Visual aesthetics and user experience: a multiple-session experiment

The article reports a longitudinal lab experiment, in which the influence of product aesthetics and inherent product usability was examined over a period of 7 weeks. Using a 2 × 2 × 7 mixed design, visual aesthetics (high vs. low) and usability (high vs. low) were manipulated as between-subjects variables whereas exposure time was used as a repeated-measures variable. One hundred and ten participants took part in the study, during which they carried out typical tasks of operating a fully automated coffee machine. We measured user experience by using the following outcome variables: perceived usability, perceived attractiveness, performance, affect, workload and perceived coffee quality (gustatory aesthetics). We found no effect of visual aesthetics on user experience (including perceived usability as the chief outcome variable), which is in contrast to a considerable number of previous studies. The absence of such an effect might be associated with influencing factors that have not yet been given sufficient attention (e.g., user identification with product, sensory dominance, characteristics of specific products)

Questionnaire experience and the hybrid System Usability Scale: Using a novel concept to evaluate a new instrument

This article presents the concept of questionnaire experience (QX), intending to add a new element to the psychometric evaluation of questionnaires, which may eventually help increase the validity and reliability of instruments. The application of QX is demonstrated in the development of the Hybrid System Usability Scale (H-SUS), making use of items comprising pictorial and verbal elements to measure perceived usability. The H-SUS was modelled on the verbal version of the System Usability Scale (SUS). Since previous research showed advantages of pictorial scales over verbal scales (e.g., higher respondent motivation) but also disadvantages (e.g., longer completion times), we assumed that hybrid scales would combine the advantages of both scale types. The goal of this study was to compare the two instruments by assessing traditional psychometric criteria (convergent, divergent and criterion-related validity, reliability and sensitivity) and respondent-related aspects of QX (respondent workload, respondent motivation, questionnaire preference, and questionnaire completion time). An online experiment was carried out (N = 152), in which participants interacted with a smartphone prototype and subsequently completed the verbal SUS together with the H-SUS. Results indicate good psychometric properties of the H-SUS. Compared to the SUS, the H-SUS showed similar workload levels for questionnaire completion, higher levels of respondent motivation, but longer questionnaire completion time. Overall, the H-SUS is considered a promising alternative for the evaluation of perceived usability. Finally, QX can be considered a useful concept for identifying potential problems of psychometric instruments in a respondent-centred way, which may help improve the quality of future scales

The Influence of Product Aesthetics and Usability over the Course of Time: A Longitudinal Field Experiment

A longitudinal field experiment was carried out over a period of two weeks to examine the influence of product aesthetics and inherent product usability. A 2 x 2 x 3 mixed design was used in the study, with product aesthetics (high / low) and usability (high / low) being manipulated as between-subjects variables and exposure time as a repeated-measures variable (3 levels). A sample of 60 mobile phone users was tested during a multiple-session usability test. A range of outcome variables was measured, including performance, perceived usability, perceived aesthetics, and emotion. A major finding was that the positive effect of an aesthetically appealing product on perceived usability, reported in many previous studies, began to wane with increasing exposure time. The data provided similar evidence for emotion, which also showed changes as a function of exposure time. The study has methodological implications for the future design of usability tests, notably suggesting the need for longitudinal approaches in usability research

Social stress in human-machine systems: opportunities and challenges of an experimental research approach

This article presents some deliberations on methodological approaches to researching the effects of work-related social stress on performance, with particular consideration being given to machine-induced social stress. The article proposes a broad methodological approach to examine such effects. A particular focus is placed on performance after-effects (e.g. unscheduled probe tasks), extra-role behaviour, and task management behaviour because of conventional performance measures (i.e. scheduled tasks) often being unimpaired by social stressors. The role of the ‘performance protection mode’ as an important concept is discussed. A distinction is made between three facets of after-effects: performance-related, behavioural, and emotional. Unscheduled probe tasks and voluntary tasks are proposed to measure performance-related and behavioural after-effects. Propositions for specific experimental scenarios are made, allowing for sufficiently realistic simulations of social stress at work. The availability of such lab-based simulations of work environments offers good opportunities for this line of experimental research, which is expected to gain in importance since highly automated systems may modify the impact of human-induced social stress or may even represent a social stressor themselves. Finally, the considerations presented in this article are not only of relevance to the domain of social stress but to experimental stress research in general

Expertise, Automation and Trust in X-Ray Screening of Cabin Baggage

X-ray screening of passenger baggage is a key component in aviation security. The current study investigated how experts and novices performed in an X-ray baggage screening task while being assisted by an adaptable diagnostic aid. Furthermore, it examined how both groups operated and trusted this automated system. 30 experts (certified screeners) and 31 novices (students) had to indicate whether a target item (either a knife or a gun) was present in a series of X-ray images of cabin baggage. Half of the participants could choose between three different support levels of the diagnostic aid (DA): (1) no support, (2) a cue indicating the presence of a potential target without locating it, or (3) a cue indicating the presence of a potential target by surrounding it with a red frame. As expected, experts achieved higher detection performance (d’), were more self-confident and felt more competent in achieving the task than novices. Furthermore, experts experienced less time pressure and fatigue. Although both groups used the DA in a comparable way (in terms of support level used and frequency of level switches), results showed a performance increase for novices working with the DA compared to novices without support. This benefit of DA was not observed for experts. Interestingly, despite no difference in perceived trust ratings, experts were more compliant (i.e., following DA recommendations when it indicated the presence of a target) and reliant (i.e., following DA recommendations when it indicated the absence of a target) than novices. Altogether, the results of the present study suggested that novices benefited more from a DA than experts. Furthermore, compliance and reliance on DA seemed to depend on expertise with the task. Since experts should be better at assessing the reliability of the DA than novices, they may have used the DA as ‘back-up’ to confirm their decisions based on expertise (confirmatory function), while novices may have used it as a guide to base their decisions on (support function). Finally, trust towards a DA was associated with the degree to which participants found the DA useful

Click-correlative light and electron microscopy (click-AT-CLEM) for imaging and tracking azido-functionalized sphingolipids in bacteria

Sphingolipids, including ceramides, are a diverse group of structurally related lipids composed of a sphingoid base backbone coupled to a fatty acid side chain and modified terminal hydroxyl group. Recently, it has been shown that sphingolipids show antimicrobial activity against a broad range of pathogenic microorganisms. The antimicrobial mechanism, however, remains so far elusive. Here, we introduce 'click-AT-CLEM', a labeling technique for correlated light and electron microscopy (CLEM) based on the super-resolution array tomography (srAT) approach and bio-orthogonal click chemistry for imaging of azido-tagged sphingolipids to directly visualize their interaction with the model Gram-negative bacterium Neisseria meningitidis at subcellular level. We observed ultrastructural damage of bacteria and disruption of the bacterial outer membrane induced by two azido-modified sphingolipids by scanning electron microscopy and transmission electron microscopy. Click-AT-CLEM imaging and mass spectrometry clearly revealed efficient incorporation of azido-tagged sphingolipids into the outer membrane of Gram-negative bacteria as underlying cause of their antimicrobial activity