Study Guide: Psychophysics, Weber’s Law & Sensory Thresholds

Vocabulary flashcards covering the mathematical formulations of Weber's Law, types of sensory thresholds, and factors influencing sensory detection based on psychophysics principles.

Psychophysics

The branch of psychology that investigates the quantitative relationships between physical stimuli and psychological sensations.

Absolute Threshold

The minimum physical stimulus intensity required for detection $50\%$ of the time.

Difference Threshold (Just Noticeable Difference / JND)

The minimum change in stimulus intensity ($\Delta I$) required to perceive a difference between two stimuli $50\%$ of the time.

Weber's Law Equation

$$\frac{\Delta I}{I} = k$$

Weber Constant ($k$)

A fixed ratio unique to each sensory system, calculated by dividing the threshold change ($\Delta I$) by the baseline intensity ($I$).

Graphical Representation of Weber's Law

A plot of background intensity ($I$) on the x-axis against incremental threshold ($\Delta I$) on the y-axis, yielding a straight line with slope $k$.

Motivation

A psychological factor where high motivation (e.g., financial reward or threat avoidance) decreases the numerical threshold, allowing weaker stimuli to be detected.

Alertness

A physiological factor where higher vigilance or alertness decreases the threshold, increasing sensory sensitivity.

Sensory Adaptation

A decrease in sensory sensitivity (increase in threshold) following prolonged exposure to a constant stimulus.

Subliminal Stimulus

A stimulus intensity falling below the absolute threshold (detected less than $50\%$ of the time).

Superliminal Stimulus

A stimulus intensity resting above the absolute threshold (detected more than $50\%$ of the time).