Social influence is key in technology adoption, but its role in security-feature adoption is unique and remains unclear. Here, we analyzed how three Facebook security features' Login Approvals, Login Notifications, and Trusted Contacts-diffused through the social networks of 1.5 million people. Our results suggest that social influence affects one's likelihood to adopt a security feature, but its effect varies based on the observability of the feature, the current feature adoption rate among a potential adopter's friends, and the number of distinct social circles from which those feature-adopting friends originate. Curiously, there may be a threshold higher than which having more security feature adopting friends predicts for higher adoption likelihood, but below which having more feature-adopting friends predicts for lower adoption likelihood. Furthermore, the magnitude of this threshold is modulated by the attributes of a feature-features that are more noticeable (Login Approvals, Trusted Contacts) have lower thresholds.

One of the largest outstanding problems in computer security is the need for higher awareness and use of available security tools. One promising but largely unexplored approach is to use social proof: by showing people that their friends use security features, they may be more inclined to explore those features, too. To explore the efficacy of this approach, we showed 50,000 people who use Facebook one of 8 security announcements'7 variations of social proof and 1 non-social control-to increase the exploration and adoption of three security features: Login Notifications, Login Approvals, and Trusted Contacts. Our results indicated that simply showing people the number of their friends that used security features was most effective, and drove 37% more viewers to explore the promoted security features compared to the non-social announcement (thus, raising awareness). In turn, as social announcements drove more people to explore security features, more people who saw social announcements adopted those features, too. However, among those who explored the promoted features, there was no difference in the adoption rate of those who viewed a social versus a non-social announcement. In a follow up survey, we confirmed that the social announcements raised viewer's awareness of available security features.

In this paper we study large-scale emotional contagion through an examination of Facebook status updates. After a user makes a status update with emotional content, their friends are significantly more likely to make a valence-consistent post. This effect is significant even three days later, and even after controlling for prior emotion expressions by both users and their friends. This indicates not only that emotional contagion is possible via text-only communication and that emotions flow through social networks, but also that emotion spreads via indirect communications media.

I analyze the use of emotion words for approximately 100 million Facebook users since September of 2007. "Gross national happiness" is operationalized as a standardized difference between the use of positive and negative words, aggregated across days, and present a graph of this metric. I begin to validate this metric by showing that positive and negative word use in status updates covaries with self-reported satisfaction with life (convergent validity), and also note that the graph shows peaks and valleys on days that are culturally and emotionally significant (face validity). I discuss the development and computation of this metric, argue that this metric and graph serves as a representation of the overall emotional health of the nation, and discuss the importance of tracking such metrics.

The Internet has become a place of refuge for individuals with autism spectrum disorders (ASD). In particular, weblogs are a popular option for personal expression via the Internet. Perhaps this means of communication is well suited to bypassing deficits in social interaction and communication that characterize ASD. Using the Linguistic Inquiry and Word Count (LIWC) dictionaries [10], we compared blogs of individuals with ASD to the writing of neurotypical (NT) bloggers. We found that rates of word usage were nearly identical in the two groups with one exception - there was more variation in the use of social words in ASD compared to NT blogs. This similarity in language between ASD and NT authors suggests that communication deficits routinely found in people with ASD may be due to the social context in which their communication skills are tested, and that the affordances of asynchronous computer-mediated communication may offer alternative means of testing and expression.

We present a large-scale analysis of the content of weblogs dating back to the release of the Blogger program in 1999. Over one million blogs were analyzed from their conception through June 2006. These data was submitted to the Text Analysis: Word Counts program [12], which conducted a word-count analysis using Linguistic Inquiry and Word Counts (LIWC) dictionaries [20] to provide and analyze a representative sample of blogger word usage. Covariation among LIWC dictionaries suggests that blogs vary along five psychologically relevant linguistic dimensions: Melancholy, Socialness, Ranting, Metaphysicality, and Work-Relatedness. These variables and others were subjected to a cluster analysis in an attempt to extract natural usage groups to inform design of blogging systems, the results of which were mixed.

We propose a method of measuring people's sense of presence in computer-mediated communication (CMC) systems) based on linguistic features of their dialogues. We create variations in presence by asking participants to collaborate on physical tasks in four CMC conditions. We then correlate self-reported feelings of presence with the use of specific linguistic features. Regression analyses show that 30% of the variance in self-reported presence can be accounted for by a small number of task-independent linguistic features. Even better prediction can be obtained when self-reported coordination is added to the regression equation. We conclude that linguistic measures of presence have value for studies of CMC.

This article considers tools to support remote gesture in video systems being used to complete collaborative physical tasks-tasks in which two or more individuals work together manipulating three-dimensional objects in the real world. We first discuss the process of conversational grounding during collaborative physical tasks, particularly the role of two types of gestures in the grounding process: pointing gestures, which are used to refer to task objects and locations, and representational gestures, which are used to represent the form of task objects and the nature of actions to be used with those objects. We then consider ways in which both pointing and representational gestures can be instantiated in systems for remote collaboration on physical tasks. We present the results of two studies that use a "surrogate" approach to remote gesture, in which images are intended to express the meaning of gestures through visible embodiments, rather than direct views of the hands. In Study 1, we compare performance with a cursor-based pointing device that allows remote partners to point to objects in a video feed of the work area to performance side-by-side or with the video system alone. In Study 2, we compare performance with two variations of a pen-based drawing tool that allows for both pointing and representational gestures to performance with video alone. The results suggest that simple surrogate gesture tools can be used to convey gestures from remote sites, but that the tools need to be able to convey representational as well as pointing gestures to be effective. The results further suggest that an automatic erasure function, in which drawings disappear a few seconds after they were created, is more beneficial for collaboration than tools requiring manual erasure. We conclude with a discussion of the theoretical and practical implications of the results, as well as several areas for future research.