Response-dependent feedback

The FB trial command allows you to classify responses according to correct key, correct number of keys, and upper and lower reaction time limits, and then define response-dependent actions.

Correct Key The response is compared with a set of keys representing the correct response key(s). The response is classified as either wrong or correct. Note that if no key is pressed the correctness is inherited from the classification regarding the correct number of keys.

Correct Number The number of registered key actions is compared with the correct number of key actions. The number is either correct or it is not.

Reaction Time The reaction time is compared with upper or lower time boundaries. The response is either too fast, normal or too slow.

The 12 possible combinations of these categories are numbered from 1 to 12 (see table below). To each of these twelve feedback classes a feedback action can be assigned that will be executed if the response falls into this category (see FB-command for examples).

If, for example, in a choice reaction task the left key should be pressed whenever a digit is presented, and the subject pressed the right key on a digit then the response is wrong and feedback class will be 1 because the key was wrong but the number of key presses was correct.

You can optionally use the MAPFB command to assign text labels to the built-in feedback classes 1..12. This will add an additional FC-column in the result file with the text labels tagging each response depending on the feedback class.

For each feedback class, a feedback action can be defined. Each line must begin with the feedback class followed by a colon.

TRIAL ShowStim
CS 2000          ; Inter trial pause of 2000 ms
RK ResKeys 1500          ; Register keys with MaxRt=1500
SP ? MidPos 1 0 1          ; Show stimulus until response or MaxRt
FB ?          ; Classify response by comparing to correct key
1:SP Wrong    Bottom 1 1000          ; Show feedback if wrong key / correct number
2:SP Correct Bottom 1 1000          ; Show feedback if correct key / correct number
3:SP Faster   Bottom 1 1000          ; Show feedback if wrong key / wrong number

Note that you do not have to define all of the twelve possible feedback actions. You may even use the FB command without any following feedback action for just including the classification in the result file only.

If you want to code responses according to the response categories of the Signal Detection Theory (SDT): Hit, Miss, False Alarm, and Correct Rejection, you must specify a dummy key name as the correct key in the signal conditions (see appendix „Feedback Classification“).

The following table provides a detailed listing of how different response types can be classified with respect to the correct key and the correct number of key presses. The table also shows what feedback classes result from this classification for correct and wrong answers by the subject.

Simple reaction (Donders A): Press SPACE anytime you see a stimulus!
Stimulus	Correct Key	Correct Number	Pressed Key	Response	FB class
any	Space	1	Space	Correct	2
any	Space	1	-	Wrong	3
Choice Reaction (Donders B): Press SHL on digits, SHR on letters!
Stimulus	Correct Key	Correct Number	Pressed Key	Response	FB class
letter	SHR	1	SHR	Correct	2
letter	SHR	1	SHL	Wrong	1
letter	SHR	1	-	Miss	3
digit	SHL	1	SHL	Correct	2
digit	SHL	1	SHR	Wrong	1
digit	SHL	1	-	Miss	3
Go/No-Go (Donders C): Press SPACE on digits, do not press on letters!
Stimulus	Correct Key	Correct Number	Pressed Key	Response	FB class
letter	Space	0	-	Correct	2
letter	Space	0	Space	Wrong	4
digit	Space	1	Space	Correct	2
digit	Space	1	-	Wrong	3
Signal detection: Press SPACE if you see a signal!
Stimulus	Correct Key	Correct Number	Pressed Key	Response	FB class
signal	SHL	1	Space	Hit	1
signal	SHL	1	-	Miss	3
no signal	Space	0	-	Corr Reject	2
no signal	Space	0	Space-	False Alarm	4

Key	Number	Normal	Rt < RtMin	Rt > RtMax
Wrong	Correct	1	5	9
Correct	Correct	2	6	10
Wrong	Wrong	3	7	11
Correct	Wrong	4	8	12