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This paper investigates the interplay among human cognitive processing differences (field dependence vs. field independence), alternative interaction device types (desktop vs. touch) and user authentication schemes (textual vs. graphical) towards task completion efficiency and effectiveness. A four-month user study (N=164) was performed under the light of the field dependence-independence theory which underpins human cognitive differences in visual perceptiveness as well as differences in handling contextual information in a holistic or analytic manner. Quantitative and qualitative analysis of results revealed that field independent (FI) users outperformed field dependent users (FD) in graphical authentication, FIs authenticated similarly well on desktop computers as on touch devices, while touch devices negatively affected textual password entry performance of FDs. Users' feedback from a poststudy survey further showed that FD users had memorability issues with graphical authentication and perceived the added difficulty when interacting with textual passwords on touch devices, in contrast to FI users that did not have significant usability and memorability issues on both authentication and interaction device types. Findings highlight the necessity to improve current approaches of knowledge-based user authentication research by incorporating human cognitive factors in both design and run-time. Such an approach is also proposed in this paper.

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Abstract. Challenges today in the Web personalization and adaptation research area are ranging not only to the heterogeneous user needs and user environment issues such as current location and time, but also on a number of other considerations with respect to multi-channel delivery of the applications concerning Web-based content related to services, educational multimedia, entertainment, commerce etc. Nowadays, most Web personalization systems implement various techniques to extract the user profiles, which serves as the main component of such systems, and based on given user preferences, navigation behaviour and the Web-based content returns the requested personalized result. The main scope of this paper is to present the various techniques employed by such systems with regards to user profiles extraction and introduce a comprehensive user profile, which includes User Perceptual Preference Characteristics. It further analyzes the main intrinsic users' characteristics like visual, cognitive, and emotional processing parameters incorporated as well as the "traditional" user profile characteristics that together tend to give the most optimized, adapted and personalized outcome. It finally presents a Web adaptation and personalization system that implements the proposed comprehensive user profile as well as initial evaluation results. IntroductionSince 1994, the Internet has emerged as a fundamental information and communication medium that has generated extensive enthusiasm. The Internet has been adopted by the mass market much quicker than any other technology over the past century and is currently providing an electronic connection between progressive businesses and millions of customers and potential customers whose age, education, occupation, interest, and income demographics are excellent for sales. The explosive growth in the size and use of the WWW as well as the complicated nature of most Web structures result in orientation difficulties, as users often lose sight of the goal of their inquiry, look for stimulating rather than informative material, or even use the navigational features unwisely. As the e-Services sector is rapidly evolving, the need for such Web structures that satisfy the heterogeneous needs of its users is becoming more and more evident. To alleviate such navigational difficulties, researchers have put huge amounts of effort to identify the peculiarities of each user group and analyze and design methodologies and systems that could deliver up-to-date adaptive and personalized information, with regards to products or services. To date, there has not been a concrete definition of personalization. The many adaptive hypermedia and Web personalization solutions offering personalisation features meet an abstract common goal: to provide users with what they want or need without expecting them to ask for it explicitly [1]. Further consideration and analysis of parameters and contexts such as users' intellectuality, mental capabilities, socio-psychological factors, emotional states and attention ...