DmDX help, Glossary

DMDX Help.

Glossary.

In DMDX there are specific terms that refer to unique DMDX things, I'll attempt to enumerate them here.

Clock On. The command to start gathering an RT in DMDX is referred to as a "clock on".
Correct Response indicator. Indicates which response within an item is the correct one.

CR indicator. Short for correct response indicator (above).

Item. An item is one display sequence that normally gathers one reaction from a subject. Items occur following the parameters in an item file. The only unique thing differentiating one item from the next is the semi-colon at an item's end. Semi-colons are only usable as item delimiters, they can never be displayed or used for anything else. An item usually consists of a correct response indicator, an item number and a series of frames, if not it's just one frame.
Item File. An item file is a file that contains the script DMDX is going to follow and it is a Rich Text File (so it has a .RTF file extension). It consists of two things, parameters and items.
Item number. Items have numbers both to identify the response in the output file and also to indicate the item type (instructions that don't gather RTs for instance have an item number of zero).
Frame. A frame in an item is one display element. Normally frames are presented in a timewise sequence however they can be presented simultaneously. A frame can contain switches and an optional text segment. Frames are delimited by forward slashes (/)
Parameter. In the first section of an item file parameters are listed. In old item files the parameters were limited to the first line of the item file, nowadays an extended parameter line is possible. Parameters are active for the entire run.
Refresh Interval. The time between one refresh of the screen and the next, also referred to as a tick (see below).
RT. Reaction Time, usually the time the subject takes to respond to a stimulus.

Run. When DMDX is told to execute a script we refer to it as running an item file.
Switches. Switches are options that occur in items (as opposed to the parameter line) and are normally only active for the frame the switch occurs in as distinct from parameters that are active for the whole item file -- however there are switches that are also parameters depending on whether they are used in a frame or the parameter line. Sometimes a switch will refer to the old DM/DMTG single character options as opposed to the DMDX keyword options that are angle bracket delimited words with optional arguments.
Text segment. A text segment occurs between double quotes in a frame of an item. There can only be one text segment in a frame (more double quotes can occur in a keyword's arguments however). A text segment can also be used as a file name if certain switches are present in an item.
Tic. Alternative spelling of Tick (below). Sometimes I use tic and other times I use tick, sorry.
Tick. A tick is a retrace interval (the time between one vertical retrace and the next) or the time to refresh the display once. On a 60 Hz display this is 1/60th of a second or 16.666 milliseconds and most displays are 60 Hz ones. If you don't know what your display's refresh rate is you can use TimeDX's Refresh Rate test. Times of displays in DMDX are usually specified in ticks because in the past all displays had to be some integer number of ticks (largely to keep monitors from blowing up and so forth), prior to the freesync video mode modifier there was no way to present a display for a fraction of a tick.

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