Chapter 2 Human Information Processing
HCI as a system human computer
Cognitive process
Human information processing
STUDYING HUMAN INFORMATION PROCESSES
Signal detection theory Cognitive model: encoding + decision Evaluation metrics: hit rate false alarm rate (during World War II, British radar observers detected fewer of the enemy’s radar signals after 30 minutes in a radar observation shift)
Reaction Time (RT) series of discrete processing stages Subtractive method selection of tasks that differ by a single stage e.g. compare the time to find a target link on two web pages that are identical except for the number of links displayed
Reaction Time (RT) series of discrete processing stages Additive factors method two variables that affect different stages should have additive effects on RT while two variables that affect the same stage should have interactive effects on RT e.g. mode of icon array (menu or dialog box), number of icons, and difficulty of movement had additive effects on response times
RT vs. accuracy
Neuroergonomics electroencephalograms (EEG) fMRI
INFORMATION PROCESSING IN CHOICE REACTION TASKS
Mental rotation R R
Response Selection RIGHT LEFT Hick-Hyman law (N equally likely alternatives): Compatibility effects verbal-vocal, spatial-manual Simon-effect: RIGHT LEFT red Stroop-effect blue green yellow
Response Execution Fitt’s low: D is distance to the target (b is different at various devices) W is target width other factors, e.g. point-click vs. point-drag
PROBLEM SOLVING AND DECISION MAKING
Problem solving New tasks are frequent at computers problem space representation initial and goal states, operations heuristic path-finding naive vs. expert
Mental model based on interaction, the user develops a representation of how the system is functioning for a given task metaphors real life (e.g. desktop) other tasks/systems (e.g. web browsers) human decision-making heuristics (when the outcome associated with a choice is uncertain) e.g. anchoring heuristic involves making a judgment regarding probabilities of alternative states based on initial information
HUMAN MEMORY IN INFORMATION PROCESSING
Memory Memory refers to explicit recollection of information in the absence of the original stimulus and to persisting effects of that information on information processing that may be implicit. Episodic vs Semantic memory Declarative vs procedural sensory stores, short-term memory (working memory), and long-term memory
short-term memory (STM) limited capacity several seconds 7 ± 2 memory spans HCI: distraction (18 sec) STM load at complex HCI tasks
short-term memory, STM
long-term memory, LTM shallow vs deep/semantic processing pl. searching for a link on a webpage generation effect e.g. passwords mnemonic techniques (ryhme, loci) false memories
ATTENTION IN INFORMATION PROCESSING
Attention Attention is increased awareness directed at a particular event or action to select it for increased processing. result in enhanced understanding of the event, improved performance of an action, or better memory for the event allows to filter out unnecessary information
Attention models What happens with unattended stimuli? filter-attenuation theory early selection by filtering attenuated signal may be sufficient late-selection theory stimuli are identified and later ignored load theory When memory load is high, it is not possible to suppress irrelevant information at a cognitive level
Attention and HCI multi-task, different modality change blindness attentional blink visual search menu/icon feature integration theory attention demands decrease as a task is practiced
Other cognitive areas in HCI Task loading and stress Emotions, mood, sentiment Motivation and influencing …
Summary Cognitive models of human information processing HCI can be effective if it is compatible with human information processing