Psychological Issues in HCI - CM212/CM304

Nick Gibbins
MMRG

Overview

• Cognition
• Human Information Processing
• Perception
• Attention
• Memory

Cognition

The process by which we become acquainted with things or gain knowledge.

Human Information Processing

Sequential four-stage process:

1. encode stimulus from the environment into internal representation
2. compare encoded stimulus with memorised representation
3. formulate response to encoded stimulus
4. take action

Perception

"Perception is the immediate discriminatory response of an organism to energy activating sense organs ... To discriminate is to make a choice reaction in which contextual condition play a deciding role"
(Bartley, 1969)

"The term perception refers to the means by which information acquired from the environment via the sense organs is translated into experiences of objects, events, sounds, tastes, etc."
(Roth, 1986)

Perceptual Modalities

A modality is an `avenue of sensation'.

Several are important to a study of interface design:

visual

most important to interface design

sound

touch

used in multimedia and virtual reality

Perception Classes

Two main approaches to perception:

• Constructivist
• Ecological

Constructivist Perception

World view constructed from information in the environment and previously stored knowledge.

"We are so familiar with seeing, that it takes a leap of imagination to realize that there are problems to be solved. But consider it. We are given tiny distorted up-side-down images in the eyes, and we see separate solid objects in surrounding space. From the patterns of stimulation in the retinas, we perceive the world of objects, and this is nothing short of a miracle."
(Gregory, 1978)

Constructivist Perception Concepts

context

used to resolve ambiguous stimuli

gestalt:

innate laws of organisation

Ecological Perception

Allows information to be picked up rather than processed.

Much higher level model than retinal images, dealing with movements, surfaces, optic flows, etc.

"This is a radical hypothesis, for it implies that the `values' and `meanings' of things in the environment can be directly perceived."
(Gibson, 1979)

Ecological Perception Concepts

affordance:

a possibility for action afforded to a perceiver by an object

Extending the Human Information Processor

Cognition is viewed in terms of:

• how information is perceived
• how information is attended
• how information is processed and stored

Attention

"Everyone knows what attention is. It is the taking possession of mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought ... It requires withdrawal from some things in order to deal effectively with others"
(James, 1890)

Attention Concepts

• Focused attention
• Divided attention
• Several techniques for guiding attention
  • structure information
  • use spatial or temporal cues
  • use colour
  • use alerting techniques

The Multi-store Model of Human Memory

Sensory Registers

Modality-specific temporary buffers.

Encoding:

physical (unprocessed)

Latency:

200 msec (visual) 1.5 sec (audible)

Working Memory

`active' memory

Encoding:

acoustic or visual

Capacity:

7 +- 2 chunks

Latency:

~ 7 sec

Latency depends on the number of chunks in active memory.

Long Term Memory

Encoding:

semantic

Capacity:

unlimited?

Latency:

unlimited?

Memory Concepts

priming:

recall is affected by prior information (facilitation,interference)

gist:

redundant information is ignored

elaboration:

existing knowledge used to elaborate the content of memory

inference:

existing knowledge used to derive new knowledge

Knowledge Representation

analogical:

close correspondance between represented and representing world (mental images, etc)

propositional:

set of discrete symbols, concepts, propositions, objects, relations

procedural:

knowledge of actions, directly interpreted by action system

General Implications

• Human processing capability is very small
• Constant danger of overload

Design Implications

Interface designers should:

• use meaningful/familiar chunks
• simplify decision making
• minimise short term memory storage

Graphical Representation

Characteristics of information on the screen should be the same as in the environment.

• image generation is expensive
• high degree of realism is often unnecessary

Graphical Modelling

size:

closer objects appear to be larger

interposition:

objects block our view of other objects

contrast, clarity, brightness:

near objects are sharp, far objects are dull

shadow:

relative position cue

texture:

closer objects are grainier

parallax:

close objects move faster than far objects

Graphical Coding

Graphical representation of:

• abstract system processes
• data objects
• other interface features

mapping:

icons resemble the objects they represent at the interface

Iconic Representation

resemblance:

depicts through an analogous image

exemplar:

serves as a typical example

symbolic:

conveys an underlying referent that is at a higher level of abstraction than the image

arbitrary:

bears no resemblance to the underlying concept

Colour and Interface Design

Colour coding aids some cognitive tasks:

• division of display into regions
• useful for search tasks
• less useful for organisation or categorisation
• more useful in search tasks for inexperienced users
• too many colours increase search time colour pollution

Attention and Interface Design

cognitive aids:

external representations to gain attention relevant to the task that needs to be performed

• provide information about the status of an activity
• remind user of their position before they were distracted
• notify user of background tasks

Memory and Interface Design

Remembrance depends on meaningfulness.

familiarity:

frequency of occurrence in environment

imagery:

ability to elicit mental images

Familiar words or images can be confusing in the computer field.

A Broader Cognitive Framework

Since the mid 1980s, there has been a move away from information processing frameworks in cognitive psychology.

Alternative approaches have been developed which situate cognitive activities within the context in which they occur.

Distributed Cognition

Explains cognitive activities as embodied and situated within the context in which they occur.

actors:

entities across which cognition is distributed

functional system:

collection of actors and their relations in the environment

Aims to analyse coordination of components of functional system and explain breakdowns in this coordination.

Suggested Reading

• J. Preece et al Human Computer Interaction, Ch.3,4,5
• P. Johnson Human Computer Interaction: psychology, task analysis and software engineering, Ch.2,3,4
• V. Bruce and P.R. Green Visual Perception: physiology, psychology and ecology, Ch.10