Designing computer-human interfaces for multiple-goal environments is challenging because people pursue multiple goals with conflicting priorities. Safety-critical environments, such as driving, aggravate the need for a more nuanced understanding of interfaces that may reconcile conflicting tasks. Speech interfaces are prime examples of such interfaces. In this article, we investigate how design variations of an in-vehicle speech interface influence performance of a primary task (driving safely) and a secondary task (e-mailing). In a controlled experiment, we test the performance implications of using single computer-generated Text-To-Speech (TTS) voice and multiple matching TTS voices while users respond to e-mails with varying levels of complexity during driving. Our results indicate that the number of voices used has a significant effect on both driving performance and handling e-mail--related activities. We discuss potentially unintended consequences of making the interface too naturalistic and too engaging for the driver and conclude with theoretical and practical implications.

Social connectedness is an indicator of the extent to which people can realize various network benefits and is therefore a source of social capital. Using the case of Twitter, a theoretical model of social connectedness based on the functional and structural characteristics of people's communication behavior within an online social network is developed and tested. The study investigates how social presence, social awareness, and social connectedness influence each other, and when and for whom the effects of social presence and social awareness are most strongly related to positive outcomes in social connectedness. Specifically, the study looks at the concurrent direct and moderating effect of two structural constructs characterizing people's online social network: network size and frequency of usage. The research model is tested using data (n = 121) collected from two sources: (a) an online survey of Twitter users and (b) their usage data collected directly from Twitter. Results indicate that social awareness, social presence, and usage frequency have a direct effect on social connectedness, whereas network size has a moderating effect. Social presence is found to partially mediate the relationship between social awareness and social connectedness. The findings of the analysis are used to outline design implications for online social networks from a human–computer interaction perspective.

This paper uses cognitive fit theory to analyze the problem solving process in spreadsheet analyses. Cognitive fit theory proposes the formation of mental representation as a part of the problem solving process. However, there is little research examining mental representation, which is a key concept in cognitive fit theory. This study examines the formation of mental representation and proposes an alternative mechanism of cognitive fit between different problem representations and their corresponding mental representations when the task is invariant, but the problem representation changes. Mental representation is then empirically assessed based on the application of Hick’s law, which states that the response time of users making a choice varies with the logarithm of the number of possible choices. Therefore, this study contributes to research on cognitive fit theory by proposing an alternative fit and by demonstrating a feasible approach for identifying mental representations. It contributes to spreadsheet research by showing how problem representations affect task performance in the case of spreadsheet error correction.