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Motor Activity

Motor activity is movement. The ability to create a well coordinated movement is a form of intelligence, requiring many of the same processes as visual scene recog­nition and language comprehension.

Coordinated movements of an athlete or dancer require sophisticated activity within the nervous system. The same problems (and solutions) that arose when considering visual scene analysis and language comprehension rise again when considering motor coordination.

Motor activity requires split second integration of many sources of infor­mation, like vision. It is endlessly crea­tive, expressing a unique final product adapted to complex requirements, like language.

Like other forms of cognition, motor activity is based on schemata: forms or patterns learned through experience. Like the other forms of cognition, motor activity is influenced by a complex mix of conscious and unconscious processing.

Early research on motor activity

Historians of psychology trace the begin­ning of research on motor activity to the astronomer Friedrich Wilhelm Bessell around 1820. Bessell was trying to figure out why different astronomers could not agree on the location of a particular star in the sky at a particular moment. In doing so, he stumbled on the concept of reaction time.

What were the "personal equations" studied by Bessell?

Each astronomer was supposed to write down the exact time of a star's alignment with crosshairs in a telescope. Bessell discovered there were consistent individual differences in how quickly the astronomers recorded the time.

Some individuals delayed a fraction of a second more than others. Bessell constructed "personal equations" to correct for differences in how quickly the astro­nomers could make their obser­vations. He had discovered differences in average reaction times of observers.

Forty years later, Wilhelm Wundt made reaction time one of the most frequently used measures in the first experimental psychology laboratory. Reaction time (the time that elapses between a stimulus event and a reaction) are still very common measurement in modern psychology.

Reaction times can be measured precisely. They are easily manipulated with statistics (because time is on a ratio scale with a true zero).

In today's laboratories, reaction time measures are among the simplest forms of measurement with computer programs. They show, for example, the effects of priming in semantic networks, as discussed in Chapter 6.

Motor skills research entered the realm of business and industry in the 1920s with the time-motion studies of Taylor. These studies were intended to improve efficiency of industrial and office workers.

What were time-motion studies?

After analyzing the precise sequence of movements required for a particular job, researchers could modify a task. They redesigned working environments to make jobs faster.

For example, a time-motion expert might relocate the bins that contained parts alongside an assembly line. Small changes might shave a few seconds off the time needed to complete a task.

What sort of work did World War II stimulate?

World War II brought a new era of research into motor coordination. Soldiers often had to operate compli­cated machinery under stressful conditions. This led to a focus on variables like practice, fatigue, and stress and how they influenced motor performance.

Flying a plane presented another unique set of demands. Early cockpits were not well organized. A pilot had to monitor numerous dials while manipulating complex hand controls. This led to fatal errors.

The focus on how humans interacted with machines helped create a new discipline called human factors. It studied the relationship of people to complex technologies such as machines and other tools, including whole working environments. We will review it in the context of industrial-organizational psychology in Chapter 15.

Measuring Hand/Eye Coordination

Scientists in the middle of the 20th Century developed several well-known pieces of laboratory equipment to study motor performance. Of particular interest was hand-eye coordination, the ability of humans to make complex hand move­ments adjusted to a continually changing visual input.

Hand-eye coordination is required in many skilled tasks. Individual differences in this ability affect the performance of people in work and recreational settings such as assembly jobs and sports.

One widely used tool for studying hand-eye coordination was the pursuit rotor apparatus, shown in the following illustration.

picture of pursuit rotor apparatus
A pursuit rotor apparatus

A pursuit rotor consists of a turntable-like platter with a metal spot on it. The subject holds a wand with a metal tip. The subject tries to keep the tip on the metal spot (activating a timer) as the platter turns.

What is the pursuit rotor task?

To keep the wand on the metal spot, the subject must track the circular movement of the turntable. The speed of rotation can be varied. A person with better coordination will keep the tip of the wand on the metal spot a longer time.

A second tool commonly used to study motor control is the mirror-tracing apparatus. A subject is given a design, such as a star, to trace with a pencil. The subject views his or her hand in a mirror. A barrier blocks direct sight of the hand.

The mirror reverses and disrupts normal visual-motor coordination. Initially, the hand (seen in the mirror) moves in ways opposite to what the subject expects.

mirror tracing apparatus
A mirror tracing apparatus

What is mirror tracing?

People gradually learn to reverse the normal hand-eye relationship. With practice they become increasingly adept at mirror tracing.

Standardized tasks like these provide a way to study motor learning. Mirror-tracing was used with the famous patient H.M.

By testing H.M. on the mirror-tracing apparatus, neuropsychologists showed he could learn procedures. This sug­gested procedural memory was distinct from event memory.

H.M. formed no new event memories. He never remembering practicing on the mirror-tracing apparatus, although his abilities with it improved.

The Learning Curve

With repetition of almost any motor task, learning occurs. A person becomes more efficient or effective at carrying out a task.

In the pursuit rotor tasks, time spent on the metal dot increases. In the mirror-tracing task, the tracing becomes more accurate.

Progress in skill learning commonly follows an S-shaped curve, with some measure of skill on the Y-axis and number of trials on the X-axis. Progress is slow at first, then a subject may experience a burst of learning that produces a rapid rise on the graph.

learning curve
The S-shaped learning curve typical of complex learning

What is the shape of the usual learning curve?

People sometimes refer to plateaus or periods of no improvement during skill learning. However, when experimenters looked for such a phenomenon, they did not find it.

Fitts and Posner (1967) found gradual improvement with practice in almost all motor skills. They said flatly there were "no plateaus." Fred Keller of Harvard referred to the "phantom plateau" since one seldom occurred, but people believed that it did.

What did Fitts and Posner say about "plateaus" in motor learning?

What people call a plateau may be a period of stability after a skill is learned as well as it can be learned. Most growth processes follow the same S-shaped curve as motor learning.

In general, an S-shaped curve of growth levels off because stability is attained, a resource needed for growth is limited, or a ceiling of performance is reached. For example, mirror tracing cannot improve forever.

Given enough time to practice any skill, one should become very good at it, then improvement stops. This is a plateau of sorts, indicating maximum competence has been attained.

What causes the "S-curve" pattern?

The S-shaped learning curve is most obvious when someone learns a highly complex task. The initial part of the curve rises slowly as a person becomes familiar with basic components of a skill.

The steep ascending phase occurs when there is enough experience with rudi­ments or simple components to start putting it all together. Rapid progress follows until the skill hits a ceiling or stabilizes at a high level.

How do people mis-use the term "steep learning curve"?

People often speak of a steep learning curve when they mean the opposite. A steep learning curve would be produced if a skill improved quickly. That would indicate something easy to learn.

However, what most people mean by "steep learning curve" is difficult learning experience. No doubt they are thinking of steep hills and steep mountains that make climbing difficult. In actuality, the steepest part of the learning curve is the part where learning is fastest.


Fitts, P. M. & Posner, M. I. (1967) Human Performance. Belmont, CA: Brooks/Cole.

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