A circular checkerboard (dartboard) pattern. Properties set options for size, pattern, scaling of radial check sizes (e.g. for cortical scaling), amplitude/contrast, and color, as well as an option for flicker. You can also show solid concentric rings if you set number of angular checks = 1.

For dartboard retinotopy using isolated wedges or rings, see element type dartboardRetinotopy. For fixation see element types dots, cross, fixationGrid, etc.

▸ Object ends on its own?

"Ends on its own" means ends automatically at that point. If an element can end on its own, you don't need to set end conditions for it in property end (unless you want it to maybe end earlier).

No—runs until any condition you set in property end.

Input properties

Adjustable properties

You can vary or allow the subject to adjust the following properties of an object of this type when it's running. If you need to make other properties adjustable, you can edit the element type code—see Element Type Programming Manual.

Adjustable properties

Adjustable properties





Default: diameter = 10 deg
Default: centerDiameter = 0.2 deg

diameter is diameter of the checkerboard (deg).

centerDiameter is diameter of the center area, which is transparent (deg).


Default: numAngularChecks = 20
Default: numRadialChecks = 8

numAngularChecks is integer number of segments (light or dark) around the dartboard at any radius.

numRadialChecks is integer number of segments in any radial line, from edge of the transparent center area to outer edge of the dartboard.

e.g. numAngularChecks = 4, numRadialChecks = 1 → a dartboard consisting of four segments in quadrants.


Default: equal radial check sizes

You can use this property to apply cortical (or other) scaling factors to check sizes in the radial direction. A row vector of numbers > 0 that are scale factors for radial sizes, from innermost to outermost. Number of factors must = numRadialChecks above. The absolute magnitudes of the factors don't matter, only relative magnitudes. Final radial sizes are automatically scaled to fit numRadialChecks into the radius from edge of the transparent center area to outer edge of the dartboard.


<cd>[]<cd> = equal radial check sizes.


Default: immediate check in quadrant 1 = light

0/1 setting the initial pattern: 0 = check innermost, right, and below display center = dark, 1 = light. Note currently the dartboard is always centered at element position, with a boundary between checks along the right horizontal bisector. Element position can be set in property position.


Defaults: mean intensity = 0.5, amplitude = 0.5 → black & maximum intensity

These properties work together to set the two intensities in the checkerboard.

meanIntensity is a number between 0–1 (black-maximum) setting the mean intensity of light and dark segments.

Also set one of:

amplitude is max intensity − mean intensity.


contrast is Michelson contrast, amplitude / mean intensity. If you set contrast, meanIntensity must be > 0.

It's possible to set a combination of these properties that causes the grating to clip at intensity 0 or 1. See record properties maxAmplitude and maxContrast below.


Default: white

A 1×3 RGB vector with numbers between 0–1. This defines color at intensity = 1. Color at intensity = 0 is <cd>[0 0 0]<cd> (black).


Default: no flicker

Frequency of switching between dark–light (cycles/sec). 0 = no flicker.

Input properties all visual elements have


Input properties all adjuster elements have


Input properties all objects have


Record properties

PsychBench uses record properties to record information during experiments. You can't set record properties but you can see them in experiment results using input property report.


Values for input properties amplitude and contrast that would cause intensity to clip at 0 or 1 given the current value of meanIntensity.