Random Screen Positions

Commands:

FP Fill Positions

LP Load Position

MP Mix Position

RP Reset Position

KP Keep Position

This set of commands supports random processes to display random pictures on random screen locations of a Position definition.

For example, if you define a Position representing a circle, you can use the FP command to load a target picture and fill the remaining positions of the circle with random distractors. Using the LP trial command you can load more than one picture. For each Position definition, the loaded pictures and screen locations are memorized for the remainder of the running trial. Use the KP trial command to keep the load status across trials.

Once a picture has been memorized, it will not be drawn from any set to fill empty screen locations of the same Position. Once a screen location is used, it will not be filled with random pictures. Use the RP trial command to reset a Position definition. This will clear any loaded pictures and screen locations. You can also use it to remove the most recent loaded picture.

The MP-command mixes the position indices within a position definition. Unlike the FP- and LP-command, the mixed position indices have permanent lifetime across trials.

The integrated random mechanisms are very powerful and direct because they lead to an immediate loading of the picture. The disadvantage is, however, that they cannot be stored in a variable and thus have only a limited lifetime, and that they are limited to visual presentations. Use the generic random commands if you want to define more complex random processes or if you want to randomly select data objects other than pictures (see Generic Random Processes).