Cornell University Ergonomics Web
DEA 3250/6510 CLASS NOTES
Information Processing
Information - is
key to survival and success. We receive information about the external world
through our senses (exteroceptors) and we receive information about our
own internal state through interoceptors (e.g. kinesthetic feedback from
joints, proprioceptive feedback from muscles). Information is processed
by the brain.
A. Quantification of information - The brain is an active information
processor that filters incoming information and has processing limits.
- Definition of information - Information can be described simply as the reduction
of uncertainty.
- Information and Probability - Highly probable events convey little information, they
merely confirm what is anticipated. Highly improbable events convey more
information. (The unusual gets attention.)
B. Information Theory - provides a quantitative way of measuring
information.
- Measurement -
Information is measured in bits (H). A bit is the amount of information
required to decide between two equally likely alternatives. Uncertainty
is choice; the more options given, the more difficult it is.
Hick's Law (1952) - If probabilities are equal, the amount of information
needed to decide is:
H= log 2 (n+1)
H= info log 2 =
the "bit" binary digit n= number of choices
Hick's Law for Unequal Probabilities (Hyman, 1953) - If probabilities
are unequal, the amount of information needed to decide is:
H=SUM(i-1 to i=n)( pi log2 (1/pi+1))
Speed of Reaction - For events with equal probability subjects gain
information at a constant rate so there is a linear increase in the speed
of reaction.
(i) Simple Reaction Time (SRT) - is the time needed to make one choice.
This will change depending on your state, e.g. drunk or tired. The
time can be up to 1/5 second. The speed of reaction depends on the modality
(vision, hearing etc.)
(ii) Complex Reaction Time (CRT) - is the time needed to make one
choice from either several signals or choose from several choices. The speed
of CRT depends upon the number of choices and is always longer than the SRT
for the same modality.
(iii) Types of Information - The brain will cope with different types
and quantities of information in different ways. (e.g. auditory information
can be shout-out by covering the ears, visual information can be shut out by
closing the eyes).
- Redundancy - allows
us to interpret missing information more easily. The English language is
68% redundant which allows us to interpret missing information easier.
The formula for finding percent of redundancy:
% redundancy = (1-(H average/Hmaximum)) x 100
C. Conflicting Information (Illusions)- Illusions can occur when the brain tries to make sense
out of conflicting information or when the brain adds information based
on experience (or cultural conventions) which isn't based on reality. Examples
of illusions are the: Muller-Lyer illusion, Ponzo illusion, Necker cube,
Stroop effect (e.g. the word "red" but printed in a different
color), conceptual incompatibility (e.g. exit signs are sometimes red, sometimes
green without clear human factors standards).
Human Information Processing
- Attention Resources
- Short term sensory storage - Automatic, temporary storage for each sensory channel.
Mechanisms - Two mechanisms prolong stimuli representation for further
processing:
Visual Storage (Iconic) - Visual representation is stored for less
than 1 second.
Auditory (Echoic) - Degraded image of reality can last a few seconds.
- Perception and response
- Short term memory storage - lasts a few seconds
- Decision making
- Working memory -
Attention resources must allocated toward the process of retaining a memory.
- Memory - There
are two types of memory - working memory and long-term.
a. Working Memory -
Encoding - There are three types of encoding
Visual -
Phonetic - Auditory presentation. Both visual and auditory representations
of stimuli can be generated by stimulated by the other type of stimuli
or by long term memory (e.g. read a word (visually) or sound a word out
(auditorily).
Semantic - Abstract representation of meaning. Need to present information
without ambiguity so people can code the correct meaning.
Storage - Meaning determines how the semantically coded information
will be stored. If information is misunderstood it is improperly stored.
Capacity - Short term memory storage capacity is around seven, +/-
2 pieces of info.
Chunking - Chunking information into short meaningful "phrases"
aids in storage. An example of "chunking" a string of letters
would be to break them down into meaningful pieces: HPIBMUSJFK - HP IBM
US JFK
- Mnemonic Devices -
are aids that help us remember things, e.g. ROYGBIV - (e.g. a mnemonic could
be "Richard of York Gave
Battle In Vain" to represents the color spectrum).
- Mind Mapping - a
method developed that uses diagram drawing to reinforce associative links
between information items.
- Serial Position Effect
- It is much easier to remember items which occur at the beginning or end
of a series rather than items in the middle. Research has shown that when
visiting museums people read exhibits at the beginning and end and are
more lackadaisical in the middle.
- Semantic Analysis
- We generally encode memory in an abstract manner, e.g. remembering theme
of short story. In the knowledge representation structure, meaning comes
from content
- Long Term Memory -
influences/guides perceptual processes, pattern recognition processes,
etc
- Transferring Information - Semantic coding mainly transfer information from working
memory so when you understand something its easier to remember
- Weakest Link -
is retrieving from long term memory is the weakest link in the system
- Understanding Information - We assume stimulus info will be organized some way.
- a. Pattern Recognition -
The Pandemonium Model of how the brain recognizes patterns and analyzes
features (Oliver Selfridge, 1959):
- Sensory Input -
Can be broken down into several representations (demons). Whichever demon
"shouts" the loudest (is the closest match) gets chosen.
- Image Demons -
record the external image.
- Feature Demons -
extract features looking for particular characteristics and patterns.
- Cognitive Demons
- recognize one pattern by combining inputs from feature demons.
- Decision Demons -
choose the identification of the pattern.
- Signal Detection (Model) Theory - The brain is always active. There is information and extraneous
(meaningless) "noise" in central nervous system.
- Reactions to Stimuli -
are numerous:
- Hit - Signal
is recognized when present.
- False Alarm -
Signal is detected when it's not present.
- Miss - No
signal is identified when it is present.
- Correct Rejection -
No signal is identified when the signal wasn't present.
Example -
If a pilot speaks to air traffic control and says "mayday" and
air traffic controller correctly recognized the word it is a "Hit".
If, however, the pilot said "heyday" and the air traffic controller
heard "mayday" then it is a "false alarm".
- Response Criterion -
There is a subjective critical level, whenever sensory activity is judged
to exceed this criterion the signal is judged to be present.
- Factors affecting Response Criterion (B) - Criterion is the ratio of signal to noise (i.e. height
of the signal curve over the height of the noise curve).
(i) As the probability of observing the signal increases, the criterion
decreases.
(ii) As the costs of a false alarm increase, criterion increases.
(iii) As the benefits of a hit and costs of a miss increase so criterion
decreases.
- Sensitivity (d')
- The keeness or resolution of the sensory system is its sensitivity. The
sensitivity is the distance between the two distributions.
Consequently - may miss call unless you're expecting it
, moving criteria, lots of false starts,
want to separate distribution (rates), want to minimize false alarm and
miss rate,
performance starts to deteriorate when we're tired
4. Improving Performance -
a. To improve performance on a selective attention task -
- Use as few channels as possible; even if signal
rate per channel is increased.
- Provide users with information on the relative
importance of various channels so that attention resources can be correctly
allocated.
- Decrease overall level of stress to allow more
channels to be sampled.
- Give user some preview information as to where
future signals will occur.
- Train user with optimal scan patterns.
- Put multiple visual channels close together.
- Ensure that multiple auditory channels don't
mask each other.
- Where signals require individual responses separate
these by as much time as possible (> 0.5 secs.). Also allow user to
control rate of stimuli input.
b. To improve performance on a focused attention
task-
- Make competing channels as distinct as possible
from the channel to be attended to.
- Separate competing channels in space.
- Decrease the number of competing channels (distractions).
- Make channel to be attended larger, brighter,
louder, and centrally located.
c. To improve performance on a divided attention
task -
- Decrease number of potential sources of information.
- Give information on relative priorities between
tasks to decrease time-sharing stress.
- Keep task difficulty as low as possible.
- Make tasks as dissimilar as possible in terms
of information processing, input/output modalities, and memory codes.
- For time-shared manual tasks, the greater the
learning of the motor task the less its effect on performance.
d. To improve performance on a sustained attention
task -
- Choose appropriate task variation and work-rest
schedule.
- Increase the conspicuousness of the signal (larger,
more intense, longer duration, more distinctive).
- Decrease the uncertainty as to when and where
the signal will occur.
- Give operators feedback on detection performance.
- Give adequate training on signals to be identified.
- Improve motivation and emphasize importance of
performance.
- Decrease the rate of stimulation presentation
if high.
- Maintain noise, temperature, illumination, and
other environmental factors at optimal levels.
e. To decrease the effects of aging on information
processing -
- Strengthen signals; make them louder, brighter,
etc.
- Design controls and displays to decrease irrelevant
details that would act as noise.
- Design a high level of conceptual, spatial, and
movement compatibility.
- Decrease timesharing demands.
- Let person control task pace or give them time
between execution of response and signal for next response.
- Allow more time and practice for initial learning.
Back to DEA 3250/6510 menu