stimulusFrames attribute

Member of

Syntax

/ stimulusFrames = [framenumber = stimulusname, stimulusname, ...; framenumber = stimulusname, ...]

or

/ stimulusFrames = [framenumber = listname]

or

/ stimulusFrames = [framenumber = selectMode(stimulusname, stimulusname, stimulusname, ...)]

Parameters

Name

Type

Description

framenumber

integer

A non-negative integer specifying a vertical retrace frame.

selectmode

selectmodeenum

Value	Description
constant	Constant selection of a single item.
current	Currently selected item of a stimulus or counter.
next	Next selected item of a stimulus or counter.
noReplace	Random selection without replacement.
noReplaceCorrect	Random selection without replacement if response is correct.
noReplaceError	Random selection without replacement if response is incorrect.
noReplaceNoRepeat	Random selection without replacement or repeating an item.
noReplaceNot	Random selection without replacement excluding the current item.
not	Synonym of noreplacenot.
random	Synonym of noreplace.
replace	Random selection with replacement.
replaceNoRepeat	Random selection with replacement and without repeating an item.
replaceNot	Random selection with replacement excluding the current item.
sequence	Sequential selection in the listed order.
serial	Synonym of sequence.

stimulusname

stimulus

The name of a stimulus defined elsewhere in the script to be presented on the specified frame.

listname

list

The name of a list that selects the stimulus to be presented on the specified frame.

Remarks

The stimulusFrames attribute schedules stimuli to be presented on particular vertical retrace frames in the <trial>’s frame sequence. The framenumber represents the ordinal position of the frame within the sequence. If a stimulus is assigned to a frame, it will be displayed at the onset of that frame. If no stimulus is assigned to a frame, the display is not changed during that frame and previously displayed stimuli will remain visible. Multiple stimuli can be assigned to a single frame, in which case all of those stimuli are displayed simultaneously at the onset of the frame.

Alternatively, stimulus presentation can be defined in terms of milliseconds using stimulusTimes.

A vertical retrace frame is the interval during which a the screen is painted from top to bottom. Video presentation on a digital monitor is not continuous over time but instead consists of discreet frames during which the screen is painted (think of the frames in an animated cartoon or a motion picture). On a digital monitor, stimuli must therefore be presented for durations that are multiples of a duration of a single frame, and the shortest time interval a stimulus can be presented is the duration of 1 frame.

On most standard monitors, the screen is repainted every 16.7 ms (60 hz) or 13.9 ms (72 hz) — these frequencies are known as the vertical frame rate or simply the frame rate. Some video systems permit the frame rate to be adjusted in the Windows control panel. Consult your hardware dealer to determine how to adjust the frame rate for your monitor.

Examples

The following trial presents a forward and backward masked prime for exactly 1 vertical retrace frame, and then presents a target stimulus that remains on the screen until the subject responds:

<trial myTrial>
/ stimulusFrames=[1=forwardmask; 2=prime; 3=backwardmask; 4=target]
/ validResponse=("a", "b")
/ correctResponse=("a")
</trial>

The following trial presents a forward and backward masked prime for exactly 1 vertical retrace frame, and then presents a target stimulus that remains on the screen until the subject responds. The particular forward and backward mask used on each trial are selected from list elements called forwardmaskselector and backwardmaskselector respectively:

<trial myTrial>
/ stimulusFrames=[1=list.forwardmaskselector; 2=prime; 3=list.backwardmaskselector; 4=target]
/ validResponse=("a", "b")
/ correctResponse=("a")
</trial>

The following trial presents a focusstimulus for 10 vertical retrace frames, then presents a two stimuli simultaneously on the left and right of the screen:

<trial myTrial>
/ stimulusFrames=[1=focusstimulus; 10=lefttarget,righttarget]
/ validResponse=("a", "b")
/ correctResponse=("a")
</trial>