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Pupil dilations

Apart from well-known large pupil responses (e.g., in dark adaptation) research showed that small pupil dilations (< 0.5 mm) are found in a variety of tasks, such as reaction tasks or mental arithmetic. These small dilations are considered as markers of cognitive processing in humans.

In conditioning of pupil dilations in our laboratory, the pupil diameter is measured using a head-mounted gaze tracker. Reaction tasks (Go-NoGo tasks) serve as unconditioned stimuli (US): Participants are instructed to press a button and to lift their finger ("Go") only when a tone signal is presented. On Go trials, on with the US is present, pupil dilations can be found, but not on NoGo trials, on which the US is absent. Presentation of a visual CS (conditioned stimulus) prior to the tone signal leads to anticipatory pupil dilations. In contrast, presentations of other visual stimuli on NoGo trials are not followed by pupil dilations.

For a more detailed description and application of pupil dilation conditioning see Reinhard, G., & Lachnit, H. (2002). Differential conditioning of anticipatory pupillary dilation responses in humans. Biological Psychology, 60, 51-68.