Over 60% of U.S. households now have a personal computer (Gaither, 2002; Kraut et al., 1998) and over 50% have Internet access (United States Department of Commerce, 2002). Despite the recent proliferation of services available online, Americans still use the Internet most for interpersonal communication (Horrigan & Rainie, 2001; Kraut, Mukhopadhyay, Szczypula, Kiesler & Scherlis, 1999; Nie, Hillygus & Erbring, 2002; Wellman, Quan Haase, Witte & Hampton, 2001). For example, 85% of those who used the Internet during a typical day in 2004 sent or received email (Pew Internet and American Life Project, 2002), far more than used any other single online application or information source. In addition to electronic mail, other Internet communication services are becoming increasingly popular—instant messaging, chat rooms, multi-user games, auctions, web logs, friendship networks, and participation in a myriad of online groups.
If communication dominates Internet use for a majority of its users, there is good reason to expect that the Internet will have a positive social impact, both in terms of its users' social integration in a network of family, friends and community and the benefits that flow from this integration. However, there is controversy in the research literature about whether use of the Internet increases or decreases users' social participation and the psychological and health benefits people generally receive from this participation. Some optimistic reports claim that using the Internet leads to the emergence of a new social circle (e.g., Kraut et al., 2002; Turkle, 1997) and the development of deep and long-lasting social relationships on-line (McKenna, Green & Gleason, 2002) and that it augments involvement in existing communities by providing new social spaces for communication (e.g., Katz & Aspden, 1997; Wellman et al., 2001). In contrast, other analyses suggest that frequent Internet use has negative social outcomes. In these studies, frequency of Internet use was associated with increases in depression and social isolation (Kraut et al., 1998) and declines in spending time with family and friends and in attending social events (Nie et al., 2002).
Most of the claims, both positive and negative, about the way Internet changes social participation are based on evidence from cross-sectional surveys, comparing individuals who have Internet access to those who do not have it, comparing heavier users of the Internet with lighter users, or comparing earlier adopters to later ones. One should not draw conclusions about causal relationships from this research. As Singer and Willet (2003) argue, “[t]o model change, you need longitudinal data that describe how each person in the sample changes over time. We begin with this apparent tautology because too many empirical researchers seem willing to leap from cross-sectional data that describe differences among individuals … to making generalizations about change over time (p. 9).” Applying this logic when reviewing the literature on the social impact of the Internet, Nie argues, “Internet users do not become more sociable; rather, they already display a higher degree of social connectivity and engagement, due to the fact that they are better educated, better off financially, and less likely to be among the elderly” (Nie, 2001).
Consequences of Using the Internet
One goal of this paper is to bring new data to bear on the question of how use of the Internet is changing social participation. Current research has shown conflicting evidence about the effects of the Internet on communication and social relationships. Several arguments have been advanced concerning the impact of Internet use on social involvement. One, dating back to early concerns of anti-social effects of Internet use, is that Internet use takes time away from positive social interactions thus having a negative effect on social relationships and psychological well-being (Kraut et al., 1998; Nie et al., 2002). This argument, dubbed the hydraulic or crowding-out effect of Internet use, had been supported by results by Nie and colleagues (Nie et al., 2002; Nie & Hillygus, 2002), showing that Internet users spent significantly less time interacting face-to-face with family and friends than non-users. Many writers have worried that the ease of Internet communication might encourage people to spend more time alone, talking online with strangers or forming superficial “drive by” relationships, at the expense of deeper discussion and companionship with existing friends and family (e.g., Putnam, 2000, p. 179). Given the constraints of a 24-hour day, the inefficiency of online communication may cause heavy users of the Internet to maintain under-developed social relationships with their online communication partners (e.g., Parks & Roberts, 1998) or to maintain a smaller stock of relationships. A further concern is that even when conversing with close friends and family, lower quality, online conversations might displace higher quality, face-to-face and telephone conversations (Cummings, Butler & Kraut, 2002). For example, the impoverished nature of online communication can cause people to omit the social niceties that promote or maintain social relationships (e.g., Brennan, 1991; Cummings et al., 2002; Sproull & Kiesler, 1991).
In contrast, other researchers have argued that Internet use has important positive social effects on individuals (McKenna et al., 2002; McKenna & Bargh, 2000), groups and organizations (Sproull & Kiesler, 1991), communities (e.g., Hampton & Wellman, 2001), and society at large (e.g., Hiltz & Turoff, 1978). Much of the research literature favors the proposal that Internet-based modes of communication augment existing modes of communication, providing more facets for social interaction and expanding our ability to communicate and keep in touch (Cole & Robinson, 2002; Katz & Rice, 2002; Kestnbaum, Robinson, Neustadtl & Alvarez, 2002). Robinson and his colleagues (Robinson, Kestnbaum, Neustadtl & Alvarez, 2000), for example, argue that Internet users actually spend more time socializing with family and friends when compared to non-users. They reported that compared to non-users, Internet users spent more time communicating face-to-face and over the phone and less time watching TV and sleeping. Because the Internet permits social contact across time, distance, and personal circumstances, it allows people to connect with distant as well as local family and friends, co-workers, business contacts, and strangers who share similar interests. Broad social access could increase people's social involvement, as the telephone did in an earlier time (e.g., Fischer, 1992).
Whether Internet use influences social participation and relationships is an important policy question. A long empirical research literature in psychology shows that social participation, including contact with neighbors, friends, and family, and participation in social groups, generally improves people's social support, their probability of having fulfilling personal relationships, their sense of meaning in life, their self-esteem, their commitment to social norms and to their communities, and their psychological and physical well-being (e.g., Cohen & Wills, 1985; Diener, Suh, Lucas & Smith, 1999; Thoits, 1983; Williams, Ware & Donald, 1981). Some researchers have suggested that Internet use might have different effects on social involvement depending on personality or base-line levels of social participation. For example, McKenna & Green (2002) proposed that introverts gain more socially from Internet use than do extroverts. They argued that anonymity and privacy in text-based communication provides shy and introverted individuals with a way to overcome difficulties in communication, thus compensating for difficulties fostered by personality (McKenna, 1999; McKenna & Bargh, 2000). Sproull and Kielser (1991) have suggested that distant or marginal members gain most by electronic participation in groups and organizations.
In an effort to look more closely at whether personality moderates the effects of Internet use on social involvement, Kraut et. al. (2002) examined extroversion, a stable personality characteristic associated itself with many forms of social interaction. They found that extroverts benefited more socially from higher levels of Internet use than did introverts. Few other studies, however, have collected personality measures along with measures of Internet use and social involvement, and so this result has not yet been replicated. One of the goals of the present research is to examine whether effects of Internet use on social involvement vary with extroversion.
To examine these issues, we describe the results of a national panel survey carried out in 2000 and 2001 by the Pew Internet & American Life Project (http://www.pewinternet.org/). This survey, developed jointly with the HomeNet project at Carnegie Mellon University (http://homenet.hcii.cs.cmu.edu/), collected data about Internet use and social participation from a national sample at two time periods. These data allow us to examine whether the use of the Internet changes such basic elements of social participation as the methods that people use to communicate with their social partners and the off-line social activities they engage in together. We also examine the impact of Internet use on respondents' perceptions of the social support they receive. Because introverts and extroverts may use the Internet differently and using the Internet may have different consequences for them, we will also examine whether this personality variable moderates any impact that Internet use has on social participation.
Although theory predicting the impact of the Internet on social participation has stressed its role as a communication tool, most studies have measured Internet use as whole, not distinguishing communication from other uses (Cole & Robinson, 2002;. Katz & Rice, 2002; Kraut et al., 2002; Kraut et al., 1998; Nie & Hillygus, 2002). At the base of both the “hydraulic” and the “augmentation” hypotheses is a supposition that communication over the internet will influence the amount or quality of communication using other modalities. The hydraulic hypothesis is that Internet communication substitutes for communication by telephone or in person, while the augmentation hypothesis is that Internet communication stimulates these other modes of communication. In the first part of this paper, we will examine the impact of Internet use as a whole on social participation. In the second part, we examine the extent to which the main Internet communication service — electronic mail — inhibits or stimulates communication by telephone and in person with particular social partners, and reciprocally, how these other communication modalities influence email use.
A Comparison of Survey Research Methods
The methodological goal of this paper is to illustrate how research design can influence the conclusions one can draw about the effects of Internet use. To do so, we contrast cross-sectional analyses and hierarchical linear growth models for each dependent variable collected at two time periods.
As discussed earlier, most claims about the social impact of Internet use are based on evidence from cross-sectional analyses. As Nie amd Hilligus (2002) note, pre-existing differences among heavy and light users may account for differences among them in social participation. It is well known, for example, that Internet users and non-users differ in demographics, attitudes, values, and other factors (see United States Department of Commerce, 2002 for evidence on demographic differences). Although some recent research suggests that the disparity between users and non-users is becoming smaller on some dimensions (United States Department of Commerce, 2002; Cummings & Kraut, 2002), important demographic differences still exist. For example, the online population is still younger, better educated and richer (Howard, Rainie & Jones, 2001). These are demographic characteristics that are also associated with social participation.
Researchers use multivariate regression techniques to attempt to control statistically for pre-existing differences among Internet users and non-users in cross-sectional samples. However, these statistical controls are invariably inadequate. Because of errors in measurement, statistical methods never completely remove the effects of demographic and other control variables included in the analyses. In addition, many relevant variables, such as extroversion and other relatively stable predispositions toward social behavior, are rarely measured and hence are unavailable for statistical control. As a result, associations between Internet use and social outcomes found in cross-sectional studies can be spurious, attributable to pre-existing differences in third variables that are associated with both Internet use and the social outcome. For example, Carroll and his colleagues (Carroll, Rosson, Kavanaugh, Dunlap, Schafer & Snook, in press) have shown that extroversion is associated with both Internet use and a variety of types of social behavior. As noted earlier, most cross-sectional research does not control for extroversion.
Even if it were feasible to demonstrate convincingly a non-spurious link between Internet use and social participation in cross-sectional data, it is impossible to establish the causal direction of such a link from data collected at a single point in time. Some researchers have used structural equation modeling to claim causal relationships based on cross-sectional data (e.g., LaRose, Eastin & Gregg, 2001). However, this technique does not test whether the modeler's assumptions about causal direction are correct.
Longitudinal analyses of panel data offer more solid ground for making causal claims. Panels consist of data collected multiple times from the same individuals. Very few studies have used panel data to examine the impact of Internet use, although they are becoming more frequent (e.g., Gershuny, 2002; Kraut et al., 2002; Kraut et al., 1998). Appropriate analysis of panel data examines the way a putative causal variable is associated with changes in a putative outcome. The hypothetical data plotted in Figure 1, showing the probability of heavy and light Internet users engaging in some social behavior at two times, illustrates the fundamental premise, that differences among groups at one time tell little about changes in the groups over time. In Figure 1A, heavy Internet users initially participate more than light users, and their participation grows faster than that of light users. In Figure 1B, heavier users participate more than light users in the first period, but they increase more slowly, so that by the second time period light users have surpassed them in social participation. In Figure 1C, the groups do not differ initially, but over time heavy Internet users increase their social participation while light users decrease theirs.
Figure 1. Hypothetical relationships between intial levels of social participation and changes in social participation depending upon levels of Internet use
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The ability to evaluate the same people over time significantly reduces at least one threat to causal inference—that pre-existing differences among individuals account for differences in the outcome variable. Because the same people are examined more than once, they bring the same demographic, personality and other cross-sectional differences to each data collection episode, effectively controlling for variation among individuals in both measured and unmeasured variables.
We acknowledge at the outset that longitudinal designs are not panaceas. They are still subject to validity threats. Other events co-varying with time may drive both changes in Internet use and changes in outcomes. These covariates can be internal to the individuals, such as learning or maturation, or external, such as the business cycle or change in popular culture. In addition, pre-existing differences among individuals may lead some of them to be more susceptible to change. Also, because of errors of measurement, pre-existing differences among participants are never fully statistically controlled in longitudinal designs. Only experimental research, in which participants are randomly forced to use the Internet or are prevented from using it, can lead to pure inferences about causation. However, true experiments are difficult to perform when one is seeking to examine broad social effects in the population or when examining the impact of technology on phenomena, such as the development of friendship, that are likely to emerge only after long periods of time. In addition, as Kraut et al. (2002) demonstrated, random assignment of participants to use the Internet may no longer be possible, at least in the United States among people who own a personal computer. In their study, over 80% of individuals randomly assigned to a non-Internet control group subscribed to Internet service on their own.
In the rest of this paper paper, we will first consider the question of the influence of overall Internet use on sociability in general, comparing results obtained from cross-sectional and longitudinal analyses. We will then focus on a particular relationship, investigating whether communicating in one modality with a selected individual changes communication with that partner in other modalities.