Cognetics and the Locus of Attention

The Humane Interface, Jef Raskin

Presented by: Dana L.Cobb

Human Performance Factors

• Are independent of a user’s age, gender, cultural background, or level of expertise

• Are are directly applicable to the foundations of any interface design

• Include such factors as ergonomics, cognetics, conscious/unconscious thought, locus of attention, habits, automatic tasks, absorption and the resumption of interrupted work

Design a human-machine interface in accord with the

abilities and foibles of humankind, and you will help the user not only get the job done but also be a happier,

more productive person.

Page 9-10

Ergonomics

• Ergonomics - The applied science of equipment design, as for the workplace, intended to maximize productivity by reducing operator fatigue and discomfort

• How does this apply to interface design?– “We must master an ergonomics of the mind if

we want to design interfaces that are likely to work well.”

Cognetics

• Cognetics - The study of the applicable, engineering scope of our mental abilities

• How does this affect interface design?– Much of the difficulty users encounter with

computers and related devices is due to poor interface design

Conscious and Unconscious

• Conscious - Having an awareness of one’s environment and one’s own existence, sensations and thoughts

• Unconscious - Mental processes of which you are not aware at the time they occur; information that is not being accessed but that can be recovered on demand

Conscious and Unconscious

• How does this apply to interface design?– Acknowledging these two distinct sets of

limited mental abilities and understanding how they work in relation to human-machine interfaces is essential to designing interfaces

– Designers must also recognize that a stimulus is used to trigger the migration of an item of information from the unconscious to the conscious

Properties of the Cognitive Conscious and the Cognitive Unconscious

Property Conscious UnconsciousEngaged by Novelty

EmergenciesDanger

RepetitionExpected EventsSafety

Used in New circumstances Routine situations

Can handle Decisions Nonbranching tasks

Accepts Logical propositions Logic orinconsistencies

Operates Sequentially Simultaneously

Controls Volition Habits

Capacity Tiny Huge

Persists for Tenths of seconds Decades (lifelong)

Focus versus Locus

• Focus - To direct toward a particular point or purpose (e.g. the object on a computer screen that is currently selected)

• Locus - A place, or site

Locus of Attention

• Locus of Attention - A feature or an object in the physical world or an idea about which you are intently and actively thinking (e.g. the one object, feature, memory, thought or concept upon which you are concentrating)

• However…each person sees and hears much more than just the locus of his or her attention

Locus of Attention

• How does this apply to interface design?– Designers must be cognizant of the user’s locus

of attention as well as their direct perceptions– Direct perceptions decay rapidly and do not

automatically become memories– Designers would be advised to only use

messages when the user can make immediate use of the message, or when the message will remain displayed until it is no longer needed

Habits

• Habit - A recurrent, often unconscious pattern of behavior that is acquired through frequent repetition

• Habits can become so strong as to reach a point of total loss of conscious control

• Habits CANNOT be undone by any single act of willpower

Habits

• How does this apply to interface design?– Persistent use of any interface will cause the

user to develop habits– Interfaces must be designed in such a way that

they do not allow the user’s development of habits to cause problems

– Designers must be cognizant of the helpful and injurious properties of habit formation

Habits

• To Do:– Deliberately take advantage of the human trait of

habit development– Allow users to develop habits that smooth the flow

of the work

• To Avoid:– Many options to accomplish the same task– Two or more heavily used applications that differ in

only a handful of often-used details

Simultaneous Tasks

• Tasks performed simultaneously may include:– One primary task that is NOT automatic which

requires your locus of control– One or more tasks that are automatic– If two tasks are being performed, neither of

which is automatic, performance on both tasks will degrade (referred to as interference)

Simultaneous Tasks

• How does this apply to interface design?– Designers must recognize and account for the

inevitability of habit formation– Safety measures may be rendered useless by

habituation– Key idea: any confirmation step that elicits a

fixed response soon becomes useless

Absorption

• Users have only one locus of attention; a user cannot attend to multiple simultaneous stimuli

• When a user’s locus of attention shifts, it is because he has lost the old and acquired the new (there cannot be two)

• An intense focus will require a greater stimulus to affect a change

Absorption

• How does this apply to interface design?– The goal of interface design is to leave the task

as the locus of the user’s attention– Systems should be designed to allow users to

concentrate on their jobs– Interfaces should be designed to work, regardless

of the user’s state of absorption– Make sure that users cannot make interface

operation errors

Exploitation of Absorption

• When a user’s attention is fixed, changes can be made elsewhere in the system without distracting the user

• Interfaces can be carefully designed to “mask” tasks occurring in the background– Example, Canon Cat

Interrupted Work

• The resumption of interrupted work may:– Be uninhibited if the interruption lasts only a

few seconds (within the decay time of short-term memory), or

– Need a “trigger” to prompt the resumption if the delay was significant

Interrupted Work

• How does this apply to interface design?– Designs are optimal when they return a user to the

point where he or she left off• Return user to the last web page viewed, rather than

the home page

• Return user to the place in a document where he or she was last working when it was closed or saved, rather than the uppermost left corner

– Computers already have the necessary hardware to accomplish this

Questions/Discussion

• What do you think is a more important consideration in interface design, conscious or unconscious thought?

• Why do applications continue to use delete confirmation when acceptance of the confirmation has become so routine (and thus risky? What would be better?

• Why aren’t applications like Word designed to open at the point where you left off?