Table 2

Paradigms used for studying anxiety (as contrasted here for utility with fear)

Threat of shockThreat-of-shock paradigms instruct participants who may be in one of two conditions: ‘safe from shock’ (during which no shocks are received) or ‘at risk of shock’ (during which shocks may be received). Shocks may occur during the ‘at-risk’ blocks but with a low probability and generally are scheduled independently of task performance. Other tasks may be performed with blocks of these contexts to investigate the effects of this sustained threat on other cognitive processes. This is often measured using the eyeblink reflex, in a procedure known as ‘startle’. Greater anxiety is thought to correspond to the augmentation of the eyeblink reflex.
Low dose (7.5%) of CO2 Inhaling air with >7.5% CO2 concentration over a period of around 20 minutes increases both subjective experience of and physiological symptoms associated with anxiety.
DarknessAs humans are a diurnal species, this task elicits anxiety and potentiates anxious responses (eg, startle) by contrasting lighted conditions with complete darkness.
Vigilant threat monitoringParticipants observe a line fluctuating on the screen which they are told reflects their own physiological levels of ‘anxiety’ (though in fact this line is generated by experimenters), and when this line passes a threshold they will receive a shock. They are instructed to remain calm and avoid accumulating shocks.
Context conditioningDuring normal conditioning procedures, conditioning occurs either to the stimulus (cued conditioning) and/or to the context (context conditioning). The context here refers to features of the environment that are present during the conditioning procedure. Context conditioning is separate to the typical ‘cued conditioning’ used in fear learning paradigms due to the decreased temporal precision of the association between the context and the unconditioned stimulus.
Long-duration CSThis paradigm is similar to typical fear conditioning, in that a predictive stimulus (CS) is paired with an unconditioned aversive stimulus (US), except that the duration of presentation of the CS is longer, typically upwards of 30 seconds.
Approach-avoidance conflictThis type of paradigm, a translation of the animal paradigm of operant conflict, involves a choice or conflict between approaching rewards and avoiding punishments, and has been argued to be anxiogenic.
  • These paradigms often include aversive stimuli such as shocks, but may also be used with other aversive stimuli such as aversive noises/pictures or blasts of cold air. The commonality among all these paradigms is that they all evoke a sustained anxiety state.

  • CS, conditioned stimuli.