Psychosensory Pupil Response
Objective: This is a review article describing pupillometry methodology and the psychosensory pupil response (PPR) - measurement of pupil dilation in response to increased arousal, mental effort, and cognitive activity
Gather these items before starting the experiment. Check off items as you prepare.
Software1
Not specified
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Protocol Steps
Stimulus presentation setup
Present full-screen colored light (blue or red) on a computer monitor to the subject
Note: Both blue and red light conditions should be tested
View evidence from paper
“10 s of blue or red light presented on a computer monitor, followed by 20 s of a dark screen”
Dark period presentation
Present a dark screen following the light stimulus to measure pupil dilation recovery
Note: Dark period allows measurement of pupil recovery to baseline size
View evidence from paper
“10 s of blue or red light presented on a computer monitor, followed by 20 s of a dark screen”
Measure latency period
Record pupil response latency from stimulus onset - the period during which the pupil does not yet respond to light
Note: Latency depends on stimulus intensity and age of subject
View evidence from paper
“[Light on] 0–0.2s: This is the latency period during which the pupil does not yet respond”
Measure rapid constriction phase
Record the strong and rapid pupil constriction phase until minimum pupil size is reached
Note: This phase represents the initial constriction response driven by rods and cones
View evidence from paper
“[Light on] 0.2–1.5s: The pupil constricts strongly and rapidly until it reaches its minimum size”
Measure sustained constriction or pupil escape phase
Record whether pupil remains fully constricted or shows unconstriction (pupil escape) while light remains on
Note: Blue light leads to sustained constriction; red light leads to pupil escape due to different photoreceptor sensitivity
View evidence from paper
“[Light on] 1.5–10s: The pupil either remains fully constricted while the light remains on, or unconstricts (redilates) slightly”
Measure recovery phase
Record gradual pupil dilation and recovery to original baseline size following light offset
Note: Recovery is slower than constriction; recovery is faster for red than blue light. After high-intensity blue light, pupil may remain slightly constricted for many minutes (post-illumination pupil response)
View evidence from paper
“[Light off] 10 s–30s: The pupil gradually recovers to its original size. Dilation due to light offset occurs much more slowly than constriction due to light onset”
Express pupil size as proportion of baseline
Calculate and express all pupil size measurements as a proportion of pre-stimulus pupil size
Note: This normalization allows comparison across subjects and trials
View evidence from paper
“The y axis indicates pupil size as a proportion of pre-stimulus pupil size”
Repeat trials
Conduct multiple trials for each light color condition
Note: Example protocol used N=10 trials per color
View evidence from paper
“N = 10 trials per color”