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Measurement of Perceptual Effects of Afterimages
Afterimages are defined as “optical illusions, particularly well perceived when fixating an image for an extended period of time and then looking at a neutral background, where an inverted copy of the original stimulus appears” (Ritschel & Eisemann, 2012, p. 529). The mechanism of afterimage perception is complex and not entirely understood. However, it is considered that afterimages are mainly defined by retinal kinetics (Spillmann & Werner, 2012). The purpose of the project is to explore further into the mechanisms of human brightness perceptions in the situation of changing luminance.
Aims and Research Questions
The research aims to detect electrophysiological correlates of afterimages in humans and to report possible oscillatory responses of the visual system. The findings will allow the researchers to substantiate the explanation of mechanisms leading to visual after-effects in brightness perception. The project will aim to answer the following questions:
- How does the degree of image contrast affect the recovery from a bleach?
- How does the time of exposure affect the recovery from a bleach?
- How can oscillatory responses be modified by a contrasting phenomenon against dark and bright backgrounds?
To achieve a greater level of findings’ generalisation, a simple randomised sampling technique will be used. The estimated total number of participants is 100-150. The quantitative design methodology will be used, and the experiment will be administered in two phases. Initially, participants will be exposed to vertical grading images with gradually decreasing contrast. On the second stage, they will be exposed to higher-contrast images during a longer period (10-15 seconds). The results of the two experiments will be compared. The data about oscillatory responses, as well as stationary patterns, will be recorded via electroencephalography (EEG). The subjective perceptions, as well as demographic data, will be collected by using questionnaires.
The linear regression will be administered to control confounding variables, i.e. age, gender, etc., to reduce possible biases associated with them. The given tool allows examining the links between distinct covariates (demographic and multicultural indicators) and a numeric outcome (perceptional and retinal response to a breach). The statistical analysis of the results obtained in the two experiments will be carried out with independent measures t-test. The given tool allows identifying if the means of two groups are statistically different from each other.
In any research that implies the involvement of respondents, it is important to take into account participants’ confidentiality. The term confidentiality implies “the process of protecting an individual’s privacy” or, in other words, non-violation of a person’s control over “the extent, timing, and circumstances of sharing oneself (physically, behaviorally, or intellectually) with others” (“Privacy and confidentiality,” n.d., para. 1-2). In some cases, by disclosing private information of study participants, the researcher may harm their social identity and cause damage to their psychological well-being. Thus, adherence to this ethical standard is essential.
The project costs will include the fees for the purchase of the SPSS software. The investment in the given statistical tool is important as it will allow carrying out all the necessary analytical procedures and tests aimed to measure different variables and find answers to the formulated research questions. Additionally, some expenditures will be associated with learning and rent of necessary equipment, e.g., EEG. Overall, it is expected that the total costs will account for about £1500, excluding educational fees.
Privacy and confidentiality. (n.d.). Web.
Ritschel, T., & Eisemann, E. (2012). A computational model of afterimages. Computer Graphics Forum, 31(2), 529-534.
Spillmann, L., & Werner, J. S. (2012). Visual perception: The neurophysiological foundations. San Diego, CA: Academic Press.