Symbol Counter Task
Background
The Symbol Counting Task (SCT) is a cognitive test used to measure executive control, specifically the mental processes of updating working memory and shifting attention. Hugh Garavan and colleagues published the paradigm in 2000 to isolate the specific brain regions involved in cognitive switching and working memory updates using fMRI technology. The tasks consists of presenting participants with sequences of varying lengths that consist of two different symbols (e.g. a large and a small square). Participants are asked to mentally track the counts for the two symbol separately for a later test. Garavan et al. identified a shared network, including the bilateral parietal and left dorsolateral prefrontal cortex, responsible for executive functions like switching attention and updating working memory.
Task Procedure
Participants work on 18 sequences of small and big squares and have to keep a separate count for each of the two square types. Afterwards, participants are asked to select the count for each square type out of 20 possible options and receive feedback.
The 18 different sequences run three different switch intensities (low, medium, high) and each switch intensity runs 6 different sequence lengths (11, 12, 13, 14, 15, 16). A low frequency switch trial always runs only one switch. A medium switch sequence runs about 1/4 switches, and a high frequency switch sequence runs about 1/2 switches. The switch positions are always randomly selected.
Each trial sequence presents the squares for 1500ms each, preceded by a fixation cross for 100ms. Once all squares have been presented, participants are asked to select the counts for the two symbols from two drop boxes. They get 12 seconds to select the counts before they receive feedback for 1000ms. A rest trial separates each trial sequence from the next.
Participants work through one practice sequence before the test.
What it Measures
The Symbol Counting Task (SCT) is a measure of executive control, specifically the mental processes of updating working memory and shifting attention.
Psychological domains
- Executive Control: Collection of "top-down" mental processes used to manage and regulate thoughts and actions
- Working Memory: Storing and updating the last item of each target category
- Sustained Attention: Maintaining focus over a repetitive series of trials without 'drifting
Main Performance Metrics
- Accuracy: Proportion Correct Answers on both counts by switch intensity
- Mean Errors: Mean absolute deviations from the correct counts by switch intensity
Psychiatric Conditions
The SCT has been used with the following patient groups:
- Attention Deficit Hyperactivity Disorder (ADHD)
- Schizophrenia
- Major Depressive Disorder (MDD)
- Traumatic Brain Injury (TBI)
- Multiple Sclerosis (MS)
The Symbol Counter Task as described in Garavan (1998).
References
Search Google Scholar for peer-reviewed, published research using the Inquisit Symbol Counter Task.
Garavan, H. (January 01, 1998). Serial attention within working memory. Memory & Cognition, 26, 2, 263-76.
Garavan, H., Ross, T. J., Li, S. J., & Stein, E. A. (January 01, 2000). A parametric manipulation of central executive functioning. Cerebral Cortex (new York, N.y. : 1991), 10, 6, 585-92.