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CSCD 487/587Human Computer Interface
Winter 2013
Lecture 8Human Movement and Memory
Overview
Few more thoughts on humans and their abilities
How do movements relate to interface design?
How much information can we deal with?
How complex should the information be on a screen?
Look at movements, and memory
Human Memory
Human MemoryBasic Questions How does information get into memory? How is information maintained in memory? How is information pulled back out of memory?
Three processes– Encoding, Storage and Retrieval
Figure 7.2 Three key processes in memory
Memory Encoding
Encoding is crucial first step to creating a new memory
It allows perceived item of interest to be converted into a construct that can be stored within brain,
Recalled later from short-term or long-term memory.
Memory Encoding
Encoding is a biological event beginning with perception through senses
Process of laying down a memory begins with attention
Memorable event causes neurons to fire more frequently, making experience more intense and increasing likelihood that event is encoded as memory
Memory Encoding Perceived sensations are decoded in
various sensory areas of cortex, and then combined in brain’s Hippocampus into one single experience
Hippocampus is then responsible for analyzing these inputs and deciding if they will be committed to long-term memory
It acts as kind of sorting center where new sensations are compared and associated with previously recorded ones
Various threads of information are then stored in various different parts of the brain,
Figure 7.23 The anatomy of memory
Storage: Maintaining Information in Memory Information storage in computers is similar Information storage in human memory
Subdivide memory into 3 different stores• Sensory,
Iconic - visual stimuli
Echoic - aural stimuli
Haptic - touch stimuli• Short-term,• Long-term
Figure 7.7 The Atkinson and Schiffrin model of memory storage
Sensory Memory Shortest term memory
Retain impressions after original stimulii ended
Ultra short memory decays quickly 1/5 to ½ second
Is the first step to storing in short term memory
Information is passed to short term memory via attention
Placing attention on it filters stimuli that is of interest
Short Term Memory Next in line from sensory memory
Scratch pad for temporal recall Brain's post-it notes, holds small amount
of information 7 + or – 2 items Recall for short period of time, 10 – 15
secs Example: To understand an entire
sentence when you read it, hold beginning of sentence in short term memory
Next step towards long-term memory One way to transfer to long-term storage Working memory is short term memory
Short Term Memory
If memory is to be stored in long-term memory some type of transfer takes place in few seconds
Rehearsal – the process of repetitively verbalizing or thinking about the information
This is where chunking takes place to help with memory recall:
Long Term Memory Memories come to Long-term storage
through short term storage Process of consolidation by rehearsal
and meaningful association Encodes information semantically Process involves physiological changes
to brain – neural networks are created With repeated use, efficiency of neural
networks increases Storage occurs throughout brain
Slow access - 1/10 second Slow decay, if any Huge or unlimited capacity
Long-term MemorySemantic 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 information - explicit Supports inference through inheritance
works sheephas four legs
barks ANIMAL is a SHEEPDOG
breathes is a DOG
moves has tail is a
is a size: medium COLLIE
color: [brown/white, black/white, merle]
HOUND instance instance
tracks is a LASSIE
SHADOW
film character size: small
BEAGLE color: brown/whitebook character color: brown/white
color: [brown, black/white] instance
SNOOPY
cartoon/book character friend of
CHARLIE BROWN
Semantic network model of LTM
Other Models of Long Term MemoryFrames:Information organized in data structureSlots in structure are instantiated with particular values for a given instance of data. DOG
Fixed
legs: 4
Default
diet: carnivorous
sound: bark
Variable
size:
color
COLLIEFixed breed of: DOG type: sheepdogDefault size: 65 cmVariable color
Script for a visit to the vet
Entry conditions: dog ill Roles: vet examines vet open diagnoses owner has money treats owner brings dog in paysResult: dog better takes dog out owner poorer vet richer Scenes: arriving at reception waiting in room examination Props: examination table paying medicine instruments Tracks: dog needs medicine dog needs operation
Other Models of long-term Memory
Scripts:Model of stereotypical information required to interpret situation or language.
Accessing MemoriesRetention – the proportion of material
retained Recall Recall is a way that you obtain
information from your memory without having a cue to prompt the response. You have to essentially draft the information without any assistance.
Recognition Recognition is how you respond to a sensory cue. You look at something and your mind looks to see if what you are seeing in front of you matches anything that has been stored. If you notice a match, you are recognizing the information.
Example: Taking a test, multiple choice is recognition, short answer is recall
Figure 7.16 Ebbinghaus’ forgetting curve for nonsense syllables
Figure 7.17 Recognition versus recall in the measurement of retention
Long Term Memory How do we forget information?
When neural networks become weak from lack of use
When we impose new neural networks on top of old networks causing interference with old network
Memory is selective and affected by emotion - can “choose” to forget
Also varies by sex, physical and intellectual abilities
Changes with age
Figure 7.19 Retroactive and proactive interference
Memory Implications for Design
26
Recognition over Recall
As we said ...Recall
Info reproduced from memory, no cuesRecognition
Presentation of info provides knowledge that info has been seen before
Easier because of cues to retrievalWe want to design UI's that rely on recognition!
Short term Memory Limits
Misconception that limited short-term memory should be limited to 7 items!!!
It's fine to have longer menus (if needed)– Users don't have to memorize the full
list of menu items The entire idea of a menu is to rely on
recognition rather than recall But if you make a menu too short, the
choices become overly abstract and obscure.
Specifically for Web Design
Response times must be fast enough that users don't forget what they're in the middle of doing while waiting for the next page to load
Change color of visited links so that users don't have to remember where they've already clicked
Also counts as providing feedback to users
Specifically for Web Design
Offer help and user assistance features in the context where users need them
So they don't have to travel to a separate help section and memorize steps before returning to the problem at hand
This goes for other non-web interfaces too
Individual Differences
Huge individual differences in user performance
Top 25% of users are 2.4 times better than the bottom 25%
Only about 4% of the population has enough brainpower to perform complex cognitive tasks such as making high-level inferences using specialized background knowledge
If you forget these limits, users will find your site very frustrating
Measuring Motor Movement
Movement – Fitt’s Law• Fitts' Law, 1954
–Fundamental law of human sensory-motor system–Practical application in interface design–Describes the time taken to hit a screen target
–Time, Mt, to move hand to a target of size, S, at distance, D, away
Mt = a + b log2(D/S + 1)
where: a and b are empirically determined constantsMt is movement timeD is Distance S is Size of target
– “index of difficulty”: log2(D/S + 1)• Same performance at greater distance with greater size
targets as large as possible, distances as small as possible
Fitt’s Law
Which is the easiest to hit?
HIT MEHIT ME
4 cm 4 cm
1 cm
5 cm
T = 100 log2(4/1 + 0.5) = 9 ms
T = 100 log2(4/5 + 0.5) = 2.6 ms
34
Fitts’ Law Example
Which is the easiest to hit?
TodaySundayMondayTuesday
WednesdayThursday
FridaySaturday
Pop-up Linear Menu Pop-up Pie Menu
Fitt’s Law Implications
• Hierarchical menus are hard to hit– Especially when it takes two actions …
Take a Quiz
Try out Fitt's Law Concepts from AskTog
http://www.asktog.com/columns/022DesignedToGiveFitts.html
Summary
Human memory models important – Otherwise, we as designers will
underestimate or overestimate our users
– Users will get frustrated if their mental capacities are not accounted for in products they use !!!
References
Short-Term Memory and Web Usability by J. Nielsen
http://www.nngroup.com/articles/short-term-memory-and-web-usability/
Human Memory
http://www.human-memory.net/brain_parts.html
The End
Reading … on to Chapter 4