Marilyn Hughes Blackmon

A Comprehension-based Model of Web Navigation and Its Application to Web Usability Analysis

CoLiDeS, a comprehension-based cognitive model of Web navigation, offers a theoretical explanation of the impasses users often encounter during information search and retrieval from the W W W, and also identifies the determinants of success cases. In this model, acting on a single Web page screen object is regarded as the outcome of a multi-step process: parsing the current display containing up to about 200 screen objects into five to ten top-level schematic objects; focusing on one of these top-level schematic objects; comprehending and elaborating the screen objects within the focused-on area; and then selecting one of the actual screen objects as the target for the next action, the object whose representation bears the highest degree of semantic similarity to the user’s goal.

Tool for accurately predicting website navigation problems, non-problems, problem severity, and effectiveness of repairs

The Cognitive Walkthrough for the Web (CWW) is a partially automated usability evaluation method for identifying and repairing website navigation problems. Building on five earlier experiments [3,4], we first conducted two new experiments to create a sufficiently large dataset for multiple regression analysis. Then we devised automatable problem-identification rules and used multiple regression analysis on that large dataset to develop a new CWW formula for accurately predicting problem severity. We then conducted a third experiment to test the prediction formula and refined CWW against an independent dataset, resulting in full cross-validation of the formula. We conclude that CWW has high psychological validity, because CWW gives us (a) accurate measures of problem severity, (b) high success rates for repairs of identified problems (c) high hit rates and low false alarms for identifying problems, and (d) high rates of correct rejections and low rates of misses for identifying non-problems.

CogTool-Explorer: a model of goal-directed user exploration that considers information layout

CogTool-Explorer 1.2 (CTE1.2) predicts novice exploration behavior and how it varies with different user-interface (UI) layouts. CTE1.2 improves upon previous models of information foraging by adding a model of hierarchical visual search to guide foraging behavior. Built within CogTool so it is easy to represent UI layouts, run the model, and present results, CTE1.2s vision is to assess many design ideas at the storyboard stage before implementation and without the cost of running human participants. This paper evaluates CTE1.2 predictions against observed human behavior on 108 tasks (36 tasks on 3 distinct website layouts). CTE1.2s predictions accounted for 63-82% of the variance in the percentage of participants succeeding on each task, the number of clicks to success, and the percentage of participants succeeding without error. We demonstrate how these predictions can be used to identify areas of the UI in need of redesign.

Information scent determines attention allocation and link selection among multiple information patches on a webpage

This paper draws from cognitive psychology and cognitive neuroscience to develop a preliminary similarity-choice theory of how people allocate attention among information patches on webpages while completing search tasks in complex informational websites. Study 1 applied stepwise multiple regression to a large dataset and showed that success rate for web navigation tasks approaches 100% if a single information patch is highly similar in meaning to the user goal, and success rate falls dramatically if two or more information patches compete for the users attention and if only one contains a link that leads to accomplishing the search goal. Study 2 (n = 82) manipulated the independent variables task difficulty and website design and found statistically significant differences in success rate for both main effects and the interaction. Study 2 also found that the distribution of attention among available information patches was strongly determined by the rank ordering of semantic similarity between user goal and information patch but was not influenced by website designs with very different visual layouts. While these results offer verification of a similarity-choice theory of attention to information patches, caution is warranted in generalising too broadly from these results.

Rapid Theory Prototyping: An Example of an Aviation Task

We present our experience using CogTool, a tool originally designed for ease of use and learning by non-psychologist design practitioners, as a means for rapid theory exploration. We created seven iterations of a “model prototype” of an aviation task where each iteration produced errors that pointed to additional theory or device knowledge that should be incorporated to prevent those errors. This theory and knowledge was put into the next iteration by modifying the mock-up of the device, not by changing the implementation of the underlying cognitive model. This trick allowed us to rapidly change theory and knowledge and understand what must eventually migrate to the underlying cognitive model to provide general support for predictions of novice behavior in multi-step procedures with complex devices.

Applying psychology to design better human-machine systems: Crucial goals for cognitive task analysts.

A completed cognitive task analysis (CTA) describes theskills and conceptual knowledge necessary to competently/expertly perform complex jobs/tasks, such as piloting a commercial aircraft. The primary motivation for doing a CTA is to improve the performance of human-machine systems by developing better training programs, developing tests to certify job competence, improving teamwork, and/or designing computer systems to support human workers.