Dictionary for RITMO Course on Pupillometry

Definitions of some of the core terminology used in the course on pupillometry. Please let us know if something is missing.

Arousal: A physiological and psychological state of being activated, excited, and attentive. It is controlled by the autonomic nervous system, in particular the sympathetic branch, and when arousal increases, it leads to increased heart rate and blood pressure, skin conductance response, pupil dilation, and readiness to respond. Arousal is important in regulating consciousness, attention, alertness, and information processing.
Artifact: Unwanted uncontrolled effect during an experiment. In pupillometry, artifacts are often erroneous data points that can result from technological problems (e.g., the eye-tracker failed to record correctly, data processing steps like interpolation or filters skewed the data) or physiological responses (e.g., blinks, falling asleep, the eyes moving out of frame).
Baseline: A physiological measurement in rest condition, without stimulation, so that it can be used as a control comparison of the effectiveness of a stimulus or when being engaged in a task.
Cognition: Mental processes such as attention, perception, imagery, memory, language, thinking.
Constriction of the pupil: A decrease in pupil diameter from baseline.
Demographic data: Information about a person such as age, gender, cultural background, etc. Such information is often collected in experiments to have background information about participants.
Descriptive analysis: The analysis of a phenomenon in terms of its statistical feature, for example, the kinematics of the pupil (changes over time like velocity or acceleration) or spatial features (size of the pupil). Descriptive analysis may often be a useful “objective” starting point for further inferential analysis (whether a condition differs significantly from another condition).
Dilation of the pupil: An increase in pupil diameter from baseline.
Ecological setting: In research experiments, there is often a trade-off between controllability (being in control of all variables) and ecological validity where something is studied in its natural context. For example, studying a musician in a lab (controllable) or on stage during a concert (ecologically valid).
Embodied cognition: In the field of embodied cognition, cognitive processes are explained as being inseparable from the body. The perceiver is not only a passive receiver of information that is being processed and understood in the brain alone. Rather, the perceiver interacts with the environment. See also Internet Encyclopedia of Philosophy entry.
Eye tracking: The method of measuring the position of the eyes' gaze (where one is looking) and its movements (saccades). Nowadays is most common to measure eye fixations and movements with a computerized eye-tracker device that is sensitive to infrared light. Because eye trackers identify the iris and eye pupil in order to monitor eye position and movements, most commercial eye trackers also provide the size of the pupil, either in millimeters of diameter or arbitrary units (e.g., camera pixels).
Interpolation: Interpolation is a method of creating new data points within the range of known data points. The methods is often used in pupillometry to 'fill-in' data samples that were lost or blank because of eye blinks or various temporary technical problems with the eye tracker.
Locus Coeruleus: A nucleus in the pons of the brainstem and part of the reticular activating system. The locus coeruleus is the principal site for the synthesis of norepinephrine (noradrenaline) in the brain.
Mental Effort: The amount of cognitive work required by a given task. Each cognitive task imposes relative demand by a particular task, in terms of mental resources required. Also called cognitive workload.
Modality: The term modality can be understood as a channel of sensory information. It includes, but is broader than, the five senses seeing, hearing, tactility, taste, and smell.
Motion capture: A technique for measuring and storing human body motion through various types of technological systems.
Oddball paradigm: In psychology, in an "oddball" detection task, participants respond to target stimuli that occur infrequently and irregularly within a series of standard stimuli (e.g., C notes are played every second but an A note is interspersed occasionally within the series of notes). The oddball paradigm was first used in event-related potential (ERP) but it has been extended to other methods. The oddball paradigm has robust effects on pupil dilation and it depends on activity of the subcortical Locus Coeruleus.
Participant: A person taking part in an experiment.
Perception: To sense and experience, identify or discriminate something (e.g., a sound, a color, a specific object or scene).
Predictive Coding: A theory that postulates that the brain is constantly generating and updating predictions about the environment. According to the theory, an internal mental model is used to predict sensory signals that are then compared with the actual input signals from those senses to identify 'prediction errors' that can lead to adjustments of the model or improved perceptual sampling. The current theory originates with Helmholtz's (1860) concept of unconscious inference.
Pupillometry: The method of measuring the size of of the eyes' pupils. Nowadays is most common to obtain quantitative measurements of the pupils' diameters with computerized eye-tracker devices that are sensitive to infrared light. These can typically measure pupil sizes while the eye is stationary (fixations) or moving (saccades).
Qualitative analysis: Analysis based on verbal or categorical information and using interpretation and reasoning as methods. Qualitative analysis is often used in the humanities and parts of the social sciences.
Quantitative analysis: Analysis based on numerical data using mathematical and statistical methods. Quantitative analysis is often used in the natural sciences but increasingly also in other fields.
Sampling frequency: The sampling frequency is the number of times per second a phenomenon is measured and stored as a number. For eye tracking, sampling frequencies can vary between 30 and 1000 Hz (30 to 1000 measurements per second). However, with pupillometry little is gained by sampling at frequencies higher than 100 Hz and 60 Hz is appropriate for most purposes.
Stimulus: A term used in psychology to describe what the subjects perceive (e.g., see a picture or video; listen to a musical piece) in an experiment.
Time-varying descriptors: Descriptors that are calculated from short, sequential time-frames and then forming a sequence of numbers.
Waveform: A waveform representation of a signal shows how its amplitude varies over time.

Published Oct. 7, 2025 3:53 PM - Last modified Oct. 7, 2025 4:00 PM