ARTICLE IN PRESS Journal of Experimental Social Psychology Journal of Experimental Social Psychology xxx (2004) xxx–xxx www.elsevier.com/locate/jesp How low can you go? Ostracism by a computer is suﬃcient to lower self-reported levels of belonging, control, self-esteem, and meaningful existenceq Lisa Zadro,a,* Kipling D. Williams,b,* and Rick Richardsona a School of Psychology, Faculty of Science, University of New South Wales, UNSW Sydney 2052, Australia b Department of Psychology, Macquarie University, Sydney, NSW 2109, Australia Received 20 June 2003; revised 22 October 2003 Abstract Previous research has demonstrated self-reports of lower levels of four fundamental needs as a result of short periods of face-toface ostracism, as well as short periods of Internet ostracism (Cyberball), even when the ostracizing others are unseen, unknown, and not-to-be met. In an attempt to reduce the ostracism experience to a level that would no longer be aversive, we (in Study 1) convinced participants that they were playing Cyberball against a computer, yet still found comparable negative impact compared to when the participants thought they were being ostracized by real others. In Study 2, we took this a step further, and additionally manipulated whether the participants were told the computer or humans were scripted (or told) what to do in the game. Once again, even after removing all remnants of sinister attributions, ostracism was similarly aversive. We interpret these results as strong evidence for a very primitive and automatic adaptive sensitivity to even the slightest hint of social exclusion. Ó 2004 Elsevier Inc. All rights reserved. Ostracism—the act of being excluded and ignored (Williams, 2001)—is ubiquitous. Reviewing the ethological, anthropological, and social psychological literature reveals that ostracism is used by many species, by children and adults, in primitive tribes and modern industrialized societies, as a formal method of reprimand among nations, institutions, and organizations and as an informal emergent reaction on playgrounds and hallways, with large groups, small groups, and dyads. Ostracism is also powerful. Studies have shown that people subjected to ostracism for a short period of time report worsened mood, anger, and lower levels of four state measures of needs proposed by Williams (1997, 2001) to be threatened by ostracism: belonging, control, q This research was funded by an Australian Research Council Grant to the second author, and comprised part of the ﬁrst authorÕs doctoral dissertation. We would like to extend our thanks to Bibb Latane for comments that initially triggered our interest in pursuing this line of inquiry, and Keith Lim and Trevor Case for their technical assistance. * Corresponding authors. E-mail addresses: firstname.lastname@example.org (L. Zadro), email@example.com. edu.au (K.D. Williams). 0022-1031/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jesp.2003.11.006 self-esteem, and meaningful existence. These studies consisted largely of a laboratory-based ball-tossing paradigm, in which participants partook in a spontaneous ball-toss game with two other confederate participants. When the other two individuals began tossing the ball just between themselves, ostracized participants slumped in their chairs, looking despondent, after only 4 min. Studies of long-term ostracism report incidences of attempted suicide and depression (Williams & Zadro, 2001), and even mass-shootings (Leary, Kowalski, Smith, & Phillips, 2003). Recently, Williams, Cheung, and Choi (2000) reported that individuals who played a virtual ball-toss game on the computer, ostensibly with others who were logged on to the website, also reported worsened mood and lower need levels. Additionally, if given the opportunity to make spatial judgments with a new group of individuals, ostracized participants were more likely to conform to this groupÕs unanimously incorrect answers. One goal of the Williams et al. (2000) research was to ﬁrst establish a baseline condition in which ostracism would have no eﬀects, and then to add on necessary ARTICLE IN PRESS 2 L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx factors until ostracism had a negative impact on the four needs. The authors were surprised to ﬁnd out that what they thought would be the baseline turned out to be suﬃciently adverse. One goal of the present studies, therefore, was to create conditions even less meaningful than those in the Williams et al. (2000) studies, in order to determine the necessary and suﬃcient conditions for ostracism to have an aversive impact. To the extent that such a baseline can be established, then we can gain a clearer idea what aspects of ostracism are essential. Study 1 In Study 1, participants were either ignored or included during Cyberball—a cyber analogue of a balltossing game (Williams et al., 2000, 2002)—by two other players whose identity was manipulated. Targets were told that they were playing Cyberball with either two computer-generated players or two human players prior to the start of the game. If the identity of the source is an important component in determining the aversiveness of ostracism, then targets who are ostracized by two human players should report lower levels of primary needs than targets who are ostracized by two computer-generated players or targets who are included in the game. If the identity of the source is not important—rather, the very act of ostracism is aversive enough to induce deleterious psychological eﬀects— then targets who are ostracized by humans or computers should both report lower levels of mood and of the four primary needs when compared to targets who are included in the game. Method Participants and design Eighty ﬁrst-year undergraduates enrolled in introductory psychology at the University of New South Wales were randomly assigned to a 2 (inclusionary status: ostracism vs. inclusion) 2 (attributed source: computer-generated players or human players) betweenS design. Participants volunteered to take part in the experiment in return for course credit. Eighteen participants were excluded because of technical diﬃculties with the computers and the Internet connection, thus the ﬁnal experiment consisted of 62 participants (20 males, 42 female, M age ¼ 19.9, SD ¼ 2:7). Procedure One participant per session arrived at the laboratory, and was seated in front of a computer.1 Participants were told that the study involved the eﬀects of mental 1 In both studies, cardiovascular measures were taken periodically, but only the self-report data are reported in the present paper. visualization, and that to assist them in practicing their skills at mental visualization they would be playing an Internet ball-toss game on the computer. They were told that performance in the game was unimportant, and instead, the game was merely a means for them to engage their mental visualization skills. They were asked to visualize the situation, themselves, and the other players. The game was accessed via the Internet (a downloadable version of this game is available at: http://www.psy.mq.edu.au/staﬀ/kip/Announce/cyberball). The game depicts three ball-tossers, the middle one representing the participant. The game is animated and shows the icon throwing a ball to one of the other two. When the ball was tossed to the participants, they were instructed to click on one of the other two icons to indicate their intended recipient, and the ball would move toward that icon. The game was set for 40 total throws (the game lasted approximately 6 min). Once the instructions were read, the participant clicked the ‘‘Next’’ link and the program randomly assigned them to one of the four conditions. At the end of the game, the website instructed participants to inform the experimenter that they had ﬁnished, and they were then instructed to ﬁll out a post-experiment questionnaire. Inclusion/ostracism manipulation. If assigned to the inclusion condition, participants received the ball for roughly one-third of the total throws. If assigned to the ostracism condition, participants received the ball twice at the beginning of the game, and for the remaining time, never received the ball again. Sources manipulation. Half the participants were told that they were playing with two other individuals who were stationed in similar laboratories at two other universities in Sydney. This cover story was augmented by staged phone calls to the other experimenters making sure that their participants were ready to go. The other half were told that they were playing the game with a computer. Dependent measures. The questionnaire contained several manipulation checks for inclusion/ostracism: ‘‘What percent of the throws were thrown to you?,’’ ‘‘To what extent were you included by the other participants during the game?,’’ and a 9-point bipolar scale (‘‘accepted/rejected’’). The questionnaire also contained a number of questions that asked participants to assess their levels of four needs that they felt during the game. These needs were: belonging (‘‘I felt poorly accepted by the other participants,’’ ‘‘I felt as though I had made a ‘‘connection’’ or bonded with one or more of the participants during the Cyberball game,’’ ‘‘I felt like an outsider during the Cyberball game’’), control (‘‘I felt that I was able to throw the ball as often as I wanted during the game,’’ ‘‘I felt somewhat frustrated during the Cyberball game,’’ ‘‘I felt in control during the Cyberball game’’), self-esteem (‘‘During the Cyberball game, I felt good about myself,’’ ‘‘I felt that the other ARTICLE IN PRESS L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx 3 Table 1 Means and standard deviations (in parentheses) of variables in Study 1 (all scales 1 ¼ not at all to 9 ¼ very much so, unless otherwise stated) Source Human Fundamental needsa Belonging (a ¼ :74) F ð1; 57Þ ¼ 34:99, p < :0005b Control (a ¼ :72) F ð1; 57Þ ¼ 32:5, p < :0005 Self-esteem (a ¼ :70) F ð1; 57Þ ¼ 11:1, p ¼ :002 Meaningful existence (a ¼ :66) F ð1; 58Þ ¼ 50:7, p < :0005 Moodc Ancillary variables I enjoyed playing the Cyberball game F ð1; 58Þ ¼ 10:2, p ¼ :002 I felt angry during the Cyberball game F ð1; 58Þ ¼ 8:2, p ¼ :006 Manipulation checks To what extent were you included by the participants during the game? F ð1; 58Þ ¼ 67:3, p < :0005 What percentage of throws do you think your received during the Cyberball game? F ð1; 58Þ ¼ 83:9, p < :0005 Rejected–acceptedd F ð1; 57Þ ¼ 24:3, p < :0005 Computer Inclusion ðn ¼ 18Þ Ostracism ðn ¼ 15Þ Inclusion ðn ¼ 17Þ Ostracism ðn ¼ 12Þ 6.4 (1.5) 3.4 (2.1) 6.5 (1.7) 3.7 (2.3) 6.4 (1.7) 3.2 (1.6) 5.8 (1.7) 3.8 (1.9) 7.1 (1.2) 5.6 (2.1) 6.9 (1.1) 5.5 (2.1) 6.8 (1.4) 3.8 (1.8) 6.5 (1.5) 3.7 (1.7) 6.5 (1.2) 6.4 (1.4) 6.5 (1.1) 6.5 (1.2) 4.9 (2.4) 2.8 (2.0) 4.5 (2.2) 2.9 (2.5) 1.8 (1.6) 2.1 (1.5) 1.2 (.39) 3.3 (2.5) 7.1 (1.6) 2.7 (2.0) 6.1 (1.8) 2.8 (2.1) 37.1 (13.9) 8.3 (4.8) 40.1 (17.8) 9.3 (7.5) 6.8 (1.5) 4.0 (2.1) 6.2 (1.9) 4.2 (2.2) a Each fundamental need score represents an average of three questions. All F values refer to signiﬁcant ostracism vs. inclusion main eﬀects. c Total mood score was an average of four 9-point bipolar questions. d This was a 9-point scale with rejected–accepted as anchors. b participants failed to perceive me as a worthy and likeable person,’’ ‘‘I felt somewhat inadequate during the Cyberball game’’), and meaningful existence (‘‘I felt that my performance [e.g., catching the ball, deciding whom to throw the ball to] had some eﬀect on the direction of the game,’’ ‘‘I felt non-existent during the Cyberball game,’’ ‘‘I felt as though my existence was meaningless during the Cyberball game’’). Mood was assessed using four bipolar questions (bad/good, happy/sad, tense/relaxed, and aroused/not aroused). The questionnaire also contained two ancillary variables (‘‘I felt angry during the Cyberball game’’ and ‘‘I enjoyed playing the Cyberball game’’). Unless otherwise stated, all questions were rated on 9-point scales (where 1 ¼ not at all, and 9 ¼ very much so). After the participants indicated that they had ﬁnished the questionnaire, the experimenter asked participants about their thoughts/feelings during the study, and performed a verbal manipulation check by asking participants whether they had played the game with university students or computer players. They were then thoroughly debriefed about the aims of the study, thanked, and given course credit for participating in the study. Results Manipulation checks. There were three manipulation checks assessing inclusionary status. As shown in Table 1, participants in the ostracism condition reported that they felt signiﬁcantly less included and more rejected than participants in the inclusion condition (smallest F was for rejection, F ð1; 57Þ ¼ 24:3, p < :0001). Participants in the ostracism condition also reported that they received the ball less often during the game than participants in the inclusion condition, F ð1; 58Þ ¼ 83:9, p < :0001.2 This suggests that participants correctly perceived whether they were included or ostracized during the game. To assess the source manipulation, a verbal manipulation check was carried out at the end of the study prior to debrieﬁng. All but two participants correctly identiﬁed whether they played the game with computer or human players. The two aberrant participants (both in the human players condition) reported having played the game with two computers rather than two humans. 2 Degrees of freedom vary slightly in the analyses here and in Study 2 because of occasional missing data. ARTICLE IN PRESS 4 L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx The game had malfunctioned during their participation (a factor that may have led them to realize that they could not have been playing with two humans). Consequently, their self-report data were not included in the analysis. Self-reported levels of needs. The items assessing the four needs (state measures of belonging, control, selfesteem, and meaningful existence) were reverse scored where necessary and the internal consistency of the items assessing each need were examined. CronbachÕs alpha coeﬃcients for each need were: belonging ¼ 74; control ¼ 72; self-esteem ¼ 70; and meaningful existence ¼ 66. The coeﬃcients suggested a reasonable level of internal consistency for each need; thus the average for the items assessing each need were used in the analysis. The main ﬁndings of this study, that ostracized participants reported lower levels of the needs independent of the source, can be seen in Fig. 1 (which depicts a composite score for the four conditions tested in this study). Statistical analysis of each need (see Table 1 for all descriptive statistics) revealed that ostracized participants reported lower levels on each of the four needs measured, smallest F ð1; 57Þ ¼ 11:1, p ¼ :002, for selfesteem. There were no signiﬁcant main eﬀects for source identity on self-reported needs, nor did the inclusionary status interact with the source manipulation, all F s < 1:4, ns. Mood. The mood items were reverse scored where necessary (so that a higher score ¼ more positive mood) and an average mood score was calculated. There were no signiﬁcant main eﬀects or interactions for mood, all F s < 1:0, ns. Ancillary variables. Ostracized participants reported feeling angrier than included participants (see Table 1), Fig. 1. Mean self-reported levels of combined needs of belonging, control, self-esteem, and meaningful existence, as a function of inclusion or ostracism, and by either human or computer in Study 1. F ð1; 58Þ ¼ 8:2, p ¼ :006. There was no main eﬀect for whether they played with humans or computers, but there was a signiﬁcant interaction, F ð1; 58Þ ¼ 4:7, p ¼ :034, such that anger was higher only when they were ostracized by the computer. Ostracized participants reported enjoying the game less compared with included participants, F ð1; 58Þ ¼ 10:2, p ¼ :002. There was no signiﬁcant main eﬀect of source identity, or interaction between inclusionary status and source identity, for enjoyment of the game, both F s < 1, ns. Discussion In Study 1, we found that compared to included participants, ostracized participants reported lower levels on the state measures of the four needs. Moreover, ostracized participants also reported feeling angrier and enjoyed the game less than included participants. Contrary to our expectations, mood reports were not affected by ostracism. It should be noted, however, that the literature to date is surprisingly inconsistent on the eﬀects of social exclusion on mood. That is, while some have reported worsened mood following ostracism (Williams, 2001) or rejection (Leary, Koch, & Hechenbleiker, 2001), others have failed to see an eﬀect on mood following social exclusion (Twenge, Baumeister, Tice, & Stucke, 2001; Twenge, Catanese, & Baumeister, 2002). Although the ostracism manipulation adversely affected participants in accordance with previous ostracism research, whether participants were ostracized by humans or the computer had no eﬀect on their self-reported need levels, or enjoyment of the game. Oddly enough, the only impact that the human/computer manipulation had was the unexpected interaction showing that being ostracized by a computer made participants angrier than being ostracized by humans. Based on comments made during the interviews it would seem that this result was due to a violation of the basic assumption that the computer is a tool to serve humans and hence should not deliberately act to distress or alienate them. For example, one participant (who happened to be a computer programmer) stated that he felt incredibly angry and frustrated during the game because ‘‘the computer is supposed to serve me. ItÕs not supposed to reject me.’’ Why would individuals report lower levels of belonging, control, self-esteem, and meaningful existence when they have experienced ostracism in a 6-min game of virtual ball toss, regardless of whether they were playing with humans or a computer? We believe that initial reactions to ostracism are, in BrewerÕs (2003) terms, ‘‘deep,’’ rather than ‘‘high.’’ That is, it is our position that ostracism has such adaptive signiﬁcance for humans that there is essentially an early warning ARTICLE IN PRESS L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx system that is quick to perceive social exclusion and feel the associated pain, so that the individual is motivated to make changes that will eliminate the ostracism. One potential problem with Study 1 is that participants were not asked to indicate on the post-experimental questionnaire whether they believed they were playing the game with humans or computers. Although we assessed their perceptions in a post-experimental interview, it is possible that experimenter bias may have inﬂuenced our perceptions of their answers. Thus, although we think this is rather implausible, it is possible that participants simply did not attend to our instruction about who they were playing the ball game with, and that is why we found no main eﬀects or interactions with the human/computer manipulation on the self-reported needs. That we found one interaction on the measure of anger (in an unexpected direction, we might add), argues against this criticism that participants were not attentive to the human/computer manipulation; however, it is possible that this interaction was spurious. Therefore, in Study 2, we added explicit manipulation checks to the post-experimental questionnaire assessing the participantsÕ understanding of with whom they were playing. In Study 2, we also extended the present experimental design by adding a third factor: perceived choice of the source. It may well be that to feel threats to the four needs an individual must attribute some sort of sinister intent on the part of the sources (Kramer, 1994). What if we told them that the players with whom they were playing were following a script that had been provided to them, and that they had no choice but to throw the ball to the individual that the script indicated? If the needs that are threatened by ostracism require some higher level interpretation of the ostracism event, then we would expect this manipulation to eliminate the negative impact when participants viewed the ostracism behavior of the sources as outside their control. If, however, the fundamental needs are aﬀected without cognitive intervention, then manipulations aimed at reducing sinister attributions may have no impact at all. Study 2 In Study 2, we examined whether providing an explicit and external reason for ostracism reduced its negative impact. If ostracized individuals know that the reason they are not being thrown the ball has nothing to do with them personally, but rather the other participants (be they human or computer) are simply following a script, will they still report reduced levels of the four needs? If so, we believe this suggests that it is the perception of oneÕs own ostracism, not oneÕs understanding of it, that is immediately threatening. Thus, participants in Study 2 were either included or ostracized from the Cyberball game by two human 5 players or two computer-generated players. In addition, half of the participants were informed that the players (whether human or computers) were playing Cyberball according to a script given to them by the experimenter. This script instructed the players to whom they were to throw the ball every time it was their turn to play. Study 2 also included self-report manipulation checks to supplement the verbal manipulation checks used in Study 1, and some additional questions were asked to assess other aspects of the Cyberball experience. Method Participants and design Seventy-seven undergraduates (30 males, 41 female, M age ¼ 19:6 years, SD ¼ 1:9) enrolled in introductory psychology at the University of New South Wales were randomly assigned to a 2 (inclusionary status: inclusion vs. ostracism) 2 (source identity: computer generated vs. university students) 2 (attribution of choice: scripted vs. unscripted) between-S design.3 Participants volunteered to take part in the experiment in exchange for course credit. Procedure The experiment was conducted on eight versions (one per condition) of an Internet website, which were identical to those used in Study 1 except for modiﬁcations to the cover pages to accommodate the attribution of choice manipulation. The ostracism/inclusion and source identity manipulations were identical to those used in Study 1. Attribution of choice manipulation. In the scripted conditions, the cover page instructed participants that the other players (whether computer generated or human) would be playing the game according to a script, and hence their actions were not spontaneous. In the unscripted condition, participants were instructed that the game was spontaneous and the players were free to throw the ball to whomever they chose (in the case of the computer-generated players, this spontaneous action was explained by saying that the players would be throwing the ball randomly). In all conditions, participants were reminded that they were free to throw the ball to whomever they chose. Dependent measures. The questionnaire was essentially the same as that used in Study 1, with the addition of manipulation check for source identity (‘‘Did you play the Cyberball game with: two students from Macquarie and Sydney University or two computer-generated players?’’) and attribution of choice (‘‘Was the sequence of throws by Player 1 and Player 2 scripted/ 3 Initially, 120 participants were recruited, but a computer virus prevented 43 participants from any form of participation. ARTICLE IN PRESS 6 L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx Results pre-programmed or spontaneous?’’). One additional question was added to examine whether the manipulations led participants to feel emotionally hurt (‘‘My feelings were hurt during the game’’). After the participants completed the game, they were directed to complete the post-study questionnaire. Debrieﬁng. As in the previous experiment, the experimenter asked participants to state whether they had played the game with two human players or two computers, and whether or not the game had been scripted or unscripted. The experimenter then fully debriefed participants, ensuring that they were aware that they were randomly assigned to conditions. Participants in the ostracism condition were carefully debriefed about all aspects of the game, and were given extra information about the nature of ostracism. After answering any remaining questions, participants were then thanked and dismissed. Manipulation checks. As shown in Table 2 (where means and standard deviations can be found for all dependent variables), our manipulations were perceived as intended. Participants in the ostracism condition reported that they felt less included than participants in the inclusion condition, and more rejected, (smallest F was for rejection, F ð1; 69Þ ¼ 25:6, p < :0005). They also reported receiving the ball less often during the game than included participants, F ð1; 66Þ ¼ 117:8, p < :0001 The source identity manipulation was also successful in that only 2% of participants incorrectly identiﬁed the identity of the players, and 4% of participants incorrectly identiﬁed the attribution of choice manipulation. Because there was no computer malfunction that could easily account for these incorrect reports, all participants were retained in the analyses. Table 2 Means and standard deviations (in parenthesis) of variables in Study 2 (all scales 1 ¼ not at all to 9 ¼ very much so, unless otherwise stated) Source Human Computer Inclusion Fundamental needsa Belonging F ð1; 69Þ ¼ 74:8, p < :0005b Control F ð1; 69Þ ¼ 55:0, p < :0005 Self-esteem F ð1; 69Þ ¼ 25:2, p < :0005 Meaningful existence F ð1; 69Þ ¼ 68:0, p < :0005 Moodc F ð1; 69Þ ¼ 6:2, p ¼ :015 Ancillary variables I felt angry during the Cyberball game F ð1; 69Þ ¼ 13:2, p ¼ :001 I enjoyed playing the Cyberball game F ð1; 69Þ ¼ 22:2, p < :0005 My feelings were hurt during the Cyberball game F ð1; 69Þ ¼ 8:3, p ¼ :005 Manipulation checks To what extent were you included by the participants during the game? F ð1; 69Þ ¼ 122:7, p < :0005 What percentage of throws did you receive during the Cyberball game? F ð1; 69Þ ¼ 117:8, p < :0005 Rejected–acceptedd F ð1; 69Þ ¼ 25:6, p < :0005 a Ostracism Ostracism Scripted ðn ¼ 12Þ Unscripted Scripted ðn ¼ 8Þ ðn ¼ 7Þ Unscripted Scripted ðn ¼ 11Þ ðn ¼ 9Þ Unscripted Scripted ðn ¼ 10Þ ðn ¼ 9Þ Unscripted ðn ¼ 11Þ 5.8 (1.5) 6.3 (2.0) 3.6 (1.9) 2.8 (1.2) 5.8 (1.6) 6.4 (1.4) 3.0 (1.4) 2.7 (1.3) 5.8 (1.6) 6.8 (2.2) 2.7 (.90) 3.2 (1.5) 4.7 (.98) 5.5 (2.3) 2.9 (.96) 3.2 (1.6) 6.9 (1.0) 7.6 (1.3) 6.1 (1.7) 5.1 (1.9) 6.3 (2.1) 7.7 (1.6) 4.5 (1.7) 5.4 (1.4) 6.1 (1.6) 7.6 (1.1) 2.8 (1.4) 3.6 (2.1) 5.7 (1.4) 6.2 (1.3) 3.7 (1.8) 3.7 (1.3) 6.8 (1.4) 6.7 (1.4) 6.1 (1.3) 6.0 (1.3) 7.0 (.80) 6.6 (1.8) 5.4 (1.7) 6.4 (.88) 1.8 (1.8) 2.0 (2.1) 2.1 (1.4) 2.8 (1.8) 2.2 (1.5) 1.0 (.00) 4.0 (2.2) 4.0 (2.2) 4.6 (2.3) 6.6 (1.8) 3.3 (1.5) 3.0 (1.7) 5.1 (1.8) 5.2 (2.2) 3.3 (2.2) 3.5 (1.8) 2.2 (2.4) 1.1 (.35) 1.1 (.38) 3.2 (2.2) 2.1 (1.8) 1.2 (.42) 4.3 (2.7) 3.0 (2.2) 6.2 (1.5) 6.9 (2.0) 2.4 (.53) 2.6 (1.5) 5.3 (1.7) 6.0 (1.9) 2.2 (.44) 2.6 (.69) 35.9 (14.2) 45.3 (15.0) 11.7 (8.5) 13.9 (8.2) 43.9 (7.7) 45.8 (13.9) 15.7 (9.1) 13.1 (4.6) 6.3 (1.8) 4.2 (2.0) 6.3 (1.9) 5.7 (2.6) 3.5 (1.9) 6.9 (2.2) 4.4 (2.1) Each fundamental need score represents an average of three questions. All F values refer to signiﬁcant ostracism vs. inclusion main eﬀects. c Total mood score was an average of four 9-point bipolar questions. d This was a 9-point scale with rejected–accepted as anchors. b Inclusion 3.4 (2.1) ARTICLE IN PRESS L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx Self-reported level of needs. As in Study 1, the items assessing each need were reverse scored where necessary and the internal consistency of the items were assessed. CronbachÕs alpha coeﬃcients for each need were as follows: belonging ¼ .71; control ¼ .80; self-esteem ¼ .76; and meaningful existence ¼ .69. The coeﬃcients suggested a reasonable level of internal consistency for each need; thus the average for the items assessing each need were used in the analysis. As in the previous study, there were signiﬁcant main eﬀects for inclusionary status on the four needs such that participants who were ostracized reported lower levels of belonging, control, self-esteem, and meaningful existence than participants who were included in the game, (smallest F was for self-esteem, F ð1; 69Þ ¼ 25:2, p < :0005). There were no signiﬁcant main eﬀects for source identity on the primary needs (largest F was for control, F ð1; 69Þ ¼ 2:2, p ¼ :147). Attribution of choice did not aﬀect self-reported need levels for belonging, control, or self-esteem, but there was a marginally signiﬁcant main eﬀect for meaningful existence, such that participants who believed the game was unscripted (free choice) reported higher levels of meaningful existence than participants who believed the players were scripted, F ð1; 69Þ ¼ 3:9, p ¼ :052. There was also a marginally signiﬁcant interaction between inclusionary status and source identity for meaningful existence, F ð1; 69Þ ¼ 3:95, p ¼ :051. Follow up analyses revealed that the eﬀects of inclusion and ostracism on self-reported meaningful existence produced more extreme diﬀerences when the sources were human than when the sources were computers. No other two-way interactions for the remaining needs were signiﬁcant, nor were there any signiﬁcant three-way interactions. Mood. The mood items were reverse scored where necessary (so that a higher score equalled more positive mood) and an average mood score was calculated. Participants in the ostracism condition reported feeling more negative during the game than participants in the inclusion condition, F ð1; 69Þ ¼ 6:2, p ¼ :015. There were no signiﬁcant main eﬀects for source identity or attribution of choice, nor were there any signiﬁcant two or three way interactions, all Fs < 1:5, ns. Ancillary variables. There were several eﬀects of inclusionary status on the ancillary variables. Speciﬁcally, participants who were ostracized reported feeling angrier, more hurt, and that they enjoyed the game less than participants who were included in the game, (smallest F was for anger, F ð1; 69Þ ¼ 8:3, p ¼ :005). There were no signiﬁcant main eﬀects for source identity or attribution of choice on the ancillary variables. There was a signiﬁcant two-way interaction between inclusionary status and source identity for anger, F ð1; 69Þ ¼ 5:0, p ¼ :028. Follow up analyses revealed that participants who were included were no more angry 7 if playing a computer or humans, but as in Study 1, ostracized participants were angrier at being ostracized by a computer than humans, F ð1; 34Þ ¼ 5:4, p ¼ :026. No other two-way interactions were signiﬁcant. There was a signiﬁcant three-way interaction for hurt feelings, F ð1; 69Þ ¼ 4:0, p ¼ :049, which suggested that when interacting with humans, participants reported higher levels of hurt feelings only when they were ostracized by two players who had free choice as to whom they could throw the ball. Participants who played the computer, however, reported more hurt feelings simply when they were ostracized, regardless of whether or not the computer game had been scripted. Discussion The results of Study 2 largely replicated the ﬁndings of Study 1. Once again, we found that ostracism resulted in lower self-reported levels of four needs. However, in Study 2 we also found that ostracism resulted in less positive mood than did inclusion. Thus, the inconsistent nature of mood eﬀects following social exclusion that exists in the broader literature was mirrored in our two studies. We regard this inconsistency as evidence of the less than robust eﬀect of social exclusion on mood. In any case, as Twenge et al. (2001, 2002) and Williams et al. (2000) have also demonstrated, regardless of whether mood is aﬀected by social exclusion, it does not mediate need levels nor subsequent behaviors. More importantly for the present investigation, ostracism by computers was just as unpleasant as ostracism by humans, and furthermore, it did not matter whether the human or computer players were perceived to have a choice as to whom they threw the ball. Thus, once again, it appears that ostracism, per se, is felt immediately as a negative and depleting experience. ParticipantsÕ initial reactions to a short exposure to ostracism were not aﬀected by two factors that would generally be regarded as rendering the ostracism experience meaningless: being ignored and excluded by a computer, and knowing that the players were told (or programmed) not to throw the ball to them. Instead, within minutes, feelings of belonging, control, self-esteem, and meaningful existence are reduced, simply because the participants were not thrown a ball while playing a relatively meaningless game that had no winners or losers, with people who they do not know and will not meet.4 4 As one reviewer suggested, it is possible that participants viewed the scripted conditions as an attempt to ostracize them by the experiment. Although we do not have any measures to explicitly address this possibility, this suggestion would lead to an expectation of stronger eﬀects under the scripted conditions (for human or computer sources), which we did not ﬁnd. ARTICLE IN PRESS 8 L. Zadro et al. / Journal of Experimental Social Psychology xxx (2004) xxx–xxx General discussion The ﬁndings of both studies lead us to conclude that ostracism is such an important warning signal that individuals are pre-cognitively attuned to its employment on them. For primates, and many other species (see Williams, 2001), ostracism means death. For humans, it surely signals the potential for hard times, possibly loss of contact with important others, loss of resources, and in some cases, death. Hence, it appears that even the slightest hint of ostracism, in the present case by a computer, is enough to trip oﬀ emotional reactions that will activate coping strategies to increase oneÕs subsequent inclusion. Our ﬁnding that individuals can react to computers in a similar fashion to how they react to humans is also consistent with NassÕs work on human–computer interactions (e.g., Reeves & Nass, 1996). In a variety of clever studies, Nass and his colleagues have shown that humans will reciprocate self-disclosures, be more strategically polite, and form in-group alliances with computers, just as they have been shown to do with other people. Whether this means that we anthropomorphize computers, enact mindless scripts to guide our social behaviors, or that we have such a deep-rooted need to belong that it can be fulﬁlled by computers (as exempliﬁed in Steven SpielbergÕs AI where the mother grew to love a Cyborg son), is the subject matter for future investigations. We remain motivated to ﬁnd conditions that involve ignoring and exclusion but that are so minimal as to not inﬂict emotional damage. Based on the present ﬁndings, it appears that this search for the necessary and suﬃcient conditions for ostracism, at least when measured during or soon after the ostracism, may be diﬃcult or impossible. It appears that ostracism is such a powerful signal that even being ignored by a computer can activate strong reactions. Indeed, Eisenberger, Lieberman, and Williams (2003) showed activation of the anterior cingulate cortex—the brain region that is also activated when individuals endure physical pain—as a result of Cyberball ostracism, even when the participants were told their particular computer was not yet linked to the other two participantsÕ computers. We are also examining the impact of these simple acts of ostracism on participantsÕ cardiovascular responses (Zadro, Barker, Richardson, & Williams, 2001; Zadro, Walker, Williams, & Richardson, 2000). The amassed evidence suggests that at all levels of measurement, humans detect and suﬀer from the most minimal cues of ostracism, supporting our view that ostracism is such a powerful social signal that it produces widespread intrapsychic reactions that serve to mobilize coping responses (see also, Panksepp, 2003). References Brewer, M. (2003). Implicit and explicit processes in social judgments and decisions: An integration. In J. P. Forgas, K. D. 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