In addition, people play video games in competitive or cooperative modes, and this deeply affects the game experience (Peng & Hsieh, 2012 ). Playing competitively increases enjoyment (Schmierbach, Xu, Oeldorf‐Hirsch, & Dardis, 2012 ), and committed gamers are more motivated to play competitively (Jansz & Martens, 2005 ). Additionally, playing exergames competitively provided positive experiences to competitive study participants but it had detrimental effects for less competitive participants (Song, Kim, Tenzek, & Lee, 2013 ). However, previous research has not documented whether playing against a normal weight or obese computer‐controlled opponent agent influences physical activity while playing an exergame. We rely on social comparison mechanisms (Festinger, 1954) to study how avatar and opponent agents' body size affect physical activity outcomes in exergames. From this perspective, we assume that one's avatar is the salient target of comparison, that opponent characters are the comparison standard when playing video games, and that such social comparison should impact players' concurrent physical activity. Though Peña and Kim ( 2014 ) propose that social comparison theory explains the effects of avatar and opponent character appearance, this is only an hypothesized theoretical relationship as they did not provide empirical evidence that participants compared the physical traits of their avatar against the physical traits of their virtual opponent. Thus, this study explores how perceived body‐size differences between avatars and virtual opponents statistically moderates physical activity outcomes, and also examines the interaction effects of using normal weight or obese avatars playing against normal weight or obese opponent characters.

In particular, the Proteus effect has not been thoroughly tested in the context of playing exergames. For instance, does avatar appearance affect people's concomitant physical activity while playing an exergame? In a recent study, female participants operating normal weight avatars showed increased physical activity relative to those using obese avatars (Peña & Kim, 2014 ). Female participants also showed increased physical activity when self and opponent avatars had normal weights , along with decreased physical activity when using a normal weight avatar playing against an obese opponent agent (Peña & Kim, 2014 ). Though these results are encouraging, studies have not documented whether these findings replicate in other populations, such as men playing exergames. Consider that women are more likely to internalize thin‐ideal images in the media (e.g., Hargreaves & Tiggemann, 2003; Levine & Murnen, 2009 ). Thus, it is possible that Peña and Kim's ( 2014 ) findings apply more strongly to women in comparison to men, and thus here we replicate their study with an all‐male sample.

One specific area of interest is whether embodiment manipulations (e.g., visual, auditory, and motion cues in the game) affect physical activity and other positive outcomes when playing exergames (Kim, Prestopnik, & Biocca, 2014 ). For instance, presence or the sense of “being there” in a virtual environment along with game enjoyment is connected to how embodiment manipulations influence exergame physical activity outcomes (Kim et al., 2014 ; Lombard & Ditton, 1997 ). Also, exergame players who created an avatar reflecting their ideal self reported higher perceived game interactivity than those who created an avatar mirroring their actual self (Jin, 2009 ). However, studies have not fully explored the basic mechanisms behind the behavioral effects of embodiment manipulations in exergames. For example, avatars are a digital body or visual cue that represents video game players, and embodiment manipulations such as avatar appearance set in motion self‐perception and priming effects that lead people operating avatars to think and behave in ways congruent with avatar appearance (i.e., the Proteus effect, Peña, Hancock, & Merola, 2009 ; Yee & Bailenson, 2007 ).

Exergames are video games that require the performance of physical gestures to control the game and, thus, allow users to exert themselves physically (e.g., dance, play tennis; Staiano & Calvert, 2011 ). There is rising interest in how video games can boost physical activity and other positive outcomes (Peng, Lin, & Crouse, 2011 ). For example, participants with high body‐image dissatisfaction reported similar or more favorable exergame experiences relative to those with low body‐image dissatisfaction (Song, Kim, & Lee, 2014 ). In addition, participants' social physique anxiety regarding how others may judge their appearance decreased during exergame play (Song et al., 2014 ).

Because proper social comparison processes take into account the target of comparison and the comparison standard (Mussweiler & Strack,), we also focus on the statistical moderation effects of avatar and opponent agent body size on physical activity outcomes. Though Peña and Kim () hypothesized such a link, their study did not provide evidence that participants were aware of and then compared virtual body‐size differences. The most efficient way to draw social comparisons is finding key features that are revealing of an opponent's abilities and then assess if we have those features, too (Mussweiler & Strack,). Tennis players are expected to be thin, agile, and fit (Harris & Foltz,), thus perceived body‐size differences between avatars and opponent characters should moderate physical activity outcomes. For example, participants that perceive a comparative body‐size disadvantage (i.e., upward social comparison), such as operating a more obese avatar in comparison to their virtual opponent's body size should show decreased physical activity. Thus:

In addition, downward social comparison should occur when using a normal weight avatar playing against an obese opponent. In this condition, participants will show decreased physical activity as those competing against a perceived inferior opponent may disregard their virtual rival and conserve energy. Consider that downward social comparison is linked to decreases in performance because achieving superiority from the outset can have demotivating effects (i.e., a complacency effect, Bandura & Jourden,). For example, participants that achieved superiority easily showed decreased job performance but higher self‐efficacy, thus implying that “complacent self‐assurance creates little incentive to expend the increased effort needed to attain high levels of performance.” (Bandura & Jourden,, p. 949). Thus:

Upward social comparison processes are linked to decreases in performance because a comparative decline in attainments can undermine effective self‐regulation and increase erratic thinking (Bandura & Jourden,). In a controlled experiment that manipulated social comparison perspective, participants that were in a disadvantageous position showed steeper declines in job performance, along with decreased perceived self‐efficacy or belief in their capabilities (Bandura & Jourden,). In the present context, upward social comparison effects should occur when using an obese avatar competing against a normal weight opponent character. If so, then:

Upward and downward social comparisons are two central collective processes. Upward social comparison refers to comparing oneself to someone who is perceived as more accomplished on a given dimension (e.g., a fit tennis player), while downward social comparison refers to comparing oneself to someone perceived as less skilled (Nabi & Keblusek, 2014 ). For example, exposure to thin‐ideal female full‐body and body part magazine ads led to increased negative mood and body dissatisfaction among women (Tiggemann & McGill, 2004 ). In addition, female viewers of cosmetic surgery programs engaging in upward social comparison to media figures showed increased approach‐oriented emotions, while viewers engaging in downward social comparisons showed more negative affect (Nabi & Keblusek, 2014 ). Also, participants that were more responsive to personal cues (i.e., reported feeling what their faces were expressing) were less satisfied with their weight and showed lower self‐esteem when exposed to thin model pictures compared to more obese pictures (Wilcox & Laird, 2000 ).

The influence of avatar body size in social comparisons should depend on its applicability and representativeness (Mussweiler & Strack, 1995 ). Accessible information about being good at tennis should have stronger effects than being good at soccer because tennis skills are more applicable. People also consider whether information is representative or appropriate to reach a judgment. Information about present tennis skills is more representative than older memories (Mussweiler & Strack, 1995 ). In the present context, we hypothesize that people will consider accessible and representative information, such as avatar appearance (i.e., salient target of comparison) and game opponent appearance (i.e., salient comparison standard).

Thus, this study complements the assumption that avatars and opponent agents activate concepts and stereotypes stored in memory (Peña, 2011 ) with the supposition that people use virtual characters' features to draw comparative judgments. On this regard, social comparison theory can inform how avatars and opponent agents affect physical activity in exergames. According to social comparison theory (Festinger, 1954), people are motivated to accurately compare and evaluate their abilities and opinions. In social comparisons, the self temporarily becomes the target of comparison, and the salient other (e.g., an opponent) becomes the comparison standard (Mussweiler & Strack, 1995 ).

Though exposure to concepts and stereotypes can prime subsequent behaviors, priming research has left several questions unanswered. For example, Bargh ( 2006 ) invited researchers to explain how primes occurring in parallel interact with each other, and which prime “wins” when conflicting responses are activated. People are often exposed to avatars and opponent agents in parallel because both characters may appear onscreen at the same time. For example, a tennis exergame may feature conflicting primes by having a normal weight avatar play against an obese agent, or vice versa.

Priming models assume a direct perception‐behavior link. “Perceiving is for doing” and, thus, activating a concept or behavior increases the tendency to engage in that behavior (Chartrand & Bargh, 1999 ). From this approach, perceptual inputs are translated automatically into behavioral outputs without the involvement of intention or conscious goals (Dijksterhuis & Bargh, 2000). Thus, activating social concepts through perception is neurologically similar to performing that behavior ( Dijksterhuis & Bargh, 2000). Consider that exposure to violent video game scenes decreases affective neural activity but increases cognitive neural activity, implying that exposure to virtual violence activates and inhibits specific brain processes (Weber, Ritterfeld, & Mathiak, 2006 ). In relation to perception directly translating into behavior, participants imitated nonverbal behaviors (e.g., smiling, foot shaking) when interacting with a confederate engaging in those behaviors compared to interacting with a confederate that did not engage in those behaviors in face‐to‐face contexts (Chartrand & Bargh, 1999 ).

Priming mechanisms are a chief alternative explanation to the Proteus effect (Peña, 2011 ). People's avatar activates learned concepts stored in memory, thus affecting cognition and behavior in line with such concepts (Peña et al., 2009 ). According to Peña ( 2011 ), avatar appearance operates through spreading activation mechanisms (Collins & Loftus, 1975 ). Social concepts are stored in memory in a semantic network of related information, and so activating a concept (e.g., “obese avatar”) triggers linked ideas (e.g., “sluggishness”). For example, people using avatars with aggressive connotations (e.g., avatars in black; avatars in KKK‐like robes) developed more aggressive attitudes and created more violent stories relative to those using nonaggressive avatars (e.g., avatars in white; avatars dressed as doctors, see Peña et al., 2009 ).

The influence of avatar appearance on users is known as the Proteus effect, and it is attributed to self‐perception theory (Yee & Bailenson, 2007 ). From this perspective, people operating avatars examine their own behavior in ways similar to an imaginary third party to explain what attitudes may have caused them (Yee & Bailenson, 2007 ). In support of this, participants operating more physically attractive avatars showed more confidence in a virtual setting by keeping shorter interpersonal distances and disclosing more information compared to those using less physically attractive avatars (Yee & Bailenson, 2007 ). Avatar appearance is also related to game performance in massively multiplayer online games, as tall attractive characters had the highest game levels whereas short attractive characters had the lowest game levels (Yee, Bailenson, & Duchenaut, 2009 ). In addition, female participants who controlled sexualized avatars reported more body‐related thoughts than those who controlled nonsexualized avatars, and participants who saw their own faces on sexualized avatars showed increased rape myth acceptance (Fox, Bailenson, & Tricase, 2013 ).

Participants were asked if they knew the purpose of the experiment and whether there was a connection between the different sections in the study. The questions used in the awareness check were adapted from Bargh and Chartrand's ( 2000 ) funneled debriefing technique. After reading the participants' responses, the authors determined that all of the participants remained unaware of how avatar and opponent character body size were hypothesized to affect physical activity. Participants thought the experiment was testing if they were in shape, personal body image, and how people perform when playing difficult video games.

Perceived avatar and opponent character body‐size scores were used to ensure that the body‐size manipulations affected participants' perceptions of the characters. Participants rated the normal weight avatar as thinner ( M = 2.98, SD = 1.21) than the obese avatar ( M = 4.23, SD = 1.44), F (1, 96) = 23.29, p < .001, η 2 = .20. In addition, participants perceived the normal weight opponent character to be thinner ( M = 3.23, SD = 1.31) than the obese opponent character ( M = 4.33, SD = 1.52), F (1, 96) = 14.54, p < .001, η 2 = .13. Overall, the virtual character body‐size manipulations were successful.

Participants were asked to separately indicate which silhouette drawing looked the most like their avatar and the opponent character using a set of nine drawings ranging from very thin to very obese bodies. This procedure was previously used by Fallon and Rozin (1985), who gave participants silhouette drawings to indicate which figure resembled their real figure and which looked like their ideal figure. The validity of this single item approach to indicate body image perceptions has been established in numerous previous studies using the same drawings (e.g., Cohn et al., 1993; Stunkard, Sorenson, & Schulsinger, 1980 ).

This factor was measured with ActiGraph accelerometers. After playing three matches, the accelerometers' data was saved on a computer. Mean wrist and mean waist physical activity counts (count min −1 ; total activity counts divided by the time for game play) were calculated for each participant. Mean wrist and waist activity were uncorrelated, r (94) = .008, ns and, thus, were analyzed separately. The data was suitable for parametric analysis (Skewness Wrist activity = .71, SE Wrist activity = .25; Skewness Waist activity = .77, SE Waist activity = .25; Kurtosis Wrist activity = .15, SE Wrist activity = .49; Kurtosis Waist activity = .25, SE Waist activity = .49).

Participants were recruited using the cover story that the researchers were pretesting materials for a future study to prevent participants from guessing the aim of the experiment. When the participants came to the laboratory, they were given informed consent forms and then randomly assigned to one of the four experimental conditions. Participants went through a training session with an experimenter to introduce the Nintendo Wii controls. When the participants expressed that they were comfortable playing the game, the researcher outfitted the participants with two accelerometers. One accelerometer was strapped around the participant's waist, and another accelerometer was strapped around their dominant hand's wrist. After participants were outfitted with accelerometers, the researcher presented a randomly assigned experimental avatar and an opponent agent on the TV screen. The researcher asked the participants to keep their eyes on the screen while both virtual characters were being displayed (Figure 1 ). This assured that participants could compare self and opponent character's body size. After this, the participants played three tennis matches against the opponent agent. The matches lasted between 10 and 15 minutes. The researcher noted the game scores after each match. At the end of the third match, the researcher collected the accelerometers and asked the participants to fill out a questionnaire. Each participant's weight and height were recorded and used to calculate their BMI. Participants were given an awareness check questionnaire that asked them whether they were suspicious of the manipulations in the experiment, and whether they were aware of the purpose of the study (see Awareness Check section). Finally, participants received a debriefing statement at the end of all questionnaires. Each experiment took a total of 40 minutes.

Two ActiGraph GT3X accelerometers were used to measure participants' physical activity while playing the game. The accelerometers collected activity counts or the summation of the absolute values measuring change in acceleration measured during specific time periods (ActiGraph, 2009 ). Higher activity counts imply more intense body movement during a time period. In the current study, body movement was measured at 15‐second time intervals to capture detailed changes in body movements accurately (Nilsson, Ekelund, Yngve, & Sjöström, 2002 ). Because upper‐body movements are required to play sports game on the Wii (Peng et al., 2011 ), the participants wore the accelerometers at two upper‐body locations (one on the wrist of the dominant hand and the other on the waist).

Participants were randomly assigned to a normal weight or obese avatar as well as normal weight or obese opponent agent conditions (see Figure 1 ). These characters were specially created for the study. The avatar and the opponent agent were essentially the same male virtual character. The only difference was that the avatar was controlled by human participants while the opponent agent was controlled by the Wii console. The body size of the avatar/agent was manipulated by setting a different BMI (BMI = kg/m 2 ) for the normal or obese virtual character. The normal weight character was thin and had a BMI of 18.6 (where normal range BMI is 18.5 to 24.9). The obese character had a BMI of 32.1 (where obese BMI ≥ 30.0). Other than body size, both characters were similar on all physical characteristics including face, clothes, date of birth, and height. The self and opponent avatars were Caucasian males and wore tennis clothes (Figure 1 ). To maintain consistency across the experimental conditions, audio volume, game location, and game difficulty level were kept equal.

The experiment was conducted using a Nintendo Wii. Individual participants played Virtua Tennis 2009 on a 50‐inch LCD TV. In the game, players can create customized avatars or choose an avatar from a roster of famous tennis players. Participants needed to hold the controller as a racket and move their body to play Virtua Tennis. The player's avatar and the opponent agent were visible onscreen.

The study was a 2 (avatar: normal weight vs. obese) by 2 (opponent agent: normal weight vs. obese) factorial between‐subjects experiment. The study employed an all‐male sample ( N = 96). The participants were students at a large West Coast public university in the U.S. Male participants were between 18 and 32 years old ( M = 21.25, SD = 2.35). Fifty‐one percent were Asian, 19.8 % were Hispanic, 17.7% were Caucasian, 3.1% African‐Americans, 2.1% Pacific Islanders, and 6.3% who reported belonging to other ethnicities. Participants had been using computers for a long time ( M = 11.07 years, SD = 3.44 years). Most participants used computers every day ( M = 6.95, SD = .27; where 1 = never, 7 = every day). Participants had been playing video games for about 10 years ( M = 9.91, SD = 4.88). 91.7% participants had played Nintendo Wii games in the past.

Overall, the results confirmed the effects reported above. Participants using the obese avatar showed reduced wrist activity compared to those that used the normal weight avatar ( b = ‐279.75, SE = 95.04, t (94) = ‐2.94, p = .004). As predicted, perceiving one's avatar as one standard deviation more obese than the opponent character was also a significant moderator that decreased wrist physical activity ( b = ‐340.58, SE = 131.44, t (94) = ‐2.59, p = .01). This finding confirmed H4 and is discussed below. In addition, mean perceived avatar and opponent agent body‐size difference was a significant moderator that decreased wrist physical activity ( b = ‐272.72, SE = 95.37, t (94) = ‐2.85, p = .005). This result was unexpected and is further discussed below.

H4 predicted that social comparisons between avatar vs. opponent agent body size would moderate the direct effect of avatar appearance on physical activity. To address this question, a model 1 moderation analysis was performed with PROCESS (Hayes, 2013 ). The full results of the analysis appear in Table 1 . In this model, avatar body size was the predictor variable and wrist activity was the outcome variable based on the results of H1. In the model, the difference between perceived avatar and opponent body‐size scores was employed as the moderator because this metric reflects the difference between the perceived body size of the virtual characters. To test for moderation effects, PROCESS created three values for the difference between perceived avatar and opponent body‐size scores based on the mean of this moderator variable +/‐1 standard deviation from the mean (Hayes, 2013 ). The ‐1 standard deviation moderator value was negative (‐1.57), and it represented participants perceiving their avatar as thinner than the opponent character. The +1 standard deviation moderator value was positive (1.27), and it denoted participants perceiving their avatar as more obese than the opponent character. In addition, the mean perceived avatar and opponent agent body‐size difference was negative and quite small (‐.15), indicating that on average, participants perceived the opponent agent to be just slightly more obese than their avatar.

The data was initially examined with a 2 (avatar: normal weight, obese) by 2 (opponent agent: normal weight, obese) ANCOVA. Male participants' BMI was entered as a covariate in order to control for the effect of participant body size. BMI was insignificant thus it was dropped from the analysis. The final analysis was carried out with a 2 (avatar: normal weight, obese) by 2 (opponent agent: normal weight, obese) ANOVA. H1 reasoned that male participants using normal weight avatars would show increased wrist and waist activity. Male participants assigned to the normal weight avatar showed more wrist activity ( M = 1364.73, SD = 513.27) than those assigned to the obese avatar ( M = 1095.26, SD = 340.60), F (1, 94) = 9.21, p = .003, partial η 2 = .09. However, avatar body size did not affect participants' waist activity, F < 1. Thus, H1 was partially supported. H2‐H3 were disconfirmed as there were no avatar/opponent agent interaction effects on participants' physical activity ( F wrist (1, 94) = 2.04, ns , and F waist < 1).

Discussion

This study tested perception‐behavior assumptions by examining how avatar body size affected participants' concurrent physical activity while playing an exergame. The study also investigated social comparison effects by examining how opponent character body size influenced participants' physical activity outcomes. We also attempted to document possible gender differences regarding how virtual characters' body size affected physical activity outcomes by replicating with an all‐male sample a previous study that had an all‐female sample.

Overall, participants using normal weight avatars showed higher wrist activity in comparison to those operating obese avatars. This finding expands on the Proteus effect by showing how avatar appearance influenced physical activity outcomes among men playing exergames. Consider that exergames require users to use motion controllers to interact with the game, while previous studies had examined the Proteus effects using desktop computers and virtual reality systems (Peña et al., 2009; Yee & Bailenson, 2007). In particular, this finding is congruent with the perception‐behavior link, which states that perceiving a person, stereotype, or behavior increases people's tendency to behave similarly oneself (Chartrand & Bargh, 1999).

Additionally, perceived avatar and opponent character body‐size differences moderated the direct effect of avatar body size on wrist activity at high avatar/opponent character body‐size difference. In particular, perceiving the avatar as more obese than the opponent character was a significant moderator that decreased wrist physical activity. It is possible that participants felt at a disadvantage and thus showed decreased wrist physical activity when their avatar was perceived as more obese than their opponent. This finding confirmed the predictions of social comparison theory, particularly in regards to upward social comparisons. Upward social comparison refers to comparing oneself with someone perceived as more accomplished (Nabi & Keblusek, 2014). From this standpoint, participants may have estimated that they lacked the features of skilled tennis players when using a more obese avatar in comparison to a virtual opponent of a normal body size, and thus displayed less physical effort because they were discouraged by the comparison (e.g., Bandura & Jourden, 1991). Future studies should continue investigating how upward social comparisons affect player performance. Though previous studies have documented that users' cognition and behavior is affected by avatar appearance (i.e., the Proteus effect, Peña et al., 2009; Yee & Bailenson, 2007), the present results imply that social outcomes in exergames are affected by the appearance of one's virtual self in conjunction with the appearance of virtual others (see also Peña & Kim, 2014). This is a critical theoretical distinction that has not been sufficiently explored as there are few studies documenting the effects of parallel exposure to conflicting primes (i.e., normal or obese virtual characters, see Bargh, 2006). Perhaps the most important contribution of this study is broadening the palette of theories that explain social outcomes in exergames. While the Proteus effect explains behavioral effects at the individual level (i.e., avatar appearance affects the behavior of people operating avatars), social comparison processes can moderate the influence of the Proteus effect when people play exergames competitively with other virtual characters. Overall, behavioral outcomes in exergames may not only stem from the appearance and attributes implied by one's virtual character (the Proteus effect) but are also regulated by how we perceive our avatar in comparison to other characters (social comparison processes).

In addition to the moderation effects described above, perceived avatar and opponent character body‐size differences also moderated the direct effect of avatar body size on wrist activity at average avatar/opponent character body‐size difference. On average, participants perceived the opponent character to be slightly more obese than their avatar, and such difference moderated and decreased wrist physical activity. This moderation effect was not predicted, but it may imply a downward social comparison effect in that participants showed less physical effort when their opponent was just slightly more overweight in comparison to their avatar. Downward social comparisons refer to comparing oneself to someone perceived as less proficient (Nabi & Keblusek, 2014). In other words, participants using normal weight avatars may have exerted less wrist activity because they disregarded their obese virtual opponent. This effect is congruent with how downward social comparison may increase complacency and decrease performance (Bandura & Jourden, 1991). This study contributes to the literature by documenting how perceived avatar and opponent agent body‐size differences moderated wrist physical activity based on downward social comparison mechanisms. This improves on previous studies that had hypothesized such a theoretical relationship but did not provide empirical evidence that participants compared the physical traits of their avatar against the physical traits of their virtual opponent (see Peña & Kim, 2014).

Though moderation effects were observed, there were no statistical interaction effects of avatar and opponent character body size on physical activity outcomes among male participants. However, Peña and Kim (2014) observed such effects among female participants as female participants showed increased physical activity when both avatar and opponent character had a normal weight. Additionally, female participants had decreased physical activity when using a normal weight avatar playing against an obese opponent character. This difference is perhaps connected to social comparisons among women and men entailing different motivational processes. In the US and the Netherlands, women were more likely to engage in social comparisons relative to men (Gibbons & Buunk, 1999). Women were also more likely to internalize thin‐ideal images in the media (Levine & Murnen, 2009). For example, female TV audience members exposed to thin models showed more motivation to be thin and less body satisfaction (Harrison & Cantor, 1997). Finally, women comparing themselves to fashion magazine ads featuring thin and attractive models showed more positive reactions when comparing themselves on the basis of intelligence than when engaging in physical appearance comparisons (Tiggemann & Polivy, 2010). By replicating Peña and Kim's (2014) study, we can conclude that male participants were less responsive to social comparison effects when playing with normal or obese avatars and opponent characters, and that this is congruent with studies showing stronger social comparison processes among women as a result of exposure to media information linked to physical appearance.

Overall, why was perceived body‐size difference a significant moderator but the expected interaction effects were insignificant? This is especially puzzling when considering that the expected moderation and interaction effects were equivalent to each other. For example, reduced physical activity when using obese avatars playing against normal weight virtual opponents was not confirmed as an interaction effect (H2) but received support as a moderator when using the perceived body size difference measure (H4). Though this may seemingly be a limitation of our social comparison assumptions, one possibility is that the explicit and implicit nature of these predictions influenced the results. H4 relied on participants being explicitly asked to rate their avatar and virtual opponent's body size, while H2 was tested as an implicit effect based on mere exposure to the avatars. It is possible that the implicit or explicit nature of social comparisons may underlie why the overt measure was a significant moderator but a similar prediction that was tested more implicitly was not. Note that Peña and Kim (2014) confirmed a similar prediction with an all‐female sample. Considering the present results, one avenue for future research is examining whether women are influenced by implicit virtual social comparisons (e.g., mere exposure to normal weight and obese avatars and opponents), while men show similar effects only when explicitly comparing avatars and opponents.

Limitations and Future Research This research had several limitations. First, avatar body size affected male participants' wrist activity but, in Peña and Kim's (2014) study, avatar body size manipulations affected female participants' waist activity. One explanation to this discrepancy is that male and female participants reacted differently to the exergame task. When aggregating and comparing the two samples, female participants showed increased physical activity while playing the exergame (M Wrist Females = 1835.07, SD Wrist Females = 493.70; M Waist Females = 263.44, SD Waist Females = 103.30) compared to male participants (M Wrist Males = 1229.99, SD Wrist Males = 453.91; M Waist Males = 157.42, SD Waist Males = 69.23), F Wrist (1, 188) = 76.52, p < .001, partialη2 = .29, and F Waist (1, 188) = 68.34, p < .001, partial η2 = .27. This implies that female participants moved around more while playing the game. However, according to the experimenters' notes, male participants remained more static but hit the virtual tennis ball harder with the controller instead of moving around more. Future studies should examine how gender affects the way in which players approach exergames (e.g., overall movement vs. forcefulness of specific movements). Second, game camera positioning might have affected the results. The avatar was positioned up close to the player on the screen and the opponent agent was positioned farther away on the other end of the tennis court and appeared to be smaller on the screen by default. Though this may be perceived as a limitation, game camera positioning was consistent across all conditions. Thus, if there was error induced by the game camera's position, then such error was a constant across all conditions. In addition, camera positioning had the benefit of allowing players to be exposed to both characters. Third, the study did not account for how using avatars of the same weight as the participant could influence physical movement. For instance, avatars that physically resemble the user can be more persuasive (Fox et al., 2013). This is important given that there is a range of customization options in the Virtua Tennis game. Future research should examine the effects of virtual characters that have the same weight as the user. Finally, the effect sizes of the manipulations were small. These effects nonetheless matter given that the manipulation of the independent variable (avatar and opponent agent body size) was minimal and did not raise participants' awareness, whereas the dependent variable (physical activity) is difficult to influence given the range of factors that determine physical activity. For example, motivations to engage in physical activity include appearance concerns, increasing strength and endurance, stress management, weight management, and increasing health and/or avoiding illness (Kilpatrick, Hebert, & Bartholomew, 2005). Indeed, extrinsic factors such as the appearance of virtual characters in exergames had not been previously connected to physical activity outcomes (see Kilpatrick et al., 2005). Also of importance, given the vast scale of people's exposure to video games, even small effects can have large aggregated consequences. Consider that 59% of Americans play video games (Entertainment Software Association, 2014), and that repeated exposure to video game content should reinforce specific cognitive, emotional, and behavioral patterns on gamers given time (Anderson, Gentile, & Dill, 2012). In addition, the documented link between avatar appearance manipulations and cognitive and behavioral outcomes (i.e., the Proteus effect) reinforces the importance of these findings for public health, especially when considering that the present results replicated a previous study (Peña & Kim, 2014).