CNP TS

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Task Description

The Color/Shape cued switching task (C/S task) is a putative measure of task-switching. The task was presented on a Dell PC running Windows XP and using E-prime (PST) for stimulus presentation. Stimuli were four colored shapes (red or green, circle or triangle). On each trial participants were cued (alternating with either a letter or word) as to which dimension is the correct task set. The cue duration was 150ms and the cue-stimulus interval (CSI) was randomized as either 200ms or 1200ms. Upon presentation of the stimulus (X ms), the participant must make a forced-choice response with the middle or index finger of their dominant hand to the left or right arrow keys (inverted-t) on an extended keyboard. The response set was bivalent (e.g. respond left for green or triangle). This was counter-balanced across subject. Thus, two of the four stimuli presented a congruent response condition (the cue was not necessary to direct the response) and an incongruent response (where the cue is necessary to determine the correct response). On one third of the trials, the cue switched from one dimension to the other. Participants performed 192 trials. The task was self-paced. Participants received three separate practice sessions to ensure encoding of the response mapping. They practiced each dimension separately for 8 trials (8 color only response trials, 8 shape trials). They then practiced both dimensions together with X switch trials. If participants performed below 60% on any block they repeated practice. If they performed below 60% on the second practice block, the task terminated.

Task Procedure

For general testing procedure, please refer to LA2K General Testing Procedure [here?].

The task was presented on a Dell PC running Windows XP and using E-prime (PST) for stimulus presentation. Stimuli were four colored shapes (red or green, circle or triangle). On each trial participants were cued (alternating with either a letter or word) as to which dimension is the correct task set. The cue duration was 150ms and the cue-stimulus interval (CSI) was randomized as either 200ms or 1200ms. Upon presentation of the stimulus (X ms), the participant must make a forced-choice response with the middle or index finger of their dominant hand to the left or right arrow keys (inverted-t) on an extended keyboard. The response set was bivalent (e.g. respond left for green or triangle). This was counter-balanced across subject. Thus, two of the four stimuli presented a congruent response condition (the cue was not necessary to direct the response) and an incongruent response (where the cue is necessary to determine the correct response). On one third of the trials, the cue switched from one dimension to the other. Participants performed 192 trials. The task was self-paced. Participants received three separate practice sessions to ensure encoding of the response mapping. They practiced each dimension separately for 8 trials (8 color only response trials, 8 shape trials). They then practiced both dimensions together with X switch trials. If participants performed below 60% on any block they repeated practice. If they performed below 60% on the second practice block, the task terminated.

Task Structure Detail

This is what we had worked on before, but could use updating. We'd like to capture a schema that can handle each of the tasks in the CNP, so please think general when editing -fws

  • Task Structure (please given an overview of the task procedures here [i.e., overall design, block, trial, and within-trial event structure and timing])
    • The BART has a series of instructional screens at the outset, followed by the experimental session comprised of 40 balloon trials.
      • Six instructional screens. Screens are advanced with a right mouse click from the examiner.
        • 1. Basic task description.
        • 2. Placement of hands and keys used for pumping and stopping (mapped based on handedness).
        • 3. Pumping description and appearance of balloon.
        • 4. Explosion description and appearance of exploded balloon.
        • 5. Reiteration of key used to stop pumping/cash in (mapped based on handedness).
        • 6. Questions screen prior to beginning task.
      • Experimental trials (40 trials). All experimental trials are preceded by a fixation cross screen.
        • Fixation cross (500 ms) screen with blank white background.
        • Balloon trial 1. Red or blue balloon presented (randomized).
          • Within-trial structure
            • Pumping increases balloon size with successively enlarged images (self-paced).
            • Participant cashes out or the balloon explodes.
            • Total points earned screen presented for 1500 ms.
        • Balloon trial 2 begins after a fixation cross screen, and this is sequence is repeated for 40 trials.
      • End. Thank you screen presented. Grand Total Points also displayed.
    • Timing
      • Instruction screens are static until advanced by examiner with a right mouse click.
      • Fixation cross screens (500 ms).
      • Balloon images are static until participant presses the pump key. Pressing the pump key instantaneously presents the following balloon image (either a slightly larger balloon or an exploded balloon).
      • Images of an exploded balloon are presented for 1500 ms, with Total Points text underneath.
      • When the participant cashes out, just the Total Points text is presented for 1500 ms.
      • The ending thank you screen is static until advanced by the examiner with right mouse click.
  • Stimulus Characteristics
    • sensory modality: Visual. Balloons are either red or blue. Balloon images start with a size of 154 X 154 pixels and are increased in height and width by 2 pixels with each pump. The fixation cross is black text in size 18 bold font in Comic Sans MS.
    • functional modality: visuoperceptual and linguistic (understanding of text).
    • presentation modality: computer display, no audio, directions are assisted by examiner.
  • Response Characteristics
    • responses required: left or right key press for pumping or cashing in. Button mapping is based on handedness.
      • effector modality: Manual button press.
      • functional modality: Manual button press.
    • response options (e.g., yes/no, go/no-go, forced choice, multiple choice [specify n of options], free response): yes/no, pump or cashout.
    • response collection (e.g., examiner notes, keyboard, keypad, mouse, voice key, button press): Button press and recording of responses in Eprime 2.0.

Task Schematic

Schematic of the Balloon Analogue Risk Task

Task Parameters Table

TaskParamTable.png

Stimuli

Stimuli consist of red or blue balloons which begin with a size of 154 X 154 pixels and are increased in height and width by 2 pixels with each pump. When a balloon explodes, an image comparable in size and color is displayed as a burst balloon for 1500 ms.

A white screen with a black fixation cross (size 18 bold font in Comic Sans MS) is presented for 500 ms before every balloon trial.

Dependent Variables

There are four conditional variables in this C/S task:

  1. Cue-stimulus interval, long or short task preparation interval of 1200 or 200 ms;
  2. Congruency, whether the two dimensions of the stimulus created conflict in response;
  3. Switch condition, whether the previous trial was of the same dimension as the current trial (color or shape);
  4. Response choice, whether the response choice was the left or right button.

We used these variables to identify several task indicators of behavioral performance. As commonly seen in the literature, we defined switch cost as the difference in reaction time (RT) between repeat trials and switch trials at the short CSI. Residual switch cost was the same RT difference at the long CSI. We defined interference as the difference in reaction time between congruent and incongruent response sets. We also defined response switch as the difference in RT between repeated button presses and switching from one button to the other.


Cleaning Rules

We trimmed the data to include correct only trials with a 3SD trim on the mean and removing switch trials where there was an error at n-1.


Code/Algorithms

History of Checking Scoring:

  • Andy Dean independently checked Stone’s results in 2009 and 2010 and found his results to be accurate.
  • In April 2011, A

Data Distributions

  • Performance on key behavioral indicators used in cued-switching paradigms that was consistent with the literature.
  • Average reaction time of 813 ms and overall accuracy of 96.5% across all conditions.
  • Subjects had an average switch cost of 216ms for the short cue-stimulus interval (CSI) when using correct only trials for analysis.
  • They also had a residual switch cost (at long CSI) of 64.5 ms again using only correct trials.
  • They showed significant interference with ambiguous stimuli (requiring the cue to determine the direction of response) at both short (46ms) and long (35ms) CSIs.


References