Stress

Stress in the context of cognitive monitoring refers to the physiological and psychological response to perceived demands that approach or exceed an individual's perceived coping resources. Unlike cognitive workload - which captures objective mental resource utilisation - stress involves subjective appraisal and emotional reactivity.

Stress vs. Workload

These two states are related but distinct:

Stress and workload interact: high workload triggers acute stress when the operator perceives that they may not cope; sustained stress impairs cognitive capacity and increases apparent workload.

The Valence–Arousal Framework

Stress is commonly modelled in a two-dimensional affective space:

• Valence - the pleasantness/unpleasantness of the emotional state (positive to negative).
• Arousal - the intensity or activation level of the state (calm to excited).

Stress occupies the high arousal, negative valence quadrant. This two-dimensional representation allows continuous tracking of emotional state rather than forcing a binary "stressed/not stressed" classification.

The Self-Assessment Manikin (SAM) is the standard instrument for collecting valence and arousal ratings, using pictographic 9-point scales that are accessible across languages and cultures.

Physiological Correlates

EEG

Autonomic Nervous System

Stress produces strong autonomic signatures via sympathetic nervous system (SNS) activation:

Speech

• Fundamental frequency (F0) increases and becomes more variable.
• Vocal tremor amplitude increases.
• Speech rate increases under acute time-pressure stress.
• MFCC features shift as vocal tract tension increases.

Chronic vs. Acute Stress

Two distinct temporal profiles are relevant:

Acute stress - a rapid-onset response to a specific stressor (a traffic conflict, radio failure, emergency). The physiological response peaks within seconds and subsides within minutes if the stressor resolves.

Chronic stress - sustained activation of the stress response over hours or days (shift fatigue, ongoing understaffing). Chronic stress depletes cognitive resources, disrupts sleep, and impairs immune function. Its physiological signature overlaps with fatigue and is harder to distinguish from individual baseline variation.

The Brain FM targets acute stress monitoring in the first instance, using short-window predictions. Chronic stress monitoring requires longer temporal context and session-to-session comparison against individual baselines.

Labelling Instruments

UNIVERSE collects Affective Sliders and PANAS alongside NASA-TLX, enabling multi-label training for simultaneous workload and affect prediction.

Datasets with Stress Labels