Human Computer Interaction
Human-computer interaction (HCI) is a multidisciplinary field of study focusing on the design
of computer technology and, in particular, the interaction between humans (the users) and
computers. While initially concerned with computers, HCI has since expanded to cover almost
all forms of information technology design.
INPUT–OUTPUT CHANNELS:
A person’s interaction with the outside world occurs through information being received
and sent: input and output
Input in the human occurs mainly through the senses and output through the motor
control of the effectors.
Similarly there are a number of effectors, including the limbs, fingers, eyes, head and
vocal system.
Vision …Human eye…..Visual perception and angle its types …..Human Ear..and detail
are on book (pg-16 to 26) and also concern to the Slides given by Sir Naveed.
Movement:
A simple action such as hitting a button in response to a question involves a number of
processing stages. Each of these stages takes time, which can be roughly divided into reaction
time and movement time. Movement time is dependent largely on the physical characteristics of
the subjects: their age and fitness, for example. Reaction time varies according to the sensory
channel through which the stimulus is received. Speed and accuracy of movement are important
considerations in the design of interactive systems, primarily in terms of the time taken to move
to a particular target on a screen.
Movement time = a + b log2(distance/size + 1)
HUMAN MEMORY:
Our memory contains our knowledge of actions or procedures. It allows us to repeat actions, to
use language, and to use new information received via our senses. It also gives us our sense of
identity, by preserving information from our past experiences. It is generally agreed that there
are three types of memory or memory function:
i) Sensory buffers,
ii) Short-term memory or working memory, and
iii) Long-term memory.
Sensory memor: The sensory memories act as buffers for stimuli received through the
senses. A sensory memory exists for each sensory channel: iconic memory for visual
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stimuli, echoic memory for aural stimuli and haptic memory for touch. These memories are
constantly overwritten by new information coming in on these channels.
Buffers for stimuli received through senses
o iconic memory: visual stimuli
o echoic memory: aural stimuli
o haptic memory: tactile stimuli
Examples
o “sparkler” trail, finger moving
o stereo sound
Attention
Attention is not possible in the absence of consciousness, The activity of
concentrating mind on a particular matter is called attention.Attention is an active part of
consciousness.
Attention is the concentration of consciousness upon one object rather than others – Dumvile
Types of Attention:
Short-term memory
Short-term memory or working memory acts as a ‘scratch-pad’ for temporary recall of
information. It is used to store information which is only required fleetingly.
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Display format should match memory system used to perform task
New info can interfere with old info
Scratch-pad for temporary recall
rapid access ~ 70ms
rapid decay ~ 200ms
limited capacity - 7± 2 chunks (chunk formation called “closure”)
Memory flushing
ATM machine provides ATM card to user before cash
Recency effect
o better recall for items at the end of the list because these items are still active in
STM (and possibly SM) at time of recall
Primacy effect:
o better recall for items at the beginning of the list (because these items have been
rehearsed more frequently than other items and thus have a greater chance of
being placed in LTM)
Long-term memory:
Organized as a network of connected chunks of knowledge
active chunks are in the working memory
activation spreads through the network
strength of connection
retrieval of items into WM
Repository for all our knowledge
slow access ~ 1/10 second
slow decay, if any
huge or unlimited capacity
Episodic memory
Events & experiences in serial form
Helps us recall what occurred
Semantic memory
Structured record of facts, concepts & skills
One theory says it’s like a network
Another uses frames & scripts (like record structs)
Semantic memory structure
provides access to information
represents relationships between bits of information
supports inference
Model: semantic network
inheritance – child nodes inherit properties of parent nodes
relationships between bits of information explicit
supports inference through inheritance
LTM processes
3 processes
Storage
Forgetting
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Information retrieval
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