Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: January 20, 2014
Last Modified: January 06, 2023 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements the METHOD OF LIMITS to estimate 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)
2 minutes
Participants are asked repeatedly whether a red Target color is lighter or darker than a red base color. For example: the red component of the target color is lighter. As long as participants say the target red is lighter than the base red, the target red gets adjusted by a preestablished step size (editable value). Once participants reverse their answer (and say it's darker), the trial is over and the threshold is calculated as the mean between the last two red color components for the target (aka the last "lighter" and the first "darker" red component).
By default this scripts estimates the Difference Thresholds for 1 red colors (-> editable parameters), with 2 trials each, one for a lighter and one for a darker start target. The order is determined randomly for each participant (-> list.baseline_values)
1 cycle = 1 "up" sequence + 1 "down" sequence
see section Editable Instructions
File Name: limitsmethod_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 |
| cycles | Stores the number of "limit" cycles run |
| step | The stepsize with which the target color increases/decreases (default: 2) |
| parameters.initialdifference | Initial difference in the red component of target and base (default: 50+1 = 51) in this script the initial difference is selected in such a way that the adjusted targetvalues are always either above or below baseline. |
| parameters.baselineValue1 | The baseline_value of the first "limits" cycle |
| diffThreshold1 | Stores the Difference Threshold of the first cycle by design, this script only runs one cycle |
File Name: limitsmethod_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 |
| cycles | Stores the number of "limits" cycles run (one cycle runs an up and a down sequence) |
| baselineValue | Stores the color of the current base |
| targetValue | Stores the color of the current |
| direction | 1 = Down (sequence starts with targetvalue > baseline value) 2 = Up (sequence starts with targetvalue < baseline value) |
| sequenceCount | Counts how many limits sequences have been run in a cycle |
| response | The participant's response |
| latency | The response latency in ms |
| diffThresholdUp | The estimated Difference threshold for the current UP sequence (= starting with target value < baseline value) |
| diffThresholdDown | The estimated Difference threshold for the current DOWN sequence (= starting with target value > baseline value) |
| totaldiffThreshold | Mean difference threshold for one adjustment cycle (up and down) |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| responseKeyLighter: - | ||
| responseKeyDarker | The response key assignments (scancodes and labels) | |
| baselineValue1 | The baseline value (0 -> black, 255 -> brightest red) for cycle 1 to add further cycles with different basevalues add a value for each new baseline value you want to test and go to BLOCKS for further instructions. | |
| step | The stepsize with which the target color increases/decreases | 2 |
| initialdifference | Initial difference in the red component of target and base in this script the initial difference is selected in such a way that the adjusted targetvalues are always either above or below baseline. | 50+1 = 51 |
| interAdjustmentPause | Pause after an adjustment sequence in ms | 500ms |