1 Cognitive Modeling offers Explanations for Effects found in Usability Studies. Sabine Prezenski Nele Russwinkel Dep. of cognitive Modeling in dynamic HMS, TU Berlin Marchstr. 23, 10587 Berlin, Germany sabine.prezenski@tu-berlin.de ABSTRACT Two studies evaluate the usability of two versions of an android shopping list application. ACT-R modeling approaches and empirical findings are presented. It is shown that semantic networks have a strong influence on performance and learning. Effects of version updates are discussed. Author Keywords Usability; cognitive modeling; ACT-R; application; mobile; semantic network ACM Classification Keywords User centered design; ergonomics; theory and methods design tools and techniques; human factors; human Information processing; experimental design INTRODUCTION These days, life without mobile applications and smart phones is hard to imagine. The market for applications is growing rapidly [1]. For an application to be successful, high usability is compulsory. Conventional usability testing is time and money consuming. We therefore ask, how can usability of applications be guaranteed without testing costs exploding? The following paper argues that cognitive modeling with ACT-R can serve as substitute for extensive usability testing. We will present results of two studies of an application to show how learning in applications proceeds, why semantic knowledge is important and also focus on version updates effects. COGNITIVE MODELING & ACT-R Cognitive architectures such as ACT-R [2] offer a computable platform that represents well established theories about human information processing. With cognitive architectures it is possible to simulate cognitive mechanisms and structures such as visual perception or memory retrieval. ACT-R is a hybrid architecture, which means that is has symbolic (knowledge representations such as chunks and rules called productions) and sub symbolic components (activation of chunks and utility of productions). The structure of chunks is characterized by different slots (or attributes), that can be filled with information. Category membership is represented in slots; this allows building semantic networks. Furthermore, new chunks can be learned during a task. The production system persists of rules defined by an “if” and “then” part. If the cognitive system with its modules and chunks in the buffers meet the conditions of the rule it can be selected. Then the action part is executed. USABILITY Standard ISO 9241-11 defines usability as effectiveness, efficiency and satisfaction. General ergonomic principles for the design of dialogues between humans and information system are specified in Standard ISO-9241- 110, seven criteria are outlined (suitability for the task, suitability for learning, suitability for individualization, conformity with user expectations, self descriptiveness, controllability, and error tolerance). Most usability criteria however can be assessed with quantitative user tests. Suitability for learning can be measured via comparison of several runs [3]. It is commonly agreed, that human knowledge is represented in form of a semantic network [4]. Within these net categories, associations with subcategories and retrieval of subcategories succeed best and faster when the category representations are addressed. To answer the question, what is the best design for a menu structure, we have designed two versions of an application. One version has two subcategories (memory-like, Version A) with the disadvantages of more required clicks; the other has only one level of sub-categories (Version B) and therefore requires fewer clicks. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Permissions@acm.org. ECCE '14, September 01 - 03, 2014, Vienna, Austria © 2014 ACM. ISBN 978-1-4503-2874-6/14/09…$15.00 DOI: http://dx.doi.org/10.1145/2637248.2743001 Sabine Prezenski and Nele Russwinkel. 2014. Cognitive Modeling offers Explanations for Effects found in Usability Studies. In Proceedings of the 2014 European Conference on Cognitive Ergonomics (ECCE '14). ACM, New York, NY, USA, Article 36 , 4 pages. This is a post-print authors version. The original publication is available at the ACM Digital Library via DOI=http://dx.doi.org/10.1145/2637248.2743001