Design Considerations
Requirements Gathering
Envisionment Methods
Evaluation
Other
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Memory
An understanding of memory is one of the most important aspects of human
information processing for those concerned with the development of human-computer
systems. Like so much of human psychology, memory is a fascinating and highly
complex subject. For the student of HCI it is of the utmost importance that
the users memory is not over taxed.
Memory Systems
There are three basic types of memory systems:
- working memory
- long term memory
- sensory memory
Working Memory
- Working memory is the area of conscious memory where current processing
takes place - Think of it as the ‘processor’ part of a computer
- It can be fed by memories stored in long term memory, or by sensory
input.
- WM has a role to play in both language understanding and calculation.
- In both these cases there is a need to hold information in your head
while the process of interpretation of the words or calculation is being
carried out.
- STM is an aspect of working memory (WM).
- Short term memory (STM) is as an area of memory that is able to hold
limited information for a short time.
- STM was thought to be limited to the ‘magic number’ 7 plus
or minus 2 pieces of information - Miller’s magic number
- Later research suggests that the capacity of working memory is only
about 3 or 4 items - words, phrases or images
Phonological Loop
- like a loop of audio tape.
- e.g. when trying to dial an unfamiliar phone number, tend to repeat
the numbers
- limited capacity and duration - < 30 seconds unless refreshed
Visuo-Spatial Scratch Pad
- visuo-spatial scratch pad is the visual/spatial equivalent of the phonological
loop
- e.g visualising a route through a town, building, menu
Long Term Memory
- Long term memory (LTM) is an area of memory where information is stored
and can be retrieved over very long periods of time - Think of it as the
‘hard drive’ of a computer.
- LTM is effectively infinite.
- Items from LTM have to be retrieved and brought into working memory
before they can be used - This is called activation.
- Items in working memory can be processed more easily than information
that has to be retrieved from LTM, thus any system that requires recall
from LTM will slow down the activity of the user.
- The inability to retrieve information as desired, what is termed forgetting,
could be viewed as very long retrieval times.
- Electrical stimulation of the brain has been said to evoke long-lost
memories.
Examples of LTM
- autobiographical memory - what I did on my first day at school
- procedural memory - e.g. the knowledge of how to ride a bike or use
Word
Sensory Memory
- Sensory memory is an area of conscious memory that deals with information
from the senses – eyes, ears, tongue, nose & haptic (touch).
- When we watch a film we ‘see’ thousands of still frames,
which are converted by our brain into a moving image.
- Other examples include light traces and audio play-back.
- As yet, computer systems do not use taste or smell, however in the future
virtual reality systems may wish to use them in order to create the atmosphere
of a real experience.
Examples of Sensory Memory
- auditory encoding, e.g. music
- haptic encoding, e.g. the sting of a burn
- olfactory and gustatory encoding, e.g. identifying fresh and rotten
food
Types of Memories
There are two basic types of memories
Episodic Memory
Episodic memory involves memory of events – what you had for dinner,
what you did last weekend.
Semantic Memory
Semantic memory is knowledge about the world – what different words
mean, how many inches in a foot.
Forgetting
- accessibility - retrieving information, main problem for long term
memory.
- availability - whether stored or not, main problem in working memory
- Imagine trying to find a specific book in a library
- you find it (memory is retrieved)
- it’s not in the library (memory is unavailable)
- it’s in the library but has been mis-shelved (not accessible)
- Working memory
- decay - memory simply fades with time
- displacement - working memory limited in capacity: if try to add
another item or two, a corresponding number of items are squeezed
out
- Also a number of clinical conditions affecting different aspects
of memory
- Long term memory
- Disuse - no evidence to support this
- Interference - forgetting influenced by what we have done before
or after learning for example moving from word processor version I
to version II - version II has reorganised menus. Having learned version
I interferes with learning version II
- Retrieval failure
Memory Experiments
The Digit Span
- The subject is presented with a series of digits and asked to repeat
them back in the same order.
- The number of digits is gradually increased until finally the subject
always fails to recall the list accurately.
- The sequence length at which the subject is right half the time is the
digit span.
Exercise - Digit Span
Conduct the digit span experiment on a partner and have them do it to
you using the second list. Call out each line of numbers and have your partner
repeat them immediately. Record the results and derive your digit span.
The sequence length at which the subject is right half the time is the digit
span.
- digit span 1
- digit span 2
Chunking
- Experiments have shown that the capacity of STM is 7 ± 2 (may
be outdated).
- More information can be remembered in information that is chunked.
- For the computer designer, this means that it would be inadvisable
to require the user to recall more than this amount of information.
- Also, passwords of more than 5 to 9 characters are inadvisable unless
chunking is possible.
- Example, remembering the number 051594737 is easier if remembered in
this form: 051 – 594 – 737, as a telephone number. That is,
remembering 3 chunks, instead of 9 individual numbers.
- Similarly the letters HMSEDIODUA are more easily remembered as HOUSEMAID
(HOUSE and MAID make 2 chunks)
Recalling
- Recalling lists in any order is known as free recall.
- In these experiments, there is a tendency for the first one or two words
to be remembered well – this is called the primacy effect. These
words tend to be rehearsed and enter LTM.
- Words in the middle will be remembered less well, and
- those at the end will be remembered well. This is called the recency
effect.
- The words at the end are remembered well because they are either still
in the auditory loop or in WM.
- Rare words are less likely to be remembered than common words.
- Words that have associated images (like elephant) tend to be remembered
better.
Exercise - Recall
Choose a list at random from the 4 below and call the words out slowly
and steadily to a partner. Have the partner repeat the list in any order
and tick off the words. Do you notice any pattern? Have your partner repeat
the experiment on you with a different list.
- Recall List 1
- Recall List 2
- Recall List 3
- Recall List 4
The Stroop Effect
- Trying to read the words at the same time as processing their (counter-intuitive)
meaning
- normally presented as a series of colour coded words, with each word
reading a colour different to their actual colour
Exercise - Stroop Effect
The link below goes to an interactive stroop experiment. Try to read the colour without being affected by the meaning of the word.
- Stroop effect experiment
Guidelines for Interfaces
Consistency
- User interfaces need to be consistent.
- The user should not be expected to remember a different sequence of
events for similar actions.
- The user interface should behave in consistent ways at all times for
all screens
- Terminology, icons and use of colour should be consistent
- Examples:
- Keyboards are similar in form and structure to the typewriters
they evolved from;
- The date format should be presented to American users in the form
mm/dd/yy and to European user in the form dd/mm/yy
Cues & Feedback
- Human beings like to know when a task is done since they are now free
to move onto the next stage and forget about what they have just done.
This is called closure.
- It is important to build closure into systems since this acts as a means
of allowing processes to be grouped or chunked in memory.
- The process later becomes a whole chunk for the expert user.
- The act of providing feedback is also a means of giving feedback to
the novice user, aiding the learning process.
- Visual and audible clues should be given when a user is succeeding
in the task as well as erring
- Provide reminders, or warnings as what stage an individual is at in
an operation.
- Provide ongoing feedback on what is and/or just has happened.
- Example:
- computers beep when an error is made.
- When we copy a file, we see an icon representing the file in a new
position in the file manager as well as an alert box signalling the
copying process if the file is large.
Recognition Versus Recall
- Use picklists when trying to recall something which is on the tip of
the tongue or ambiguous (one of the London airports) or
- when spelling is difficult
Persistence
- To minimise the load on working memory, use persistence, so do not flash
important information onto the screen for brief time periods.
- Get the user to click ‘OK’ – even if she does not
think that it is.
- ‘OK’ is this instance really means – ‘I acknowledge
the message’
Reducing Load
- Supporting memory by prompts reduces load
- use wizards to prompt the user and to help recall steps to complete
a task
- user need only supply relatively small amounts of information at
any one time
- has the advantage of an error correction system (i.e. use of the
back and next steps)
- Organise information into a small number of "chunks"
- Try to create short linear sequences of tasks
- Organise data fields to match user expectations, or to organise user
input (e.g. the auto-formatting phone numbers)
- Do not ‘overwrite’ the contents of working memory by giving
additional tasks to the users
Using Images
- There is evidence to suggest that humans recall pictures better than
they can recall words.
- This has led to the development of iconic interfaces, rather than command-line
interfaces.
Other
- A user interface must encourage a relaxed attitude since users are more
likely to succeed with the system if they are not under stress.
- People are more likely to recall information if they are in the same
situation in which it was learned
Further Reading
- Anderson, J. (1995) Learning and Memory
- Baddeley, A. (1994) Your Memory: A User’s Guide
- Gleitman, H. (1992) Basic Psychology
- Rose, S. (1992) The Making of Memory