Mental Models Sonia Chiasson and Robert Biddle Human Oriented Technology Lab Carleton University, Ottawa

Mental models 1943 Craik  humans translate external events into internal models used for reasoning

Mental models 1943 Young  mental model is users’ mental representation of their interaction with complex devices 1981

Mental models 1943 Norman  designer – system – user

Mental models 1943 Bayman & Mayer  user conception of the “invisible” info processing between input and output

Mental models 1943 Johnson-Laird  mental models are a method of representing knowledge and the manipulation of models is a form of reasoning

user’s mental model system image the actual system researcher’s conceptualization designer’s conceptual model Mental models according to Norman

What kinds of mental models can we encourage?

Metaphors shield users from tech details more accessible to novice users –framed as something relevant and meaningful –draws upon existing knowledge may have unintended consequences –users may draw unexpected/undesirable conclusions

EID approach Ecological Interface Design foster mental model that reflects actual system hierarchy of detail helps users diagnose/troubleshoot unexpected situations, understand impact of actions assumes knowledgeable user Overview... progressively more detail... Physical components and sensors

Current security interfaces Novices: –very limited models of computer security threats –magical computer *stuff* happens –UI does not foster useful mental models –invisibility/transparency is bad but common approach –“more education” = unrealistic burden on users –dangerous errors = personally at risk Experts: –domain knowledge –UI re-purposed/adopted for security purposes –multiple alarm, indicators, & visualizations –> must assimilate to make decision = often overwhelming –dangerous errors = system- wide vulnerabilities

As researchers/designers... we must consider... at least 3 topics

1. How to foster security mental models UI must convey info needed to accurately/easily predict and understand consequences of actions and system behaviour should we go with metaphor or EID approach? –what are the risks of each? –if we go with metaphors, is there an overarching “security” metaphor that could work? what is computer security like that would be relevant to non-technical users? –is it dependent target users?

2. Attacks on mental models how can attackers manipulate user mental models to their advantage? how can we defend against it? –can we ever provide cues that can’t be spoofed? does fostering a legitimate user’s mental model reveal info to attackers? how do we tell legit people what’s really happening without compromising security?

3. How to identify mental models how do we identify mental models? how can we tell if the appropriate model is being conveyed?

Wrap up different approaches to fostering mental models –metaphor vs EID current systems do poor job of conveying mental model for both novice and expert users must consider: –how to foster security mental models –how attackers take advantage of mental models –how to accurately identify user mental models