Studying motor learning allows for the investigation of, and better understanding into, distinct cognitive mechanisms. For instance, the process of acquiring a new motor skill, such as driving, at first seems arduous but eventually transitions to become second nature.
Experimental psychologists divide up learning and memory processes into subtypes that are associated with different brain systems.
These subtypes distinguish between the knowledge for facts and knowing how to do something. Explicit or declarative memory encompasses factual information, like a birthdate, or what one ate for lunch. Implicit or procedural memory includes things a person cannot quite put into words, like how to get home despite not knowing the street names, or how to skate.
Within the domain of implicit memory lays motor memories. Such memories require motor learning to occur.Learning to walk on a balance beam is a good example.
Using the commonly employed mirror drawing paradigm, this video demonstrates how to setup and perform a study to investigate the acquisition of motor skills, as well as how to analyze and interpret the data.
A mirror drawing experiment requires a pencil, a mirror with dimensions of about 12 inches by 8 inches and that can stand on its own, and an occlude made of wood, foam, or cardboard that can also stand independently. The occluder blocks the direct viewing of the table, requiring the participant to use the mirror to see.
Position the mirror about 12 inches from the edge of a table, standing upright. Next, place the occluder about 6 inches from the edge of the table, making sure that the view of the space in front of the mirror is blocked.
A key component of this experiment is the stimulus, which is a large star shape with a smaller one within it. No matter what the shape is, the stimulus will always consist of a path for the participant to trace.
As the last step before the participant arrives, label the paper with the session number, and place it in the space on the table between the occluder and the mirror.
During each testing session, sit the participant at the table in front of the occluder. Inform him or her that he or she will be tested in multiple sessions with rest breaks in between.
Now instruct the participant to place the pencil tip down at any point on the star, between the two borderlines. Without lifting the pencil up, have him or her trace around the star, coming fully back around, and trying to stay within the borders.
After each session, give the participant a break for at least 10 min.
The analysis for mirror drawing involves counting the number of times the participant crossed the borderlines in each experimental session.
The counted errors are then graphed by plotting the number of errors in a session as a function of session number.
For this participant, overall performance or accuracy in tracing improved over time. Two lines of evidence suggest motor learning occurred.
First, in the session following the long 2-hour break, the participant made fewer errors than in the first session of the day. This savings effect suggests retention of what was learned before the break.
Second, the rate of improvement-the slope of the curve-was steeper after the 2-hour break. Such slopes suggest that the participant learned more quickly, given that learning had previously taken place.
Now that you are familiar with setting up a mirror drawing experiment, let's look at how experimental psychologists use the technique to investigate mechanisms that involve motor learning.
For example, researchers use mirror drawing to investigate the impact of sleep on motor learning. One experiment compared a group of participants that took a nap between sessions against another group that did not sleep during the breaks between sessions.
A decrease in the number of errors for the napping group indicated that sleep promotes retention of recently learned motor skills, as well as a greater rate of improvement.
Perhaps the most famous application of mirror drawing involves the case of patient Henry Gustav Molaison (H.M.) who had most of his hippocampus, a brain region important for the formation of new memories, removed in order to prevent life-threatening seizures.
Fortunately, the surgery worked and his seizure's subsided. Unfortunately, H.M. suffered severe anterograde amnesia making him unable to form new explicit memories.
Amazingly, when it came to mirror drawing, H.M. performed just like everyone else-he showed retained improvements and more rapid improvements on subsequent testing days. This famous study led to the recognition of a distinction between explicit and implicit memory and the brain systems supporting them.
You've just watched JoVE's introduction to mirror drawing. Now you should have a good understanding of how to setup and perform an experiment, as well as analyze and assess the results.
Thanks for watching!