Dr. Abhishek Mandal, Ph.D.

CEO, Vision Science Academy, London, United Kingdom


Vision Science Academy Exclusive


As elaborated in the first half of this article, the applicability of psychophysics principles in vision sciences is multifaceted. In addition to visual acuity and visual field testing, visual search tasks are often utilised in the psychophysical experimentation to evaluate the ability to distinguish between objects of varying colours, sizes, shapes, and orientations. Visual search refers to the ability to scan a visual scene to isolate a target object placed within a cohort of distractor stimuli. By monitoring brain activity in real time, application of psychophysical principles allows to effectively elaborate the neural networks which control the visual search mechanisms (Verghese, 2001).

Visual Search Theories

To illustrate visual search mechanisms, two distinct theories have been proposed. Firstly, the high-threshold hypothesis details that detection of a target stimulus is never altered by the presence of distractors. Therefore, if a target is actually located within the search field, visual search will identify it correctly. Otherwise, no false-positive signals will be generated. On the contrary, low-threshold hypothesis suggests that distractors can provide a false notion of target detection. Hence, in a setting with low threshold for visual errors, distractors can be identified to falsely resemble a target stimulus (Palmer et al., 2000).

Eye Tracking

An important function of visual search is to ascertain the exact point in the field of vision which is being fixated upon. Eye tracking technology is important in the monitoring of saccadic movements of the eyes which continuously occur between different points of visual fixation. By combining the principles of psychophysics and eye tracking, researchers can highlight the relationship between physical stimuli, visual perception, and cognitive processes (Martin et al., 2018).

Eye tracking is efficient in investigating a diverse range of neurocognitive and psychiatric abnormalities. Dyslexic individuals are those who encounter difficulties in reading or writing. Besides prolonging the total duration of visual fixation, it has also been noted that such disabilities can precipitate aberrant ocular saccades which in turn, can be studied by using the eye tracking technology.

The cross-link between eye tracking and psychophysics is efficient in studying the relationship between visual working memory and cognitive attention. Eye tracking can analyse the looking patterns of medical experts as they view imaging results. This role of eye tracking could be particularly useful for assessing the efficiency of medical trainees in interpreting imaging scans. Similarly, eye tracking can also analyse the fixation patterns of individuals while using digital applications. This is particularly useful for the training of professionals who are responsible for carrying out their roles under high-pressure environments such as pilots or air traffic controllers (Yang et al., 2002).


To summarise, psychophysics serves as a multidisciplinary field to explore the relationship between physical stimuli and visual sensory stimuli. Within the domain of vision sciences, psychophysics can be applied to better understand visual search mechanisms, to investigate disorders pertinent to visual acuity and visual fields, and to assess patterns of ocular motion.



Martin, J. G., Davis, C. E., Riesenhuber, M., & Thorpe, S. J. (2018). High Resolution Human Eye Tracking During Continuous       Visual Search. Front Hum Neurosci, 12, 374. https://doi.org/10.3389/fnhum.2018.00374

Palmer, J., Verghese, P., & Pavel, M. (2000). The psychophysics of visual search. Vision Research, 40(10), 1227-1268.       https://doi.org/https://doi.org/10.1016/S0042-6989(99)00244-8

Verghese, P. (2001). Visual Search and Attention: A Signal Detection Theory Approach. Neuron, 31(4), 523-535.       https://doi.org/https://doi.org/10.1016/S0896-6273(01)00392-0

Yang, G.-Z., Dempere-Marco, L., Hu, X.-P., & Rowe, A. (2002). Visual search: psychophysical models and practical
applications. Image and Vision Computing, 20(4), 291-305.

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