Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: January 21, 2014
Last Modified: June 06, 2023 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements the METHOD OF CONSTANT STIMULI to estimates the difference threshold for a particular color red
Ehrenstein, W.H. & and Addie Ehrenstein, A. (1999). Psychophysical Methods. In U. Windhorst & H. Johansson, Hakan (Eds.), Modern Techniques in Neuroscience Research (pp.1211-1241). Heidelberg: Springer. (->https://uni-leipzig.de/~isp/isp/history/texts/PSYPHY-M.PDF)
3 minutes
Participants are asked repeatedly whether a red Target color is lighter or darker than a red base color. By default, 7 targetvalues (3 lighter, 3 darker, 1 the same) are presented 10 times each in a random order.
At the end a difference threshold is estimated = hypothetical targetvalue at which point participant says the red is lighter 50% of the times. => Underlying idea: Difference threshold is at the point where participant says "lighter" 50% of the times. The algorithm estimates the targetvalue at "50% lighter responses" by linear interpolation.
By default, 7 targetvalues (3 lighter, 3 darker, 1 the same) are presented 10 times each in a random
order.
At the end a difference threshold is estimated = hypothetical targetvalue at which point participant
says the red is lighter 50% of the times.
=> Underlying idea: Difference threshold is at the point where participant says "lighter" 50% of the times.
The algorithm estimates the targetvalue at "50% lighter responses" by linear interpolation.
see section Editable Instructions
File Name: constantstimulimethod_summary*.iqdat
| Name | Description |
|---|---|
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| startDate | Date the session was run |
| startTime | Time the session was run |
| subjectId | Participant ID |
| groupId | Group number |
| sessionId | Session number |
| elapsedTime | Session duration in ms |
| completed | 0 = Test was not completed 1 = Test was completed |
| parameters.step | The stepsize used to calculate the target red color values |
| baselineValue | The default baseline_value targetValue1- |
| targetValue7 | Calculates the targetvalues (here: the red color components of the target stimuli) depending on parameters.step percentupTargetValue1- |
| percentupTargetValue7 | Calculates the percentage of "lighter" responses for each targetvalue |
| noNegativeSlope | Determines whether the percentage of "lighter" response for a given targetvalue are greater or the same as the percentage of "lighter" responses for the preceding targetvalue the number of lighter reponses should NOT DEcrease for lighter targetvalues (they can, however, stay the same) !!!If expressions.NoNegativeSlope is evaluated to being false, the threshold is not determined by the script algorithm. The raw data might need to be re-evaluated manually. 0 = a negative slope was detected 1 = no negative slope was detected |
| diffThreshold | Determines the Difference Threshold (if for some reason the implemented algorithm cannot calculate a threshold, the data will read "not determined". The raw data might need to be re-evaluated manually). Implemented Algorithm Underlying idea: Difference threshold is at the point where participant says "lighter" 50% of the times. The algorithm estimates the targetvalue at "50% lighter responses" by linear interpolation. |
File Name: constantstimulimethod_raw*.iqdat
| Name | Description |
|---|---|
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockCode | Name of the current block |
| blockNum | Number of the current block |
| trialCode | Name of the current trial |
| trialNum | Number of the current trial |
| taskCount | Counts how many adjustment tasks have been run |
| baselineValue | Stores the color of the current base |
| targetValue | Stores the color of the current target Color |
| response | The participant's response |
| latency | The response latency |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| responseKeyUp:- | ||
| responseKeyDown | Response Key assignments up -> 'lighter' down -> 'darker' | |
| baselineValue | The baselinevalue (0 -> black, 255 -> brightest red) | |
| step | The stepsize used to calculate the target red color values | |
| debugDisplayTargetValue | False: debug information is not displayed on screen (default) true: debug information is displayed on screen |