PDM - Progressive demasking software
PDM is a program designed for running progressive demasking experiments on Windows 2000/XP based computers. The program is written by and for researchers in cognitive psychology and is covered by the GNU public license.
In a progressive demasking trial a target-mask pair is presented consecutively several times until a response is made by the participant. During the trial, the total display duration of the target and mask pair is held constant, but the ratio of the target display duration and mask display duration is increased progressively. At the beginning of a trial (in the first cycle), the mask display duration is greater than the target display duration. As the cycle increases, the mask duration is decreased and the target duration is increased by the same amount of time. This makes the target progressively appear from the mask. The following table shows the display duration (in milliseconds) for consecutive cycles in a trial for the target-mask pair [TABLE ; #####].
|Cycle||TABLE duration||##### duration||Total duration|
|14||until response||0||until response|
Please, see sections v.3.4, v.3.3, addons based on v.3.4, addons based on v.3.3.
A program mode (test mode) is added where the response registration at the end of the trial is omitted, and where the masks and stimuli alternate between a black and a white background to make them visually separable for the optocoupler. There are no other differences between the test mode and normal operation. This mode is available to every user (using a parameter in the ini file), so everybody can easily do a noninteractive run to test his experimental computer.Other changes are noted in the comments of the source files.
- Addon 1 (zip archive)
Specific PDM for studies with children (no pause ; each trial is launched with a RETURN key hit ; option for random trials ; outputfile fits daily studies with mutiple experimenters and computers).
- Addon 2 (zip archive)
Specific PDM with images (image filenames are read from the ’stim.txt’ file, BMP images are read in the ’user_input’ directory, BMP are displayed instead of words and masks). Please note that ’image PDM’ settings (found in the ’pdm.ini’ file) do not change from regular sotware settings. All the parameters are needed but some are not active, such as font definition for masks. Please, pay attention to the image size you want to display. Big image (several MB) are not fully displayed in one refresh cycle. Please, note that the screen size parameter in the ’ini’ file must correspond to the image size for a full display.
A simple version of a Lexical Decision Task (LDT)
- Addon 2 (zip archive)
Specific PDM with confidence value on each participant’s response
Stéphane DUFAU, Michael STEVENS & Jonathan GRAINGER
(1,3 - CNRS & Aix-Marseille University, Marseille, France ; 2 - Ghent University, Ghent, Belgium)
You can reward the PDM developers for their effort by referring to the Behavior Research Methods article that describes PDM. Here’s the reference :
Dufau, S., Stevens, M. & Grainger J. (2008). Windows executable software for the progressive demasking task (PDM). Behavior Research Methods, 40(1), 33-37 (pdf)
The PDM functions are covered by the Gnu public license. The PDM documentation is covered by the Gnu free documentation license. This means that PDM is free, open source and guaranteed to remain free.