15. Human-Computer Interaction
THE TROUBLE WITH COMPUTERS AND SOFTWARE DESIGN
SOFTWARE DESIGN CYCLE: UNDERSTAND, DESIGN, AND EVALUATE
UNDERSTAND SYSTEM AND USER CHARACTERISTICS
Functionality -- creeping featurism Balance between functionality and ease of use Frequency of use Mandatory vs. discretionary use knowledge level of the user
DESIGN USING THEORIES AND MODELS
Foley and van Dam (1990) Conceptual level Semantic level Provides a mental model Semantic level Meaning/desired function Syntactic level How the semantic command is formed Lexical level Sequence of actions
Seven Stages of Action (Norman, 1986) Figure 15.2 Bridging the gulf of execution and gulf of evaluation
Models of User Performance for Design: GOMS Card, Moran, & Newell (1983) Model Human Processor
Keystroke Level Model (KLM) GOMS Six execution phase operators Physical motor: K – keystroking 0.28 P – pointing 1.1 H – homing 0.4 B – press mouse button 0.1 Mental M – mental preparation 1.35 System R – response Times are empirically determined Texecute = Tk + Tp + Th + Tb+ Tm+ Tr
Models of User Performance for Design: GOMS Design A: drag the file into the trash can[29] Design B: use the short cut “control + T”[30] method encoding (operator sequence)[31] method encoding (operator sequence)[32] initiate the deletion (M) find the file icon (M) point to file icon (P) press and hold mouse button (B) drag file icon to trash can icon (P) release mouse button (B) point to original window (P) find the icon for the to-be-deleted file (M) press mouse button (B) move hand to keyboard (H) press control key (K) press T key (K) move hand back to mouse (H) Total time 3P + 2B + 2M = 3*1.1 sec + 2*.1 sec+ 2*1.35 sec = 6.2 sec P + 2B + 2H + 2K + 2M = 1.1 sec + 2*.1 sec + 2*.4 sec + 2*.2 sec + 2*1.35 sec = 5.2 sec
DESIGN TO SUPPORT MENTAL MODELS WITH CONCEPTUAL MODELS AND METAPHORS
Making invisible parts and processes visible to the user Providing feedback Building in consistency Presenting functionality through a familiar metaphor
DESIGN USING PRINCIPLES AND GUIDELINES
General Usability Guidelines
Basic Screen Design Dialog Style Menus Fill-in forms Question-answer Command language Function keys Direct manipulation Natural language
DESIGN OF USER SUPPORT
EVALUATE WITH USABILITY HEURISTICS
EVALUATE WITH USABILITY TESTS AND METRICS
Prototypes Usability Metrics
Number of Users and Data Interpretation
Pitfalls of Usability Testing
INFORMATION TECHNOLOGY
Hypertext, Hypermedia, and the Internet Information Database Access Mediated retrieval Intelligent agents Spatially organized database Virtual and Augmented Reality Affective Computing