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Thom Carney, Thomas Hill, Chien-Chung Chen; W4M — A tool to simplify psychophysical research. Journal of Vision 2002;2(10):125. doi: 10.1167/2.10.125.
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The WinVis platform offers a WEB based system for designing psychophysical experiments using a database of stimulus, trial and experiment classes. To maximize flexibility the system includes tools such as W4M that rely more on end user programming skills but achieve independence from constraints of the strictly WEB based system. W4M is an extension to Matlab that integrates the WinVis system with Matlab and provides graphics system control for stimulus sequence presentation. The power and flexibility of the Matlab programming language is available for stimulus design and data analysis while W4M handles stimulus presentation and standard data analysis tasks. The integration features enable the use of stimulus objects from the WinVis database to simplify stimulus creation.
Creating an experiment using W4M generally involves five steps. First, system initialization for selecting the video mode and automatic calculation of global parameters such as pixel size in minutes. Second, define your trials, a sequence of stimuli and possibly look up table sequences. Third, select a built-in psychophysical method and modify default parameters as needed. Fourth, code the stimulus presentation and subject response loop according to the chosen psychophysical method. Fifth, provide calls to the data analysis functions and save/plot the results. Several examples of experiments designed using W4M will be presented along with a detailed description of available W4M features. The example experiments involve about 50 lines of code each.
Psychophysical research has never been easier to accomplish thanks to dramatic improvements in the graphics performance of inexpensive desktop computers, availability of software like W4M and WinVis that simplify the design and execution of experiments, and the ubiquitous WEB access for sharing of research stimulus objects and results.
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