3. Memory and Human Computer Interaction

Memory memory 4 The multi-store model of memory describes how the processes of the stage model of HCI are interconnected 4 Main characteristics of this model are: buffer –sensory buffer –short-term –short-term memory store (STM) –long-term –long-term memory store (LTM) –low capacity channel –low capacity channel from STM to LTM

Multi-store model of memory STM LTM Low Capacity Channel Sensory buffers

Sensory memory 4 Function –temporary input buffer between input sensors and perceptual process 4 Representation –direct copy of stimulus 4 Capacity/duration –very limited (0.25 to 2 seconds) –highly volatile, easily overwritten by new stimuli 4 Interface implications? –effectively none

Short term memory 4 Function –temporary working/output store –from sensory memory/cognitive process 4 Representation –transforms original stimulus to coded form (techniques for memory enhancement rely on improved coding) 4 Capacity –very limited (“seven plus or minus two units”) where a unit is an abstraction 4 Duration –short (less than 20 secs.) –must be continuously refeshed by rehearsal

STM - interface implications 4 Layout of screens –limit amount of information user has to retain avoid splitting logically related information provide memory extenders like multiple windows 4 Design of input –easy encoding few memory units needed; easier rehearsal short “sayable” codes, meaninful keywords 4 Response time provision –minimise retention time to avoid disrupting closures

Long term memory 4 Function –permanent store of what an individual has “learned” –poorly understood 4 Representation –semantic patterns - each individual stores information according to their own individual interpretation patterns –memorising is acquiring suitable patterns; remembering is correct retrieval of patterns 4 Capacity –effectively unlimited 4 Duration –unlimited, but degraded by confusion between old schema /new info. and vice versa

LTM - interface implications 4 Facilitate “learning” –creation and organisation of meaningful images mnemonic codes, iconic cues, real world metaphors etc. 4 Consistency –within and with other systems consistent screen template, common commands etc. –with related tasks 4 Emphasise “recognition” rather than “recall” –e.g., direct manipulation rather than command strings

Closure 4 Concerned with human grouping activity into meaningful “chunks” 4 Closure 4 Closure experienced at the end of each “chunk” –brain senses achievement and seeks rest! 4 Sense of closure increases with significance of “chunk” 4 Requires retention of all necessary info. in STM –disruption within closure degrades performance, increases error etc. 4 Size of chunks increase with experience/familiarity –novice views single UNIX command elements; expert sees whole scripts