fixedStepStaircase objects

An object of type fixedStepStaircase is an “n-down/m-up” (i.e. n correct responses → step harder, m incorrect responses → step easier) staircase with fixed step sizes. Subject threshold is calculated as the average staircase value across reversals.

You can add columns setting properties for one or more fixedStepStaircase objects in the optional table for objects not specific to trial (experiment, device, staircase objects). [Or in the coding method: Make a fixedStepStaircase object outside trials using function fixedStepStaircaseObject, set properties, and input it to addToExperiment.]

val1

No default

Initial staircase value (a number).

stepRule

Default: step on 2 correct / 1 incorrect responses in a row

A 1×2 vector setting how many [correct incorrect] response trials in a row are needed to step the staircase value in the respective direction. e.g. <cd>[2 1]<cd> gives a 2-harder/1-easier staircase.​

stepSizes

No default

A 1×2 vector setting staircase value step sizes for [correct incorrect]. One number must be positive (increase staircase value), the other negative (decrease). Which one you make positive or negative depends on whether it’s an increasing or decreasing psychometric function.

numFastReversals
fastStepSizes

Default: numFastReversals = no fast reversals
Default: fastStepSizes = same as stepSizes above

You can set a fixed step staircase so that for the first few reversals it steps on every response and maybe takes larger steps in order to get close to the subject’s threshold fast. These “fast reversals” count toward numReversals and maxNumReversals but not threshold.

numFastReversals is number of reversals to do fast. 0 = none.

fastStepSizes is like stepSizes above.