CNP TS

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Task Description

The Color/Shape cued switching task (C/S task) is a putative measure of task-switching based on Miyake & Friedman (2004). There are other variants of two dimensional simple switching tasks (e.g. letter-number (Ref), and spatial-number(meiran)) that all are based on around a similar premise. For good reviews of task switching, see Meiran (ref), Keisel 09 (ref), Monsell (ref),

Most agree that task switching is an important component of cognitive control (monsell, friedman, sabb).

The two leading theories on the nature of the switch cost are that it is due to 'task set reconfiguration' or to 'priming'. These debates are on-going, with strong evidence on both sides, suggesting there are some situations in which each drives the switch cost effect.

There has also been substantial research on the interference (what does meiran call it again) effect gained from having competing response mappings, similar to a stroop or perhaps a flanker task.

This particular variant has been used extensively in older adolescents and adults as part of the Colorado (twin/family) studies.

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

  • Task Structure (overview of the task procedures [i.e., overall design, block, trial, and within-trial event structure and timing])
    • The C/S Task has condition by condition instructions and practice with performance criterion, followed by 192 experimental trials
      • Instructions/Practice: Screens are advanced with a right mouse click from the examiner.
        • 1. Basic task description.
        • 2. Instructions & Practice for Color (6 trials)
        • 3. Instructions & Practice for Shape (6 trials)
        • 4. Instructions & Practice for Both Together (6 Trials)
        • 5. Reiteration or repeat if participants didnt achieve 60%
      • Experimental trials (192 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
      • Instructions screens are static until advanced by examiner with a right mouse click.
      • Practice: Same as experiment
      • Experiment: Fixation cross ( ms).
      • Experiment: Cue ( ms).
      • Experiment: Cue-Stimulus Interval (200 or 1200 ms).
      • Experiment: Stimulus (500 ms).
      • The ending thank you screen is static until advanced by the examiner with right mouse click.
  • Stimulus Characteristics
    • sensory modality: Visual. Stimuli are four images: Green Triangle, Green Circle, Red Circle, Red Triangle
    • functional modality: visuoperceptual and linguistic (understanding of text).
    • presentation modality: computer display, no audio, directions are assisted by examiner.
  • Response Characteristics
    • responses required: yes
      • effector modality: Manual keyboard press.
      • functional modality: Manual keyboard press.
    • response options: left or right arrow-key press (response mapping counterbalanced across subject)
    • response collection: keyboard press and recording of responses in Eprime 2.0.

Task Schematic

Ts schema.png

Schematic with sample stimuli to the right. On every trial there is a cue that alternates between the letter and the name of the dimension to attend to (following logan & bundeson's criticism of cued-task switching 2004?).

Stimuli

Four images to the right: Green or Red colors and Circle or Triangle shape

Ts stims.png

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:

  • Fred Sabb independently checked Stone’s results in 2009 and 2010 and found his results to be accurate.
  • In July 2011, Fred Sabb cleaned the data, and created this document

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