Subjective Usability, Mental Workload Assessments and Their Impact on Objective Human Performance

Self-reporting procedures and inspection methods have been largely employed in the fields of interaction and web-design for assessing the usability of interfaces. However, there seems to be a propensity to ignore features related to end-users or the context of application during the usability assessment procedure. This research proposes the adoption of the construct of mental workload as an additional aid to inform interaction and web-design. A user-study has been performed in the context of human-web interaction. The main objective was to explore the relationship between the perception of usability of the interfaces of three popular web-sites and the mental workload imposed on end-users by a set of typical tasks executed over them. Usability scores computed employing the System Usability Scale were compared and related to the mental workload scores obtained employing the NASA Task Load Index and the Workload Profile self-reporting assessment procedures. Findings advise that perception of usability and subjective assessment of mental workload are two independent, not fully overlapping constructs. They measure two different aspects of the human-system interaction. This distinction enabled the demonstration of how these two constructs cab be jointly employed to better explain objective performance of end-users, a dimension of user experience, and informing interaction and web-design

The Importance of Human Mental Workload in Web Design

The focus of this study is the introduction of the construct of Human Mental Workload (HMW) in Web design, aimed at supporting current interaction design practices. An experiment has been conducted using the original Wikipedia and Google web-interfaces, and using two slightly different versions. Three subjective psychological mental workload assessment techniques (NASA-TLX, Workload Profile and SWAT) with a well-established assessments usability tool (SUS) have been adopted. T-tests have been performed to study the statistical significance of the original and modified web-pages, in terms of workload required by typical tasks and perceived usability. Preliminary results show that, in one ideal case, increments of usability correspond to decrements of generated workload, confirming the negative impact of the structural changes on the interface. In another case, changes are significant in terms of usability but not in terms of generated workloads, thus raising research questions and underlying the importance of Human Mental Workload in Interaction Design

Experienced metal workload, perception of usability, their interaction and impact on task performance

Past research in HCI has generated a number of procedures for assessing the usability of interacting systems. In these procedures there is a tendency to omit characteristics of the users, aspects of the context and peculiarities of the tasks. Building a cohesive model that incorporates these features is not obvious. A construct greatly invoked in Human Factors is human Mental Workload. Its assessment is fundamental for predicting human performance. Despite the several uses of Usability and Mental Workload, not much has been done to explore their relationship. This empirical research focused on I) the investigation of such a relationship and II) the investigation of the impact of the two constructs on human performance. A user study was carried out with participants executing a set of information-seeking tasks over three popular web-sites. A deep correlation analysis of usability and mental workload, by task, by user and by classes of objective task performance was done (I). A number of Supervised Machine Learning techniques based upon different learning strategy were employed for building models aimed at predicting classes of task performance (II). Findings strongly suggests that usability and mental workload are two non overlapping constructs and they can be jointly employed to greatly improve the prediction of human performance

Using fNIRS in usability testing: understanding the effect of web form layout on mental workload

Amongst the many tasks in our lives, we encounter web forms on a regular basis, whether they are mundane like registering for a website, or complex and important like tax returns. There are many aspects of Usability, but one concern for user interfaces is to reduce mental workload and error rates. Whilst most assessment of mental workload is subjective and retrospective reporting by users, we examine the potential of functional Near Infrared Spectroscopy (fNIRS) as a tool for objectively and concurrently measuring mental workload during usability testing. We use this technology to evaluate the design of three different form layouts for a car insurance claim process, and show that a form divided into subforms increases mental workload, contrary to our expectations. We conclude that fNIRS is highly suitable for objectively examining mental workload during usability testing, and will therefore be able to provide more detailed insight than summative retrospective assessments. Further, for the fNIRS community, we show that the technology can easily move beyond typical psychology tasks, and be used for more natural study tasks

Controller workload, airspace capacity and future systems.

In air traffic control (ATC), controller workload – or controller mental workload – is an extremely important topic. There have been many research studies, reports and reviews on workload (as it will be referred to here). Indeed, the joke is that researchers will produce ‘reviews of reviews’ (Stein, 1998). The present document necessarily has something of that flavour, and does review many of the ‘breakthrough’ research results, but there is a concentration on some specific questions about workload

Using fNIRS in usability testing: understanding the effect of web form layout on mental workload

Amongst the many tasks in our lives, we encounter web forms on a regular basis, whether they are mundane like registering for a website, or complex and important like tax returns. There are many aspects of Usability, but one concern for user interfaces is to reduce mental workload and error rates. Whilst most assessment of mental workload is subjective and retrospective reporting by users, we examine the potential of functional Near Infrared Spectroscopy (fNIRS) as a tool for objectively and concurrently measuring mental workload during usability testing. We use this technology to evaluate the design of three different form layouts for a car insurance claim process, and show that a form divided into subforms increases mental workload, contrary to our expectations. We conclude that fNIRS is highly suitable for objectively examining mental workload during usability testing, and will therefore be able to provide more detailed insight than summative retrospective assessments. Further, for the fNIRS community, we show that the technology can easily move beyond typical psychology tasks, and be used for more natural study tasks

Evaluating the Effectiveness of the Gestalt Principles of Perceptual Observation for Virtual Reality User Interface Design

There is a lot of interest and excitement surrounding the areas of Virtual Reality and Head-Mounted Displays with the recent releases of devices such as the Oculus Rift, Sony PSVR and the HTC Vive. While much of the focus for these devices has been related to sectors of the entertainment industries, namely the cinema and video game industries, there are many more practical applications for these technologies, with potential benefits in educational, training/simulation, therapeutic and modelling/design software. Developing a set of reliable guidelines for Virtual Reality User Interface Design could play a crucial role in whether the medium successfully integrates into the mass market. The Gestalt Principles of Perceptual Organisation offer a psychological explanation of human perception, with particular reference to pattern recognition and how we subconsciously group entities together. There are seven Principles of Perceptual Organisation, nearly all of which are currently widely used in User Interface design, offering designers guidelines on what the size, shape, position and colour the different components of an interface should be. This study presents an analysis on the effects that the employment of the Gestalt Principles has on the usability and mental workloads of Virtual Reality applications

Integration of an adaptive infotainment system in a vehicle and validation in real driving scenarios

More services, functionalities, and interfaces are increasingly being incorporated into current vehicles and may overload the driver capacity to perform primary driving tasks adequately. For this reason, a strategy for easing driver interaction with the infotainment system must be defined, and a good balance between road safety and driver experience must also be achieved. An adaptive Human Machine Interface (HMI) that manages the presentation of information and restricts drivers’ interaction in accordance with the driving complexity was designed and evaluated. For this purpose, the driving complexity value employed as a reference was computed by a predictive model, and the adaptive interface was designed following a set of proposed HMI principles. The system was validated performing acceptance and usability tests in real driving scenarios. Results showed the system performs well in real driving scenarios. Also, positive feedbacks were received from participants endorsing the benefits of integrating this kind of system as regards driving experience and road safety.Postprint (published version

Formalising Human Mental Workload as Non-Montonic Concept for Adaptive and Personalised Web-Design

Web Design has been evolving with Web-based systems becoming more complex and structured due to the delivery of personalised information adapted to end-users. Although information presented can be useful and well formatted, people have little mental workload available for dealing with unusable systems. Subjective mental workload assessments tools are usually adopted to measure the impact of Web-tasks upon end-users thanks to their ease of use and are aimed at supporting design practices. The Nasa Task Load Index subjective procedure has been taken as a reference technique for measuring mental workload, but it has a background in aircraft cockpits, supervisory and process control environments. We argue that the tool is not fully appropriate for dealing with Web-information tasks, characterised by a wide spectrum of contexts of use, cognitive factors and individual user differences such as skill, background, emotional state and motivation. Furthermore, in this model, inputs are averaged without considering their mutual interactions and relations. We propose to see human mental workload as non-monotonic concept and to model it via argumentation theory. The evaluation strategy includes coparisons with the NASA-TLX in terms of statistical correlation, sensitivity, diagnosticity, selectivity and reliability