Requires : information about the screen width in cm and pixels and the viewing distance in cm This is, of course, dependent on the distance that the participant sits from the screen as well as the screen itself, so make sure that this is controlled, and remember to change the setting in Monitor Center if the viewing distance changes. Use degrees of visual angle to set the size and location of the stimulus. For running an experiment it’s usually best to use something like ‘cm’ or ‘deg’ so that the stimulus is a fixed size irrespective of the monitor/window.įor all units, the centre of the screen is represented by coordinates (0,0), negative values mean down/left, positive values mean up/right.įor help understanding spatial units visually, try the builder demo “spatialUnits” under “Understanding PsychoPy” (version 2021.2). For conducting demos, the two normalised units (‘norm’ and ‘height’) are often handy because the stimulus scales naturally with the window size. Your choice of unit depends on the circumstances. In PsychoPy ®, after providing information about your monitor, via the Monitor Center, you can simply specify your stimulus in the unit of your choice and allow PsychoPy ® to calculate the appropriate pixel size for you. In most other systems you provide the stimuli at a fixed size and location in pixels, or percentage of the screen, and then have to calculate how many cm or degrees of visual angle that was.
PLACE SHAPES IN LOCATIONS ON SCREEN USING PSYCHOPY SOFTWARE
One of the key advantages of PsychoPy ® over many other experiment-building software packages is that stimuli can be described in a wide variety of real-world, device-independent units.
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