Mirror Tracing Task

Background

The Mirror Tracing Task (MTT) is a classic neuropsychological test used to assess hand-eye coordination, motor learning and procedural memory. It was first published by Daniel Starch in 1910.

Typically, an MMT asks participants to trace a shape (e.g. a six pointed star) while only being able to see the shape's mirror image. The participant must trace the outline of the shape as quickly and accurately as possible, keeping their line inside a narrow boundary. Because the mirror reverses the visual field and creates a severe visual-motor conflict, the brain is forced to override its lifetime of normal hand-eye coordination.

The MMT is legendary in neuroscience due to its role in studying the famous patient H.M. (Henry Molaison). After a surgery removed H.M.'s hippocampi to treat epilepsy, he lost the ability to form any new conscious, long-term memories. In 1962, researcher Brenda Milner had H.M. perform the MMT over several days. The Result showed that H.M.'s performance improved dramatically each day, showing a perfectly normal motor learning curve. Yet, every single time he sat down to do it, he had absolutely no conscious recollection of ever seeing the star or doing the task before. These results suggest that procedural memory relies on subcortical structures (like the basal ganglia and cerebellum) rather than the hippocampus and medial temporal lobes.

MMTs typically use a special mechanical apparatus with a solid barrier blocking people's view of their own hand and the tracing paper. A mirror is positioned so that they can see only the reflection of their hand and the shape they are asked to trace. The setup of the Millisecond MMT is inspired by the computerized implementation of the task suggested by the Pittsburgh Stress Battery which uses a square and a circle as the main tracing stimuli. Millisecond added a five-pointed star as an option.

Task Procedure

The screen in the Millisecond MTT is divided into a mirror part (gray, on top) and a drawing canvas (white, on the bottom). Participants are asked to trace a shape (square, circle and 5-pointed star) on the drawing canvas (bottom) but can only see their tracing trail on the mirror image of the shape (on the top). Participants can trace the shape with the mouse (on non-touchscreen devices) or with a stylus/finger (on touchscreen devices). The visible tracing line in the 'mirror' part of the screen appears in green if the line is within the specified shape boundary. If the line goes outside the boundary, it turns red. By default, each participant works on three shapes, with 5 trials per shape. The shapes are tested in blocked design but the order of the shape blocks are randomized. Trials end if participants reach the starting circle (after leaving it) or after 45s (default).

What it Measures

The Mirror Tracing Task (MTT) is measure of hand-eye coordination, motor learning and procedural memory.

Psychological Domains

• Procedural Memory: This is the "how-to" memory system responsible for motor skills, habits, and physical tasks (like riding a bike).
• Visuomotor Coordination: The brain’s ability to synchronize visual inputs with physical hand movements.
• Cognitive Flexibility: The capacity to override highly practiced, automatic habits and adapt to new, inverted rules.
• Inhibitory Control: The mental effort required to suppress the natural urge to move your hand in the direction you see in the mirror.

Main Performance Metrics

• Success Variable: Overall proportion successfully completed trials (as well as for each shape separately)
• Tracing Duration: Overall mean tracing duration of successful trials (as well as for each shape separately)
• Track Performance: Overall mean proportion of time tracing within boundaries for successful trials (as well as for each shape separately)
• Performance Cost: Overall cost metric that relates the duration to finish tracing a shape to the time actually spent on the shape
• Pixel Errors: Overall pixel tracing errors of successful trials (as well as for each shape separately)

Psychiatric Conditions

The Mirror Tracing Task has been used with the following patient groups

• Alzheimer's Disease (AD)
• Global Amnesia (AMN)
• Huntington’s Disease (HD)
• Parkinson’s Disease (PD)

References

Search Google Scholar for peer-reviewed, published research using the Inquisit Mirror Tracing Task.

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Starch, D. (1910). A demonstration of the trial and error method of learning. Psychological Bulletin, 7, 20-23.

Carmichael, L. (1927). The History of Mirror Drawing as a Laboratory Method. The Pedagogical Seminary and Journal of Genetic Psychology, 34(1), 90–91. https://doi.org/10.1080/08856559.1927.10533064

Roig, M., & Placakis, N. (1992). Hemisphericity Style, Sex, and Performance on a Mirror-Tracing Task. Perceptual and Motor Skills, 74(3_suppl), 1143–1148. https://doi.org/10.2466/pms.1992.74.3c.1143

Richardson, A. E., & VanderKaay Tomasulo, M. M. (2011). Influence of acute stress on spatial tasks in humans. Physiology & Behavior, 103(5), 459–466. https://doi.org/10.1016/j.physbeh.2011.03.019

Julius MS, Adi-Japha E. A Developmental Perspective in Learning the Mirror-Drawing Task. Front Hum Neurosci. 2016 Mar 2;10:83. doi: 10.3389/fnhum.2016.00083. PMID: 26973498; PMCID: PMC4773595.