a muscle.

Ablation (Extirpation) Method

Flourens’s technique of surgically removing brain parts to infer their functions from behavioral deficits.

Clinical Method

Broca’s approach of correlating clinical symptoms with post-mortem brain lesions.

Broca’s Area

Left frontal-lobe region whose damage impairs speech production (articulation).

Wernicke’s Area

Left temporal-lobe region whose damage impairs speech comprehension.

Motor Cortex

Area discovered by Fritsch and Hitzig where electrical stimulation elicits movements on the contralateral body side.

Two-Point Threshold

Smallest distance at which two simultaneous touches are felt as separate; mapped by Weber.

Just Noticeable Difference (JND)

Smallest detectable change in stimulus intensity; basic unit in Weber’s sensory studies.

Weber’s Law

Ratio stating that JNDs are a constant fraction of the standard stimulus (ΔR/R = k).

Absolute Threshold

Lowest intensity of a stimulus that can be detected at least 50% of the time.

Differential Threshold

Minimum change in stimulus intensity required to produce a JND.

Fechner’s Law

S = k log R; states that sensation magnitude increases logarithmically with stimulus intensity.

Psychophysics

Fechner’s systematic study of quantitative relations between physical stimuli and psychological experience.

Method of Limits

Psychophysical procedure where stimulus intensity is gradually increased or decreased to find thresholds.

Method of Constant Stimuli

Psychophysical technique presenting stimuli of different magnitudes in random order to measure detection or discrimination.

Method of Adjustment

Psychophysical procedure where observers control stimulus intensity until it matches a standard.

Experimental Aesthetics

Fechner’s quantitative study of artistic preference and beauty judgments.

Panpsychism

Fechner’s philosophical belief that all physical things possess consciousness.

Reaction Time Study (Maskelyne & Kinnebrook)

1795 discovery that observers differ systematically in recording star transits, launching study of individual RT differences.

Doctrine of Forward Direction

Bell-Magendie insight that sensory impulses travel into the spinal cord and motor impulses travel outward via distinct nerves.