Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: January 11, 2014
Last Modified: January 14, 2023 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements a Flicker Paradigm to investigate the role of attention in Change Blindness based on:
Rensink, R.A., O'Regan, J.K. & Clark, J.J. (1997). TO SEE OR NOT TO SEE: The Need for Attention to Perceive Changes in Scenes. Psychological Science, 8, 368-373.
NOTES: • This script runs with 6 example stimuli (ONLY intended for demonstration purposes). The original study ran with 48. • the variable "interest level of change" (central vs. marginal) is not included in this script as the example stimuli contain "marginal interest" changes only. • this script runs 2 cue conditions (cue vs. no cue) either in a mixed design (default) or in a blocked design. The script does not include an unreliable cue condition as tested by Rensink et al.
Millisecond thanks Dr. Rensink for sharing his example stimuli for this script!
6 minutes
Participants are presented "flickering" presentations of original and altered pictures for a maximum cycle of 1 min (default). The task is to find the one difference between the two pictures. If participants find the difference they are instructed to press the Responsekey (original: Spacebar) and are asked to describe the change in detail in a textbox.
3 (change types: location, color, presence/absence) x 2 (cue conditions: no cue, cue); tested within
Change types are tested by default in a mixed design. To run them in a blocked design: change parameters.runcuecondition (editable parameter).
If the conditions are run in a blocked design, the order of the cue conditions is determined randomly in this script.
Cues in this script alert participants to the type of change: color, location or the addition/removal of an object
(a) Blocks:
1. Practice: by default, the script runs as many practice trials as specified under parameters.max_numberoftrials_practice (default: 1)
and selects the stimuli randomly from item.practice_stimA.
Rensink et al ran 6 (=3 changetypes x 2 interest levels; interest levels are not tested in this script by default)
2. Flicker_MixedCue: by default, the script runs 6 trials
3. Flicker_Cue/Flicker_NoCue: by default, the script runs 3 trials per block (stimuli are randomly assigned to either one of them)
(b) Trial Sequences:
1. cue-field screen: 3000ms
-> the cue condition is selected at random
2. blank screen: 1000ms
3. Cycle: the selection of the individual pictures is random
original (240ms) -> flicker (80ms) -> original (240ms)-> flicker (80ms) -> altered (240ms) -> flicker (80ms) -> altered (240ms) -> repeat of cycle if noResponse
(maximum cycle duration: ~1 min)
all durations are editable parameter. They can be changed under EDITABLE CODE -> Editable Values
4. Change Description: if a change was reported (by pressing Responsekey):
a) a forced-choice question with 3 answer choices asks participants to select the type of change observed
b) a textbox asks participants to describe the observed change in detail
The provided stimuli are example stimuli generously shared by Dr. Rensink under
https://www2.psych.ubc.ca/rensink/flicker/download/index.html
They are only intended for demonstration purposes.
Substitute your own stimuli under EDITABLE CODE -> Editable Stimuli and follow instructions
The instructions used in this script are not original. They are provided by Millisecond in html-format.
To change the instructions, simply change the html files in a simple Text Editor
(e.g. in 'Notepad' in Win or 'textEdit' in Mac)
File Name: FlickerParadigm_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 |
| runCueCondition | By default, the cuecondition (cue vs. no cue) is run in a "mixed" design; to run the cuecondition in a blocked design, set value.runcuecondition = "blocked" |
| countPracticeRuns | Counts how often the practice round was repeated |
| countALL | Counts all test trials run |
| countNRAll | Counts all no responses |
| countResponses | Counts how often participants clicked the mouse/touched the screen to report the change |
| countL | Number of LOCATION trials run |
| countNRL | Number of no responses in LOCATION trials |
| propCorrectChangeTypeSelectionsL | Proportion correct selection of Change Type in LOCATION trials (based on responses made) |
| rtCorrSelectionsL | The mean latency (in ms) of cycles when participant selected the correct change in LOCATION trials |
| countP | Number of PRESENCE trials run |
| countNRP | Number of no responses in PRESENCE trials |
| propCorrectChangeTypeSelectionsP | Proportion correct selection of Change Type in PRESENCE trials (based on responses made) |
| rtCorrSelectionsP | The mean latency (in ms) of cycles when participant selected the correct change in PRESENCE trials |
| countC | Number of COLOR trials run |
| countNRC | Number of no responses in COLOR trials |
| propCorrectChangeTypeSelectionsC | Proportion correct selection of Change Type in COLOR trials (based on responses made) |
| rtCorrSelectionsC | The mean latency (in ms) of cycles when participant selected the correct change in COCATION trials |
File Name: FlickerParadigm_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, group, | With the current subject/groupnumber |
| 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 |
| flickerSame | The duration of the blank screen/flicker in between the 2 presentations of the original pictures (or altered pictures) (original: 80ms) if set to 0 the presentation of the pictures appears continuous |
| changeType | "location" (1), "presence/absence" (2), "color" changes (3) in the pictures |
| cueCondition | 1 = a cue is given; 2 = no cue is given |
| cue | The currently presented cue |
| countTrials | Counts the number of trials |
| countCycles | Counts the number of cycles started until a response occurs |
| currentpic | The itemnumber of the currently presented (original/altered) pic |
| stimulus | The image presented (StimA) |
| responsePoint | Determines the image in the response cycle (the cycle that participant made a positive response) that was presented when participant made response "StimA1", "flicker_AA", "StimA2", "flicker_AB", "StimB1", "flicker_BB", "StimB2", "flicker_BA" or "N/A" (if no response was given) |
| alternations | Determines the number of alternations between original and altered pictures until response occurs each switch between originals and altered pictures as well as each switch between altered pictures and original pictures is counted as an alternation. => for each completed cycle, participant go through 2 alternations if the response occurs AFTER the change from original to altered pic in the last cycle, one more alternation is added to the count. |
| cycleRt | Stores the combined trial latencies across the entire cycle until response occurs (in ms) |
| selectedChangeType | The selected observed change type ('location', 'presence/absence', 'color', or empty) |
| accChangeType | 1 = the correct Change Type was selected 0 = in any other case |
| currentChange | Contains the correct description of the change |
| changeDescription | Stores the openended textbox response in regard to the observed change |
| accChangeDescription | "needs to be evaluated" script does NOT evaluate the correctness of the entered response automatically. Each openended response needs to be evaluated manually. |
| changeReportRT | Stores the time it took participant to work on the openended response until pressing the button (in ms) |
| repeatPractice | 0 = the practice round should not be repeated 1 = the practice round should be repeated |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| responseKey | The response key | " " -> spacebar |
| cueBoxHeight | Height of the cuebox in percentage of canvas height (original: 10%) | |
| cueBoxWidth | Width of the cuebox in percentage of canvas width (original: 30%) | |
| cueTextHeight | The height of the cue text in percentage of canvas height (original: 5%) | |
| picHeight | The height of the pictures in percentage of canvas height (original: 70%) | |
| cueDuration | The duration of the cue in ms (original: 3000ms) | |
| startScreenDuration | The duration of the start screen in ms (original: 1000ms) | |
| stimADuration | The duration of the original picture in ms (original: 240ms) the original picture is presented twice. If parameters.flicker_same = 0 the presentation of the 2 original pictures appears continuous | |
| stimBDuration | The duration of the altered picture in ms (original: 240ms) the altered picture is presented twice. If parameters.flicker_same = 0 the presentation of the 2 altered pictures appears continuous | |
| flickerSame | The duration of the blank screen/flicker in between the 2 presentations of the original pictures in ms (or altered pictures) (original: 80ms) if set to 0 the presentation of the pictures appears continuous | |
| flickerDifferent | The duration of the blank screen/the flicker in between original and altered pictures in ms (original: 80ms) | |
| maxCycleDuration | The ~maximum duration of the cycling through original and altered pictures if no response occurs in ms (defaul: 60000ms) | |
| maxNumberofTrials | The number of test stimuli . NOTES a) In the mixed design all stimuli are presented within one block. In the blocked design, half the stimuli are presented in the cue, the other half in the nocue block (random sampling). b) The original study (Rensink et al used 48 stimuli)-> change images under EDITABLE CODE -> Editable Stimuli | 6 |
| maxNumberofTrialsPractice | The number of practice stimuli tested | 1 |
| runCueCondition | By default, the cuecondition (cue vs. no cue) is run in a "mixed" design; to run the cuecondition in a blocked design, set value.runcuecondition = "blocked" | |
| allowPracticeRepeats | 1 (true): the practice round can be repeated if so indicated (default) 0 (false): the practice round cannot be repeated |