Weber’s law is one of the most studied phenomenons in experimental psychology. Weber’s law gets used to study the response of human beings to stimuli in a quantitative manner. The law gets used to describe human sensation and perception (Goldstein, 2010). Weber’s law states that the just noticeable difference- JND, is a constant proportion of the original stimulus.
This research proposes to measure the just noticeable difference thresholds of the participants using a psychophysical experimental procedure to prove Weber’s law (Rajamanickam, 2002). This research will aim to replicate Weber’s phenomenon using an adaptive psychophysical procedure in an attempt to fulfill the requirements for psychology research methods course.
Weber was a 19th century experimental psychologist who observed that the size of the difference threshold sufficed to be lawfully related to initial stimulus magnitude. This relationship forms the basis for Weber’s Law, which gets simply expressed as; ∆I/I =k (Rajamanickam, 2001). ∆I represents the difference threshold while I stands for the initial stimulus intensity. K represents the constant signifying the equation gives a constant despite variations of the I term. Weber’s Law can get told straight forwardly as; the size of the just noticeable difference- ∆I is a constant of the original stimulus value (Rajamanickam, 2002).
Weber’s Law gets applied to a variety of sensory modalities such as brightness, mass, loudness, and line length. The constant of Weber’s fraction varies across these different modalities, but it is mostly constant within a specific task modality (Rajamanickam, 2002). This study aims to investigate Weber’s phenomena and replicate it in an experiment as a requirement for psychology research methods class. This study will apply a psychophysical method based on threshold psychophysics to replicate Weber’s law for line lengths.
Adaptive procedures in psychophysical research
Research on sensation and perception has become extra sophisticated over the last century. As a result, new adaptive methodologies have arisen as a way to improve on reliability and efficiency of measurement (Leek, 2001). An experimental procedure gets referred to as adaptive if the physical features of the stimuli on each trial get evaluated by the stimuli and responses from previous trials or sequence trials.
This research will measure the just noticeable difference thresholds for participants using a psychophysical procedure known as the adaptive method (Goldstein, 2010). In this method, the participants’ responses to each trial after systematic manipulation of the stimulus level in line with the experimental dimension of interest gets collected (Walter & Addie, 1999). A series of stimulus responses initiated during the course of the experiment and the associated participant responses will result from this method. The objective of the experiment is to get to measure the characteristics of the participant’s performance over a short duration without negating on quality of the results (Leek, 2001).
Adaptive staircase method
The adaptive staircase method gets adopted in many laboratories as a procedure of choice due to its simplicity and flexibility (Leek, 2001). This method uses the previous or more responses within an adaptive track to select the next trial placement, and provide a threshold estimate in various ways (Leek, 2001). This method mostly averages the turnaround points during the adaptive track. There is a reduction in stimulus if the participant’s response is positive and an increase in stimulus level if the response is negative. Starting at a level above threshold, positive responses result to continued decrease in stimulus levels till the point a negative response occurs (Goldstein, 2010).
Goldstein, E. B. (2010). Sensation and Perception. New York: Cengage Learning.
Leek, M. R. (2001). Adaptive Procedures in Psychophysical procedures. Perception and
Rajamanickam, M. (2002). Modern Psychophysical And Scaling Methods And Experimentation.
New Delhi: Concept Publishing Company.
Walter H Ehrenstein, A. E. (1999). Psychophysical Methods. 1-31.