What is the difference between explicit and implicit memory?

Explicit or declarative memory encompasses factual information like birthdates or what you ate for lunch. Implicit or procedural memory includes knowledge you cannot easily put into words, such as how to skate or navigate home without knowing street names. Motor memories fall within implicit memory and require motor learning to develop.

How does the mirror drawing paradigm measure motor skill acquisition?

Mirror drawing measures motor learning by having participants trace a star shape while viewing only the mirror reflection. Researchers count the number of times participants cross the borderlines in each session, then graph errors against session number. Improvement over time and faster learning after breaks indicate motor skill acquisition and retention.

What equipment is needed to set up a mirror drawing experiment?

A mirror drawing experiment requires a pencil, a mirror approximately 12 inches by 8 inches that stands independently, and an occluder made of wood, foam, or cardboard. Position the mirror about 12 inches from the table edge and the occluder about 6 inches from the edge to block direct viewing. The stimulus is a large star with a smaller star inside for participants to trace.

What does the savings effect reveal about motor learning?

The savings effect occurs when participants make fewer errors in the session following a long break compared to their first session of the day. This demonstrates retention of previously learned motor skills. Combined with steeper improvement slopes after breaks, the savings effect provides evidence that motor learning has occurred and persists over time.

How does sleep influence motor skill learning and retention?

Research using mirror drawing shows that participants who napped between sessions made fewer errors than those without sleep breaks. This indicates sleep promotes retention of recently learned motor skills and increases the rate of improvement. Sleep appears to consolidate motor memories, allowing faster learning on subsequent testing days.

What did the H.M. case study reveal about memory systems?

Patient H.M. had his hippocampus removed to prevent seizures, resulting in severe anterograde amnesia preventing new explicit memories. However, H.M. performed normally on mirror drawing tasks, showing retention and rapid improvement. This famous case demonstrated a distinction between explicit and implicit memory systems, supported by different brain regions.

Why does motor skill learning transition from difficult to automatic?

Motor skill acquisition involves implicit or procedural memory, which develops through practice and becomes automatic over time. Initially, learning new skills like driving requires conscious effort and explicit attention. Eventually, the skill becomes second nature through repeated practice, allowing faster performance with less conscious deliberation.

Motor Learning in Mirror Drawing

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1. Stimuli design

This experiment requires a mirror that can stand on a table on its own, 2 ft by 2 ft (though larger is fine), as well as a flat rigid surface at least as big as an 8.5 x 11 in piece of paper, that can stand on its own while slightly tilted. A piece of wood with a stand or a piece of foam core is good. We will call this the occluder. The experiment also requires a pencil.
Place the mirror about 12 in from the edge of a table, standing upright. Place the occluder so that it is about 6 in from the edge of the table, occluding the view of the space between the table and the screen.
Print out several pieces of white paper with a large star on it and a slightly smaller star within the bigger one (see Figure 1).

Figure 1: Star stimulus for use in mirror drawing. The participant’s task will be to trace the star, trying to stay within the boundary of the two outlines.
Place the paper with the star on it between the occluder and the mirror.

2. Running the experiment

Instruct the participants to place the pencil tip down at any point on the star, between the two borderlines. Without lifting the pencil up, they should trace around the star, coming fully back around while trying to stay within the borders. Count the number of times they cross a border as errors.
After each session, give the participant a break for at least 10 min.
Label each piece of paper with the session number (e.g., Day 1, Session 1).

3. Analysis

Record the number of times the participant crossed the borderlines in each experimental session. Generally, the number of errors will decline over time, reflecting motor learning.

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!