Chapter 5 Memory 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

Patterns > > 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.

7 th 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

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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.

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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