Psychophysiology

The study of relationships between psychological processes and bodily measurements. In emotion research it combines self-report, behavior and physiological recordings; agreement among these measures is an empirical question.

Statistical classification of emotion categories using measurements of the autonomic nervous system. It requires an independently justified target label, appropriate cross-validation, and evaluation in the population and context where the classifier will be used. Predictive success does not imply that every instance of a category has one invariant physiological pattern.

Fix a true-positive probability $s>0$ and false-positive probability $f>0$. The positive predictive value at base rate $p$ is $v(p)=sp/(sp+f(1-p))$. Differentiation gives $v^{\prime }(p)=sf/[f+(s-f)p{]}^2>0$, while $v(p)\to 0$ as $p\to 0$. Thus a classifier can retain the same conditional performance yet become unreliable among its positive classifications when the target emotion is rare. This is a mathematical implication of the specified binary model, not an empirical performance estimate.

Changes in the electrical properties of skin associated with sweat gland activity. Recording electrodes can measure tonic levels and event-related changes in skin conductance. Such changes inform psychophysiology but do not uniquely identify an emotion.

The electrical conductance of skin, often measured between two recording electrodes. Sweating changes the conductive properties of the skin. Baseline, movement and recording conditions must be considered before interpreting an event-related response as evidence about emotion.

A researcher whose work includes facial electromyography and responses to facial expressions.^[ref]

A researcher in psychophysiology whose work includes variation in autonomic responses during emotion.^[ref]