IST 110 Spring 2000 --- Lecture outline

January 20, 2000

This is annotated from Gerry Santoro's lecture

Focus on the Eye

Light sensitivity varies across the whole of the retina
• rods - sense B/W - very sensitive, used mostly in dim light, more frequent around retina periphery

• cones - sense color - not very sensitive, more frequent near center of retina

  Ex: amateur astronomers and peripheral vision

  Two eyes allow perception of depth

• the 'parallax' view is somehow processed by the brain into depth perception -- however it can be fooled

  **** Moon illusion article link here ******

• Some design issues relating to vision

   
  • color blindness (6% of men and 0.5% of women)
  • contrast and light sensitivity
  • location of displays and consoles
  • dependence on depth perception

  ---

Memory

Key notions:
• short term memory is limited to about 7 items

  Miller - "The Magic Number Sever Plus or Minus Two"

  so need to keep things short

 

• memory for future activities is prone to lapses and probably limited

   

• ability to recall is affected by encoding, retention and retrieval processes, and recognition is easier

   

• encoding is the ;laying down' of a memory. More meaningful processing at encoding seems to lead to longer, more reliable memories.

   

• retention is the interval between encoding and retrieval. Activites during retention can lead to forgetting.

   

• retreival depends on the information available to cur recall

   

• we can remember much more information when it is meaningful and when its meaning is processed at encoding time

Poorly understood but important:

 
• impact of interruptions

   

• memorization tasks other than 'rote list memorization'

   

• how systems can provide support for memory tasks

---

Attention

We can function without attending to information
• how else would we know to shift our attention?

open loop activities -- do not need constant monitoring (bike riding, skating, driving a car (somewhat), etc.)

closed loop activities -- constant monitoring required (typing an essay, singing a song, using a mouse, etc.)

Real human skills are a mixtrure of open and closed-loop behaviors.

VanRostroff effect (sp?) - put items in red to remember them better

---

Learning

Human learning is a poorly understood area with some controversy.

Key ideas:

 
• at least two kinds of learning - implicit and excplicit
   
  • implicit - based on practice, hard to verbalize (aikido, bike riding, dance, etc.)

    practice -- skill -- knowledge

     

  • explicit - based on hypothesis testing, easy to verbalize (accounting, computer programming)

    knowledge -- practice -- skill

  Key phenomena:

   
  • ability to recognize correct/incorrect preceeds ability to generate correct

     

  • knowledge is not acquired in all-or-nothing way

     

  • experts acquire rich repertoire of representations of their knowledge

---

Motor output

min times of about 150 ms

see fitts law for tracing

will vary by input method as well

 

Keystroke level model (from Card, Moran & Newell, 1983)

Time to perform a routine task by an expert is a combination of

Time to move hand to keyboard or mouse (if necessary) X if necessary

Mouse moves (based on distance and target perhaps) X number of moves

Time to type a key X number of keys

System response time

Thinking time (Mental operators) X number of operators

This gives +/- 20% accuracy

And is pretty consistent across designs

Advanced use can save approx $1Million/year for important applications (Gray, John & Atwood, 1993)

Gray, W. D., John, B. E., & Atwood, M. E. (1993). Project Ernestine: Validating a GOMS analysis for predicting and explaining real-world task performance. Human-Computer Interaction, 8(3), 237-309.