Letter Memory Task
Background
The Letter Memory Task is a classic cognitive-behavioral measure of executive functioning and specifically addresses the 'updating' subcomponent of executive control that involves monitoring and coding incoming information for relevance and replacing old, no-longer-relevant information with newer data. Specifically, the Letter Memory Task requires participants to monitor and continuously update a series of letters to keep track of the last three letters of the sequence.
The task, adapted from an earlier design by Neil Morris and Dylan M. Jones in 1990, was used by Akira Miyake and colleagues in the early 2000s to study the relationship of several executive functions (set shifting, updating, inhibition). They could show that these functions were highly correlated with each other due to a common, heritable factor ('unity') but also differed due to genetic influences unique to each function ('diversity'). Friedman et al (2008) further showed that the correlation between these three executive functions can be explained by a highly heritable common factor that goes beyond general intelligence or perceptual speed but that each function was further impacted by unique, genetic influences.
Task Procedure
Participants view series of letters (N = 5, 7, 9), one at a time in the middle of the computer screen. Each letter is randomly selected and is presented for 2.5 seconds. Whenever a new letter comes on screen, participants must rehearse out loud the last 3 letters in the series. After the last letter disappears, participants select the last 3 letters from a provided letter matrix; while the instructions ask to keep the actual order of the letters intact, accuracy measures don't depend on it. Participants receive performance feedback after each trial.
After a short practice phase of three trials (one for each level of N), the test phase runs 12 trials (4 repeats of the three levels of N). The set size order is randomly determined with the constraint that every set size appears once every 3 trials.
What it Measures
The Letter Memory Task is a cognitive-behavioral test of executive control, particularly memory updating abilities
Psychological domains
- Executive Control: Collection of "top-down" mental processes used to manage and regulate thoughts and actions
- Working Memory: Storing and updating the list of target letters
- Sustained Attention: Maintaining focus over a repetitive series of trials without 'drifting'
Main Performance Metrics
- Accuracy: Proportion correct test trials (proportion of trials where all 3 letters were correctly recalled -in any order)
Psychiatric Conditions
Because the Letter Memory Task requires high cognitive load, continuous monitoring, and quick deletion of old information, it is highly sensitive to the frontal lobe and striatal dysfunctions present in many clinical conditions. The primary patient and clinical groups evaluated with this task include:
- Schizophrenia
- Obsessive Compulsive Disorder (OCD)
- Traumatic Brain Injury (TBI)
- Mild Cognitive Impairment (MCI) & Dementia
- Insomnia
The Letter Memory Task as described in Miyake & Friedman (2012) in which participants are presented a series of letters as they try to remember the last three.
References
Search Google Scholar for peer-reviewed, published research using the Inquisit Letter Memory Task.
Morris, N., & Jones, D. (1990). Memory updating in working memory: The role of the central executive. British Journal of Psychology, 81, 111.
Inman, Tina Hanlon, Vickery, Chad D., Berry, David T. R., Lamb, David G., Edwards, Christopher L., & Smith, Gregory T. (1998). Development and Initial Validation of a New Procedure for Evaluating Adequacy of Effort Given During Neuropsychological Testing: The Letter Memory Test. Psychological Assessment, 10(2), 128-39.
Greub, B., & Suhr, J. (2006). The validity of the letter memory test as a measure of memory malingering: Robustness to coaching. Archives of Clinical Neuropsychology, 21(4), 249-254.
Friedman, N., Miyake, A., Young, S., DeFries, J., Corley, R., Hewitt, J., & Ferreira, Fernanda. (2008). Individual Differences in Executive Functions Are Almost Entirely Genetic in Origin. Journal of Experimental Psychology: General, 137(2), 201-225.
Miyake, A., & Friedman, N. (2012). The Nature and Organization of Individual Differences in Executive Functions. Current Directions in Psychological Science, 21(1), 8-14.