Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Credits:
Millisecond thanks Dr. Stark for sharing the new site with us!
Created: January 28, 2014
Last Modified: June 17, 2026 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements the Mnemonic Similarity Task (MST), previously known as the 'Behavioral Pattern Separation Task', by Start et al (2013). The MST provides a sensitive measure for memory changes across the life span and is useful for the early detection of memory impairments.
Stark, S.M, Yassa, M.A., Lacy, J.W. & Stark, C.E.L. (2013). A task to assess behavioral patternseparation (BPS) in humans: Data from healthy aging and mild cognitive impairment. Neuropsychologia, 51, 2442–2449.
12 minutes
Participants participate in a 2-part experiment to assess recognition memory. The first part of the experiment presents 128 pictures (default) of everyday items and participants have to decide whether the item is an OUTDOOR or an INDOOR item. The second part of the experiment presents 64 of the previously seen pictures (targets), 64 of very similar items (lures), and 64 new items (foils). Participants are asked to categorize the items as old, new, or similar within 2.5s (default).
There are two sets of stimuli: set C and set D. This script runs set C by default (editable parameter)
The sets are downloaded via https://darwin.bio.uci.edu/~cestark/BPSO/bpso.html (inactivated)
(now: https://faculty.sites.uci.edu/starklab/mnemonic-similarity-task-mst/)
Each set comes with a/b variants of each items:
The 'a' variants are used for part1 and for targets and foils in part2. (-> item.Stimuli/item.stimuli)
The 'b' variants are used for lures in part2. (-> item.Stimuli_lures/item.stimuli_lures)
The stimuli for each set are stored in separate subfolders.
If you only need a specific subfolder, it's not necessary to upload the second folder as well.
Instructions are adapted from the originals downloaded via https://darwin.bio.uci.edu/~cestark/BPSO/bpso.html (inactivated)
(now: https://faculty.sites.uci.edu/starklab/mnemonic-similarity-task-mst/)
They can be customized in script mst_instructions_inc.iqjs
File Name: mst_X_summary*.iqdat
| Name | Description |
|---|---|
| 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 |
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| completed | 0 = Test was not completed 1 = Test was completed |
| showResponseKeyReminder | True (1) = a text reminder is presented onscreen (while pictures are presented) that reminds participants of response keys false (0) = no response key reminder is presented (default) |
| stimSet | "C","D","E","F" (whichever set was selected) |
| setSize | Number of trials per trial type condition in part 2 (default: 64) |
| nrSubsetImages | Number of items per trial type condition as well as subset number (default: "64") Choose from "64", "20-1", "20-2", "20-3" => sets are separated into 3 test sets for repeated measures "32-1", "32-2" => sets are separated into 2 test sets for repeated measures if something other than these options is chosen, the script defaults to "64" |
| selfpaced | True = the task is self-paced => the pictures are still presented for the pre-determined duration but participants have as much time as needed to complete the respective tasks before the next stimulus shows up false = task is not self-paced (default) |
| stimulusDuration | Stimulus presentation time (default: 2000ms) |
| isi | Interstimulus interval (default: 500ms) |
| countl1-countl5 | Helper variables that keep track of how many lures of each of the 5 categories have been sorted into list.lures |
| minLureFreq | The minimum number of lures of each lure bin |
Absolute Response Counts For Targets, Lures, And Foils (Explained Only For Targets) |
|
| countOldTargets | Counts all "old" responses to targets |
| countSimTargets | Counts all "similar" responses to targets |
| countNewTargets | Counts all "new" responses to targets |
| countTargets | Counts all target trials |
| countTargetsCorr | Counts all target trials that were responded to => all target trials minus those with no responses |
Relative Response Counts For Targets, Lures, And Foils (Explained Only For Targets) |
|
| rawRateOldTargets | Proportion of "old" responses to all target trials (includes no responses) |
| rawRateSimTargets | Proportion of "similar" responses to all target trials (includes no responses) |
| rawRateNewTargets | Proportion of "new" responses to all target trials (includes no responses) |
Response Accuracy For Targets, Lures, And Foils (Explained Only For Targets) |
|
| corrRateOldTargets | Adjusted proportion of "old" responses to target trials that were responded to (no responses excluded) |
| corrRateSimTargets | Adjusted proportion of "similar" responses to target trials that were responded to (no responses excluded) |
| corrRateNewTargets | Adjusted proportion of "new" responses to target trials that were responded to (no responses excluded) |
Lure Bins Summary Statistics |
|
| l1 - l5 | Counts how often lures of category 1-5 were run (raw count) |
| l1NR - l5NR | Counts 'no reponses' (NR) to all 5 bin lure categories |
| L1O - l5O | Counts how often lures of category 1-5 were categorized as "old" (raw count) |
| l1S - l5S | Counts how often lures of category 1-5 were categorized as "similar" (raw count) |
| l1N - l5N | Counts how often lures of category 1-5 were categorized as "new" (raw count) |
| rawPercentCorrect | Overall percent correct rate (takes all responses into account; includes no responses) |
| corrPercentCorrect | Adjusted overall percent correct rate (takes only those trials with a response into account; no responses are excluded) |
| ldi | Lure Discrimination Index (LDI): rates corrected for no responses (Main MST Measure) => "hit" rate for lures (=proportion of similar responses to lure objects) - "false alarm" rate for foils (=proportion of similar responses to foil objects) |
| tri | Traditional Recognition Index (TRI): rates corrected for no responses => hit rate for targets (=proportion of old responses to old objects) - false alarm rate for foils (=proportion of old responses to foil objects) |
File Name: mst_x_raw*.iqdat
| Name | Description |
|---|---|
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| stimSet | "C","D","E","F" (whichever set was selected) |
| setSize | Number items per targets/foils/lures |
| nrSubsetImages | Number of items per trial type condition as well as subset (default: "64") Choose from "64" => no subsets possible "20-1", "20-2", "20-3" => sets are separated into 3 test sets for repeated measures "32-1", "32-2" => sets are separated into 2 test sets for repeated measures if something other than these options is chosen, the script defaults to "64" |
| blockcode | The name the current block (built-in Inquisit variable) |
| blocknum | The number of the current block (built-in Inquisit variable) |
| trialcode | The name of the currently recorded trial (built-in Inquisit variable) |
| trialnum | The number of the currently recorded trial (built-in Inquisit variable) trialnum is a built-in Inquisit variable; it counts all trials run even those that do not store data to the data file. |
| stimulus | Stores the currently presented picture |
| stimulusSelect | The itemnumber of the currently presented picture |
| trialType | The current trial type 1 = target 2 = foil 3 = lure |
| lureBin | The lure bin of current lure (1-5); 0 for targets and foils The more mnemonically similar lures in lure bin1 (L1) and ranks mnemonical similarity to one of the targets L1: highest mnemonical similarity -> L5: lowest mnemonical similarity |
| response | The scancode of the response key part1: 23 = I (indoor); 24 = O (outdoor) part2; 47 = V (old); 49 = N (new); 48 = B (similar) |
| responseCategory | The 'interpreted response' part1; "indoor" vs. "outdoor" part2: "old", "new", "similar" |
| correct | The correctness of the response (1 = correct; 0 = incorrect) only relevant for Part 2 (accuracy of responses in Part 1 is not assessed in this script) |
| latency | The response latency in ms; measured from onset of stimulus |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
Design |
||
| showResponseKeyReminder | True = a text reminder is presented onscreen (while pictures are presented) that reminds participants of response keys false = no response key reminder is presented | false |
| nrSubsetImages | Number of items per trial type condition as well as set number Choose from "64" => no subsets possible "20-1", "20-2", "20-3" => sets are separated into 3 test sets for repeated measures "32-1", "32-2" => sets are separated into 2 test sets for repeated measures if something other than these options is chosen, the script defaults to "64" | "64" |
| selfpaced | True = the task is self-paced => the pictures are still presented for the pre-determined duration but participants have as much time as needed to complete the respective tasks before the next stimulus shows up false = task is not self-paced | false |
Timing Parameters |
||
| stimulusDuration | Stimulus presentation time | 2000 |
| isi | Interstimulus interval the combined duration of stimulusduration and ISI = response window | 500 |