Chapter 5Memory

Human Performance Engineering

Robert W. Bailey, Ph.D.

Third Edition

Designers should be aware of three

types of human memory:

sensory, short-term, long-term

1. Sensory – Persistence of a stimulus

For vision- Duration of sensory memory can be lengthened by optimizing the stimulus-

background contrast.

Difficulties with visual sensory memory

would show up as errors characterized

by a lack of pattern or an excess of visual confusion.

DLTRVSA

More errors in the rightmost positions and fewer in the left positions.

More errors in the center positions than in the end positions.

2. Short Term Memory – Working memory, place to hold information temporarily.

External sources- By way of the perceptual process.

Internal sources- The result of reasoning, decision making, and problem solving.

Encoding-

Information is encoded into a form

that can be conveniently stored

in human memory.

Some visual information is transferred

into auditory form.

Capacity and Duration-

Can hold about 6 units of information (Chunks)

People forget longer messages sooner- The shorter the code the better.

Try to limit interference.

Rehearsing

Retains information in short-term memory. Other activities should not interfere with the rehearsal process.

Divide longer strings of characters into groups of three or four to help rehearsal.

Ex. 217964831 217 964 831

Patterns

427947247 - > 427 947 247

24657435-> 24 65 74 35

NTH EDO GSA WTH ECA TRU

“The dog saw the cat run”

Serial Position

Errors will tend to occur in certain character positions more than others.

Ex. In a seven-character code

most errors tend to occur in the

fifth position and the fewest usually

occur in the first position.

7th Character

Auditory Stimuli – Last character tends to be recalled as well as the first character.

Visual Stimuli – Last character tends to be mistaken more often.

Conclusions for Designers

Don’t require users to retain

even a small amount of information

for over 20 seconds,

if rehearsal is not possible.

Figure 8-3

Figure 8-4

Primarily, we lose material from

short-term memory by replacing it

with new information.

New information seems to push out old

information.

Limited capacity – six or fewer units.

Relatively short duration – less than 20 seconds.

Page 151- Peg Words

3. Long - term memory – Permanent memory storage. Relies heavily on organization. Learning, remembering, forgetting

forgotten information – lost access to it.

Belief –People do not lose information permanently. Hypnosis

Three operations take place related to remembering and forgetting: Encoding, storage, and retrieval.

Encoding

Process of deciding how to classify information. Sometimes only the essence of what was sensed will be encoded.

Ex. Good movie, lousy dinner, nice guy

Storage

Storage – Putting information into long-term memory.

Retrieval

Search in different locations when

trying to remember something.

Try to recall how the information was

originally filed.

Forgetting

May be due to a failure of any of these three operations.

E.G. original coding may be incorrect,

info may be degraded during storage,

info may be difficult to retrieve

because searching is done in wrong place.

Interference

Proactive interference – material learned prior to the learning of new material may interfere with the use of the new material in a performance situation.

Exp. Learn Task A, Learn Task B, Perform B.

Y=MX+B, Y=A+BX Y=A+BX

Designers must find out what kind of responses have already been learned and then incorporate as much as possible the same kind of responses in the new system.

Retroactive interference –

Exp. Learn task A, Learn task B, Perform A

Lotus 1-2-3, Excel, Lotus 1-2-3

Recall Versus Recognition

Two commonly used ways of measuring remembered information.

Recalling info is much more difficult than recognizing info.

Designer should make full use of this fact.

Ex. ?

Memory Skill

MNEMONICS – Conscious ways for helping to ensure the retention of material that would otherwise be forgotten. Ex. String around your finger, complex visual imagery schemes

Cognitive performance aids- Require a person to either reduce or elaborate on information being received.

Reductions

Frequently take the from of acronyms:

Homes- Great Lakes

Roygbiv- Colors of spectrum

Ex. 9 times table, string around your finger

Disadvantage – Reduce the information so much

that it is no longer possible to reconstruct the original.

Figure 8-6

Elaboration

Adding information to make the material easier to remember.

Verbal Clues

By taking greater advantage of meaning that already exists in words, phrases, or concepts.

Every good boy does fine – lines of the Treble Clef.

Ex. Pi

Information that is coded along several dimensions is less likely to be forgotten.

Imagery Cues

A mental picture is created and viewed.

Man named S. memorized 50 numbers in 3 minutes.

Imagined a familiar street and he would place objects along the way.

• Designers should not put an unreasonable demand on human memory.

• Designers should develop interfaces that support an acceptable level of remembering.

• Provide facilitators (training, instructions, performance aids) that make full use of the MNEMONIC concept.

Design Implications