Staircase Experiments

Experiments

Staircase procedures automatically adjust the difficulty of trials based on a participant's performance, making them well suited for threshold estimation and signal-detection tasks. In Testable, staircase parameters are defined in the **`staircase`** column.

How staircases work

You prepare a sequence of trials in ascending difficulty order (easiest to hardest). The staircase procedure tracks correct and incorrect responses and adjusts which difficulty level to present next by moving up (harder) or down (easier) according to defined rules.

Setting up the staircase

Place the staircase parameters on the first trial of the sequence:

staircase = A: start 3, down 1, up 2, correct 2, booster 2, incorrect 1, reversal 3

On subsequent trials in the same staircase, just reference the label:

staircase = A

Parameters

Parameter	Meaning
start N	Start at difficulty level N (1-indexed, row position in staircase)
down N	Move this many steps down (easier) after a correct trial
up N	Move this many steps up (harder) after an incorrect trial
correct N	Number of consecutive correct responses required to step down
incorrect N	Number of consecutive incorrect responses required to step up
booster N	Quick step-down size used after the first correct response
reversal N	Stop after N reversals (direction changes)
trials N	Stop after N total trials regardless of reversals

Reversal vs trials termination

A reversal occurs whenever the direction of adjustment changes (from going up to going down, or vice versa). Specifying reversal 3 terminates the staircase after 3 direction changes, which produces stable threshold estimates.

Use trials N if you want a fixed number of trials regardless of performance.

Multiple staircases

You can run several independent staircases in the same experiment by giving them different labels:

staircase = A: start 3, down 1, up 2, correct 2, booster 2, incorrect 1, reversal 3
staircase = B: start 1, down 1, up 2, correct 2, booster 1, incorrect 1, reversal 4

Interleaving staircases

Group multiple staircases together by appending a :group suffix:

staircase = A:group1
staircase = B:group1

Testable interleaves the trials from grouped staircases, alternating between them throughout the session.

Results

Staircase experiments produce standard result files. The difficulty level presented on each trial is recorded alongside the response, allowing you to compute the threshold from the reversal points.

Next steps

• Trial Types: set type = test for staircase trials
• Timing Parameters: control response windows per trial
• How to Read the Results Files: analyse staircase data