Experiment 1 : Motivating Conversational Contributions Through Group Homogeneity and Individual Uniqueness

Under-contribution is a problem for many online communities. Social psychology theories of social loafing and goal-setting can lead to mid-level design goals to address this problem. We tested design principles derived from these theories in four field experiments involving members of an online movie recommender community. In each of the experiments participated were given different explanations for the value of their contributions. As predicted by theory, individuals contributed when they were reminded of their uniqueness and when they were given specific and challenging goals. However, other predictions were disconfirmed. For example, in one experiment, participants given group goals contributed more than those given individual goals. The article ends with suggestions and challenges for mining design implications from social science theories. Motivating Contributions in Online Communities Since at least 1979, when the first Usenet news sharing programs were created, online communities have co-evolved with the growth in computer networking. Today, 26 years later, people share news, information, jokes, music, discussion, pictures, and social support in hundreds of thousands of online communities. People benefit from the presence and activity of others in online communities—from the information and other resources they provide and the conversations they participate in. Using Social Psychology to Motivate Contributions to Online Communities: http://jcmc.indiana. edu/vol10/issue4/ling.html 1 of 30 13/1/2010 4:31 AM Despite the vibrancy of online communities, large numbers of them fail. In many online groups, participation drops to zero. Butler (1999) found that 50% of social, hobby, and work mailing lists had no traffic over a period of four months. On the popular peer-to-peer music sharing service, Gnutella, 10% of users provide 87% of all the music (Adar & Huberman, 2000). In open-source development communities, 4% of members account for 50% of answers on a user-to-user help site (Lakhani & Hippel, 2003), and 4% of developers contribute 88% of new code and 66% of code fixes (Mockus, Fielding, & Andersen, 2002). Although not everyone needs to contribute for a group to be successful (Nonnecke & Preece, 2000), groups with a large proportion of non-contributors may have difficulty providing needed services to members. We believe that it is an important and difficult challenge to design technical features of online communities and seed their social practices in a way that generates ongoing contributions from a larger fraction of the participants. In this article, we address the problem of under-contribution in an online community called MovieLens (Cosley, Lam, Albert, Konstan, & Riedl, 2003). MovieLens is a web-based movie recommender site where members rate movies, write movie reviews, and receive recommendations for movies. More than 20% of the movies listed in the system have so few ratings that the recommender algorithms cannot make accurate predictions about whether subscribers will like them. We describe interventions designed to boost contributions both to conversations about movies and ratings of them. Social science theories have helped computer-supported cooperative work (CSCW) designers and developers make sense of failures and focus attention on difficulties that will need to be overcome in system design (e.g., Grudin, 1989; Markus, 1987). Other CSCW researchers have drawn design inspiration and design guidelines from social science findings (e.g., Dourish & Bly, 1992; Erickson & Kellog, 2000; Preece, 2000). Our aim is to build an even stronger link between social science theories and CSCW design. First, we aim to draw on behavioral theories that explain why people do things rather than just on empirical regularities (or stylized facts). By drawing upon theory, designers can craft mechanisms to engage the causal mechanisms even in settings that on the surface appear quite different from settings where the stylized facts were observed. Second, we seek to implement alternative designs for which the theories predict different outcomes, so that results from field experiments can test the underlying theories or resolve questions on which the theories were silent. Motivating contributions, especially contributions to the communal good, is a topic that has received substantial attention in many branches of the social sciences. Economists and political scientists have observed that across a wide range of settings, people contribute less than the optimal amount of public goods and consume more than their fair share of common pool resources, although the antisocial behavior is considerably less than theories based on pure short-term self-interest would predict (see Ledyard, 1995 for a review). Social psychologists have identified an analogous phenomenon called social loafing. People exert less effort on a collective task than they do on a comparable individual task (see Karau & Williams, 1993 for a review). Karau and Williams (2001) developed the collective effort model to explain social loafing. In this article, we describe several attempts to mine the collective effort model and other theories from social psychology on the motivators of individual effort. We apply these principles to the design of appeals for soliciting contributions to MovieLens. In each of four experiments, we first identified the abstract mental states that the theories propose should lead to contribution, such as believing that one's contributions are unique in a group or that they Using Social Psychology to Motivate Contributions to Online Communities: http://jcmc.indiana. edu/vol10/issue4/ling.html 2 of 30 13/1/2010 4:31 AM will benefit the group. We then translated them into specific mental states that a participant in the MovieLens community might have, such as believing that he or she rates movies that few others rate or that their ratings help others. Next, we designed persuasive messages or other manipulations that we hoped would induce these mental states. We then conducted controlled randomized experiments by exposing existing MovieLens subscribers to these different manipulations. Three of the four experiments have been reported previously (Beenen et al., 2004; Ludford, Cosley, Frankowski, & Terveen, 2004). This article analyzes more comprehensively and rigorously the impact of the different manipulations on contribution behavior, especially movie ratings. Experiment 1: Motivating Conversational Contributions Through Group Homogeneity and Individual Uniqueness Social loafing, or free riding, is the robust phenomenon that occurs when people work less hard to achieve some goal when they think they are working jointly with others than when they think they are working by themselves. Karau and Williams' (1993) collective-effort model is a type of utility theory that claims that people work hard when they think their effort will help them achieve outcomes they value. Working in a group can influence how hard people work because it can change their perception of the importance of their contribution to achieving a specified level of performance, their likelihood of reaching the goal, and the value they place on the outcomes they gain by their efforts (Harkins & Petty, 1982; Kerr, 1983; Kerr & Bruun, 1983). (See Karau & Williams, 2001, and Figure 1 for a fuller description of the collective effort model.) The collective effort model identifies conditions under which people will socially loaf less. These include, among others: (a) believing that their effort is important to the group's performance, (b) believing that their contributions to the group are identifiable, and (c) liking the group they are working with. Both in laboratory settings (e.g., Harkins & Petty, 1982; Kerr, 1983; Kerr & Bruun, 1983) and online (Markey, 2000), social psychologists have tested the collective effort model by manipulating individuals' perceptions of the elements in Figure 1. Figure 1. The collective-effort model (adapted from Karau & Williams, 1993) We attempted to apply the insights from the collective effort model to the problem of under-contribution in MovieLens. MovieLens (http://movielens.umn.edu/login) is a movie recommender system that recommends to subscribers movies that they would enjoy, based on movie evaluations from other Using Social Psychology to Motivate Contributions to Online Communities: http://jcmc.indiana. edu/vol10/issue4/ling.html 3 of 30 13/1/2010 4:31 AM subscribers with similar tastes. In Experiment 1, we expanded MovieLens' functionality by adding new online discussion groups. The goal of the experiment was to identify ways of organizing the discussion groups so that people would offer conversational posts in the group and subsequently rate more movies in MovieLens. In Experiment 1 we tested predictions from the collective effort model which stated that people will contribute more to a group when they think their contributions are likely to be unique and when they like the group more. More details about this experiment are available in Ludford et al. (2004). Uniqueness of contribution The collective effort model posits that people will socially loaf less and contribute to a group more, the more they see their contribution as important to the group (Karau & Williams, 1993). If they believe that their contributions are redundant with those that others in the group can provide, then there is little reason to contribute, because their contributions have little likelihood of influencing the group. Conversely, if they think they are unique, they should be more motivated to contribute, because their contributions are more likely to influence the group. In Experiment 1, we manipulated subjects' perceived uniqueness by reminding them of movies they had seen but that others in the group had not. Hypothesis 1: People will contribute more to online communities when given personalized information showing that their contributions would be unique. S