the human
o	Information i/o ...
-	visual, auditory, haptic, movement
o	Information stored in memory
-	sensory, short-term, long-term
o	Information processed and applied
-	reasoning, problem solving, skill, error
o	Emotion influences human capabilities
o	Each person is different
Vision
Two stages in vision
o	physical reception of stimulus
o	processing and interpretation of stimulus
The Eye - physical reception
o	mechanism for receiving light and transforming it into electrical energy
o	light reflects from objects
o	images are focused upside-down on retina
o	retina contains rods for low light vision and cones for colour vision
o	ganglion cells (brain!) detect pattern and movement
Interpreting the signal
o Size and depth
-	visual angle indicates how much of view object occupies
(relates to size and distance from eye)
-	visual acuity is ability to perceive detail
(limited)
-	familiar objects perceived as constant size
(in spite of changes in visual angle when far away)
-	cues like overlapping help perception of size and depth
Interpreting the signal (cont)
o	Brightness
-	subjective reaction to levels of light
-	affected by luminance of object
-	measured by just noticeable difference
-	visual acuity increases with luminance as does flicker
o	Colour
-	made up of hue, intensity, saturation
-	cones sensitive to color wavelengths 
-	blue acuity is lowest
-	8% males and 1% females colour blind 
Interpreting the signal (cont)
o	The visual system compensates for:
-	movement
-	changes in luminance.if wrong (different from actual system) errors can occur
Emotion
o Various theories of how emotion works
-	James-Lange: emotion is our interpretationof a physiological response to a stimuli
-	Cannon: emotion is a psychological response to a stimuli
-	Schacter-Singer: emotion is the result of our evaluation of our physiological responses, in the light of the whole situation we are in
-	Emotion clearly involves both cognitive and physical responses to stimuli
Emotion (cont.)
o	The biological response to physical stimuli is called affect
o	Affect influences how we respond to situations
-	positive -> creative problem solving
-	negative -> narrow thinking
"Negative affect can make it harder to do even easy tasks; positive affect can make it easier to do difficult tasks"
(Donald Norman)
 
Emotion (cont.)
o Implications for interface design
-	stress will increase the difficulty of problem solving
-	relaxed users will be more forgiving of shortcomings in design
-	aesthetically pleasing and rewarding interfaces will increase positive affect
Individual differences
o	long term
-	sex, physical and intellectual abilities
o	short term
-	effect of stress or fatigue
o	changing
-	age
Psychologyand the Design of Interactive System
o	Some direct applications
-	e.g. blue acuity is poor
blue should not be used for important detail
o	However, correct application generally requires understanding of context in psychology, and an understandingof particular experimental conditions
o	A lot of knowledge has been distilled in
-	guidelines
-	cognitive models
-	experimental and analytic evaluation techniques ."LTM - Storage of information
o	rehearsal
-	informationmoves from STM to LTM
o	total time hypothesis 
-	amount retained proportional to rehearsal time
o	distribution of practice effect
-	optimized by spreading learning over time
o	structure, meaning and familiarity - informationeasier to remember
LTM - Forgetting
decay
-	informationis lost gradually but very slowly
interference
-	new informationreplaces old: retroactive interference
-	old may interferewith new: proactive
inhibition
so may not forget at all memory is selective ...
... affected by emotion - can subconsciously   `choose' to forget
LTM - retrieval
recall
-	informationreproduced from memory can be assisted by cues, e.g. categories, imagery
recognition
-	informationgives knowledge that it has been seen before
-	less complex than recall - information is cue
Thinking
Reasoning :is a means of inferring 
 new informationfromwhatis already known
deduction, induction, abduction
Problem solving
Deductive Reasoning
o	Deduction:
- derive logically necessary conclusion from given premises.Touch
o	Provides important feedback about environment.