JOURNAL OF RESEARCH IN PERSONALITY 10, 5%8 (1976)

Attraction and Altruism: With a Little Help from My Friends

KATHRYN KELLEY AND DONN BYRNE

Purdue University

The present experiment was designed to determine whether the reinforcement value of an altruistic response is a function of attraction toward the victim and/or the affective state of the subject. Subjects (N = 95) received positive or negative evaluations from a victim or from a bystander and subsequently performed an altruistic response which terminated shock delivery to a victim on a series of 14 trials. Analyses of variance indicated that the acquisition of an altruistic response was greatest when attraction toward the victim was most positive @ < .OOOl) and nonexistent when attraction toward the victim was least positive. The results were consistent with the proposition that attraction rather than affect mediates altruistic reinforcement. Those subjects receiving negative evaluations from the victim failed to acquire the altruistic response, suggesting that failure to help may function as a form of passive aggression.

The investigation of altruistic behavior has been characterized by numerous imaginative studies in both the laboratory and the field. Such work has identified a series of antecedents of differential altruism, includ- ing the number of spectators (Latank & Darley, 1%8), cultural norms (LatanC & Dabbs, 1973, reason for disablement (Piliavin, Rodin, & Piliavin, 1%9), the implicit rules governing the situation (Staub, 1971), and the ambiguousness of the emergency (Yakimovich & Saltz, 1971). Theore- tical explanations of prosocial behavior have involved both the descriptive decision-making sequence outlined by Latani and Darley (1970) and efforts to explain altruism as a function of reinforcement.

Within the reinforcement framework, it has been shown that the proba- bility of an altruistic response varies as a function of having been reinforced for such behavior in the past (Moss &Page, 1972) and that the act of helping another person is itself a reinforcer (Weiss, Buchanan, Alstatt, & Lom- bardo, 1971). The reinforcement-affect model of Clore and Byrne (1974) suggests that the reinforcing effects of interpersonal responses such as altruism may be attributed to one or both of two related mediator variables. Specifically, the reinforcement value of an altruistic act may be a function

This research was supported in part by a Bureau of Indian Affairs Higher Education Scholarship through the United States Department of Interior to Kathryn Kelley and in part by National Science Foundation Grant GS-40329, Donn Byrne, principal investigator. Re- quests for reprints should be sent to Donn Byrne, Department of Psychological Sciences, Purdue University, West Lafayette, IN 47907.

59 Copyright @I 1976 by Academic Press, Inc. All rights of reproduction in any form reserved.

60 KELLEY AND BYRNE

of attraction toward the recipient (e.g., Baron, 1971; Daniels & Berkowitz, 1%3; Staub & Sherk, 1970) and/or a function of the affective state of the subject (Isen, 1970; Isen, Horn, & Rosenhan, 1973; Isen & Levin, 1972).

Viewed in this context, it is essential to be able to specify the conditions under which helping another person functions as a reinforcement. It may be that any act of altruism is reinforcing, regardless of the relationship be- tween subject and victim or of the subject’s emotional state as Weiss et al. (1971) imply. Alternatively, it is proposed that altruism is reinforcing only when the subject is attracted to the victim or only when the subject’s affective state is positive. If either of the latter two propositions are correct altruism toward a disliked victim or when the subject is experiencing negative affect would not be expected to be positively reinforcing, and, hence, would not be learned.

The investigation of the differential effects of attraction and affect is complicated because attraction and affect tend to vary concomitantly (Byrne, 1971). Work within the attraction paradigm suggests a procedure for differentiating the two variables, however. When a subject receives positive or negative evaluations from another person, both attraction (Byrne & Griffitt, 1966; Byrne & Lamberth, 1971; Byrne, Rasche, & Kelley, 1974; Byrne & Rhamey, 1965; Clore & Baldridge, 1970) and feeling state (Griffitt & Guay, 1969; Singh, 1973) are subsequently affected. If two strangers are present, however, there is the possibility of differentiating affect and attraction in that evaluations from either person produce an equivalent influence on affect, while attraction is more strongly influenced toward the individual making the evaluation than toward the bystander (Hughes, 1969). In other words, a generalization gradient yields greater attraction toward the source of the evaluation than toward an individual simply associated with the source temporally or spatially. In the present investigation, the subject is evaluated by either the victim or by a bystand- er. If the reinforcement value of altruistic behavior toward the victim in the two situations is the same the role of affect as a mediator would be supported. The finding of a differential reinforcement value of altruism toward the victim in the two situations would support the proposition that attraction is the mediating variable.

A way to measure the reinforcement value of altruistic responses under differential conditions has been provided by Robert Weiss and his as- sociates at the University of Oklahoma. Since subjects have been shown to respond in a prosocial manner to indications of pain and suffering on the part of a victim (Baron, 1971,1974; Geer & Jarmecky, 1973), it follows that subjects will learn an instrumental response which terminates a shock being delivered to a suffering victim. In confirmation of this line of reason- ing, the Oklahoma group has been able to show that when subjects have the opportunity to learn an altruistic instrumental response, they do so (Weiss,

ATTRACTION AND ALTRUISM 61

Boyer, Lombardo, & Stich, 1973; Weiss, Buchanan, Altstatt, & Lombar- do, 1971). These experiments further demonstrate that altruistic rein- forcement parallels more traditional reinforcers with respect to the effect of such variables as continuous versus partial reinforcement and delayed versus immediate reward. In the present experiment, performance in this learning situation was utilized to determine whether the reinforcement value of altruism is mediated by affect or attraction.

General Description METHOD

Each subject responded to an attitude survey prior to the experimental session. In the experiment proper, the subject inspected evaluations of himself supposedly made either by a confederate (the victim) or by another student who was not present in the room (the bystand- er). These evaluations were either positive or negative. In a control group, there were no evaluations of the subject.

During 14 acquisition trials, the subject pulled a lever to terminate shock being delivered to the victim. Speed of shock termination was the measure of altruism. Attraction to the victim and to the bystander was measured by standard rating scales.

Subjects and Design The subjects were 30 male and 65 female undergraduate psychology students at Purdue

University. Each subject’s responses to a 12-item Survey of Attitudes (Byrne, 1971) were obtained 2 to 3 days before the experimental session. The survey contained items such as opinions toward the women’s movement and liberalization of marijuana laws.

The subjects were randomly assigned to one of the four experimental groups or to the control group, with a total of 19 subjects in each cell.

The dependent measure of altruism was the number of seconds recorded in hundredths (1OOfiatency) to terminate shock to a suffering victim following illumination of a signal light. With seven trial blocks of two trials each, the experiment was based on a 2 (evaluation) by 2 (source) by 7 (trials) repeated measures design with one control group. Attraction to the victim was measured by the Interpersonal Judgment Scale (Byrne, 1971), and a modified version of this scale was used to measure attraction toward the bystander.’ This instrument consists of six seven-point Likert scales, the first four of which are buffer items. The last two items are summed to yield a measure of attraction ranging from two (most negative) to 14 (most positive).

Procedure The subject was escorted by the experimenter to the laboratory from an adjacent area and

was seated in a cubicle connected to the experimental room by a two-way mirror. The

*Attraction was assessed rather than both attraction and affect for two reasons. First, affect has been found previously to be influenced by personal evaluations, regardless of source (Singh, 1973), but the predicted differential attraction effect has previously been established only in an unpublished experiment by Paul Bleda at Purdue. In one experiment, the predicted relationship failed to appear (Griffitt & Guay, 1%9). Therefore, while it was essential to document the attraction effect, further data on affect in this situation would have been redundant. Second, it has been shown that the assessment of affect interferes with the subsequent assessment of attraction (Hodges & Byrne, 1971) presumably because of the affect neutratization effect (Byrne, Lamberth, Palmer, & London, 1969).

62 KELLEY AND BYRNE

experimenter described the first part of the study as one dealing with impression formation, telling the subject that the attitudes he had endorsed in the earlier session had been read and evaluated by another same-sex subject. This evaluator was identified as either the confederate (who was to play the role of victim) or as another subject not present in the room (who is designated here as the bystander). The individual making the evaluations supposedly was uninformed as to the identity of the individual being evaluated. Before the evaluations were received by the subject, the experimental task was introduced.

The subject and victim were placed in the same experimental room, and the instructions were given. The confederate-victim was blind to the experimental condition to which the subject was assigned. The participants were informed that the study’s orientation to the human factors area of psychology required observance of the effects of physical stress (in the form of electric shock) on task performance and physiological responses. Comparable real-life tasks such as driving an automobile or flying an airplane were mentioned as examples of activities that might benefit from such knowledge. It was said that valuable information could potentially be obtained from an observer, since it was possible to record the observer’s evaluation of the other person’s performance under stress. If the observer could adequately gauge the impairment of performance relative to the physiological responses in the sufferer it might someday be possible to prevent accidents in driving or flying by utilizing such an observer.

After electrodes were attached to the victim, his task was explained. A pointer fixed to a rotatable wheel was to be kept centered on a metal spike. It was suggested that this task of steadying the wheel and centering the pointer would be made quite difficult by the periodic delivery of electric shock. The wheel assembly was placed directly in front of the victim, flat on the table. It was said that the electrodes would deliver a painful but not harmful shock, and that galvanic skin response would be measured. In addition, the total time the pointer was kept centered during shock delivery would supposedly be measured electronically.

The subject’s task was to observe and evaluate the victim’s performance. By means of headsets, the experimenter announced “shock on,” “evaluation one,” “evaluation two,” “evaluation three,” and “report” on each 40-set trial. When the subject heard “shock on,” he was to observe for 10 set the victim’s performance. After each evaluation announcement, at lO-set intervals, the subject was to evaluate the victim on a IO-point scale by turning dials indicating the respective variables of control, effort, and success. For example, a victim might appear to a subject to have poor control of the pointer and to be expending a great deal of effort in accomplishing the task moderately well. In this instance, the victim’s performance would be rated low on control, high on effort, and medium on success for that trial. The final report signal coincided with a light which was the signal to depress a lever purported to record the three evaluations electronically. The lever turned off the signal light and was described as shutting off the electricity for a IO-set rest period.

After the task was described to the subject, he was reminded that both the victim and a bystander had read his attitude scale and evaluated him, but that only one of the evaluations would be given to him. The subject was asked to read the judgments about himself and to try to form an opinion of the evaluator. The procedure followed that of Byrne and Rhamey (1965). Subjects in the positive evaluation conditions were informed that the victim or the bystander considered them to be very much above average in intelligence, very much above average in knowledge of current events, moral, well adjusted, and as someone who would be liked very much and with whom he would very much enjoy working. Those in the negative evaluation conditions were informed that the source considered them to be below average in intelligence, slightly below average in knowledge of current events, immoral to a slight degree, maladjusted to a slight degree, and as someone who would be disliked very much and with whom he would very much dislike working.

After a practice trial without electricity, 14 experimental trials were run. The one male and two female confederates were pretrained to exhibit a high degree of stress for the duration of

ATTRACTION AND ALTRUISM 63

each shock period by groaning, jerking, and showing signs of physical exhaustion. Profuse sweat on the victim’s forehead, hands, and arms heightened the reality of the performance. When the “shock off” signal was given, the victim sighed in relief and leaned back in the chair.

Apparatus The apparatus used by the subject was a gray masonite panel 30 by 30 in. with a lever in the

center which could be depressed 15 in. At the upper right of the panel was a signal light with three movable dials under it. The dials were labeled “Control,” “Effort,” and “Success.” Two stop clocks (Lafayette Model 20225A) were wired to the lever. When the signal light was illuminated, clock one was activated. When the subject began to depress the lever, clock one was terminated and clock two was activated. When the lever reached the bottom of the 15 in. slit, the signal light and clock two were terminated.

The apparatus used by the victim consisted of a gray steel panel 15 by 15 in. with a rubber wheel attached horizontally to the panel’s center. The wheel was 8 in. in diameter and 1 in. in width, and it could be fully rotated. A 2 in. steel pointer was fixed to the wheel’s underside and a steel cylinder 1% in. in diameter was attached to the top center of the panel. Inoperative sets of electrodes were attached to the victim’s forearm and fingers on the side nearest to the subject who sat 2 ft. away.

The experimenter monitored the clocks and a Hunter interval timer wired to the apparatus behind the subject’s panel. In addition, an amplifier and the experimenter’s microphone provided a communication link to the subject and the victim through their individual headsets.

Attraction Following the 14 trials, the experimenter removed the victim’s electrodes and allowed him

to leave with a debriefing questionnaire. Then the subject was asked to express his opinion about the victim on the Interpersonal Judgment Scale. To assess the subject’s attraction toward the bystander, only the two attraction items were administered.

Debriejing A full explanation of the experiment and a debriefing form were provided for each subject.

In response to questioning about the credibility and goals of the experiment, no subjects indicated any suspicion of the actual purpose of the study. A small number guessed that altruism was involved (by way of the evaluations), but none assumed that the speed with which the lever was pulled was of interest to the experimenter.

RESULTS

Attraction Manipulation The goal of the attraction manipulation was not only to evoke differential

attraction toward a positive and a negative evaluator but also to create a greater positive-negative difference in attraction toward an evaluating victim than toward a victim simply associated with the evaluations of a bystander. In other words, with respect to the subject’s attraction toward the victim, an interaction was expected between type of evaluation and source of evaluation; such an interaction constituted crucial evidence of the success of the manipulation. As suggested by the means in Table 1, both the main effect of evaluation [F (1, 72) = 39.18, p < .OOOll and the interaction between evaluation and source [F (1,72) = 8.09,~ < .0061 were

64 KELLEY AND BYRNE

TABLE 1

ATTRACTION TOWARD VICTIM AS A FUNCTION OF EVALUATIONS RECEIVED BY SUBJECT FROM THE VICTIM OR FROM A BYSTANDER

Evaluations

Source of evaluations Negative Positive

Victim 9.58 12.95 Bystander 10.74 12.00

significant. Thus, evaluations from either source influenced attraction to- ward the victim, but the effect was greater when the victim was the evaluator than when the bystander was the evaluator. A Newman-Keuls analysis indicated that the negative evaluations from the victim resulted in lower attraction responses than in the other three cells (p < .Ol).

Though it is irrelevant to the present experimental goals, it is important to the validity of our procedures to note that attraction toward the bystand- er would be expected to show precisely the same kind of differences as attraction toward the victim, only in reverse. As hypothesized, attraction toward the bystander also varied as a function of evaluation [F (1, 72) = 48.93, p < .OOOl] and of the interaction between evaluation and source [F (1,72) = 19.18,~ < .OOOl]. Analogously to the previous finding, evaluations from either source influenced attraction toward the bystander, but the effect was greater when the bystander was the evaluator. A Newman- Keuls analysis indicated even stronger effects in this instance with attrac- tion toward the bystander most positive when the bystander was the source of positive evaluations (p < .Ol) and most negative when the bystander was the source of negative evaluations (p < .Ol).

Altruism

Acquisition curves of response speed on clock one’ for the five groups across the seven two-trial blocks are shown in Fig. 1. A 2 x 2 x 7 trial blocks repeated measures analysis of variance with one control group (Winer, 1971) was performed on the altruism measure. Control group subjects received no personal evaluations, and their speed in shock termi- nation was not different from that of all experimental groups (F < 1). When the control group was compared with each experimental group, only the group evaluated positively by the confederate responded faster than the control group (Dunnett’s t = 2.56, p < .025).

2 Separate analyses of response speed on clock two yielded results which were essentially the same as those reported for clock one.

ATTRACTION AND ALTRUISM 65

3 3 bsitive Evaluation from Victim

Negative Evaluation

FIG. 1. Acquisition curves of altruistic response (speed of lever pressing) over two-trial blocks comparing groups receiving positive or negative evaluation from the victim or from a bystander. A control group did not receive an evaluation from either the victim or from a bystander.

An evaluation x source x trial blocks interaction [F (6,540) = 2.81,~ < .Ol] suggested that the observed evaluation x source interaction [F (1,90) = 18.47, p < .OOOl] should be interpreted in terms of change in response speed over trial blocks. Simple effects analyses over all seven discrete blocks of two trials each indicated that speed increased over trials for the subjects receiving positive evaluations from the victim [F (6,540) = 10.76, p < .OOOl], those positively evaluated by the bystander [F (6,540) = 4.94,~ < .OOl], and those negatively evaluated by the bystander [F (6,540) = 3.60, p < .OOl], but not for those negatively evaluated by the victim (F < 1). The control group also showed improved performance over trials [F (6,540) = 2.10, p < .053. The significant trend effects were linear in the groups positively evaluated by the victim [Fli, (1, 90) = 35.38, p < .OOOll, posi- tively evaluated by the bystander [Fii, (1,90) = 10.57,~ < .OOl], negatively evaluated by the bystander [Fii, (1,90) = 5.45,~ < .OOl], and in the control group [Fli, (1, 90) = 6.52, p < .OOl]. There were no significant deviations from linearity for any of these four groups (p > .50). The Newman-Keuls sequential range test was performed on the means of the seven trial blocks of the experimental groups. These analyses showed that the means of the two groups evaluated by the victim differed from each other (p < .Ol) and from those of the groups evaluated by the bystander (ps < .05). Positive evaluations from the confederate produced more altruism than those ob- served in any other group. In addition, the group receiving negative evalua- tions from the confederate was less altruistic than either group evaluated by the bystander.

Under the assumption that sex differences in altruism and/or attraction were most likely to occur in the groups evaluated by the victim, preliminary analyses of variance were performed on all dependent measures in order to

66 KELLEYAND BYRNE

test for sex differences. The analyses indicated that there were no sig- nificant main effects or interactions attributable to sex. Parallel analyses on the possible effects of the different confederates on the dependent mea- sures indicated no significant main effects or interactions.

DISCUSSION

The results support the proposition that the reinforcement value of an altruistic response varies as a function of attraction toward the victim. With affect held constant, differential attraction was accompanied by differential performance in acquiring an altruistic response. For those subjects. evaluated by the victim, attraction toward the victim and mean response speed over all seven trial blocks were positively correlated (Y = S7, p < .OOl). In the remaining three groups in which there was only minimal differential attraction to the victim, attraction and altruism were not sig- nificantly correlated.

Response to the victim by the subjects in the control group and by those evaluated by a bystander are consistent with the findings of Weiss and his associates. That is, attraction toward a stranger based on no information (control group attraction mean = 10.32) or on affect associated with the evaluations of a bystander is sufficiently positive to elicit altruistic behavior which acts as a reinforcer. When attraction exceeds this level (subjects positively evaluated by the victim), the reinforcement value of an altruistic response is increased. When attraction is sufficiently low (subjects nega- tively evaluated by the victim), the reinforcement value of an altruistic response is decreased to the point that performance does not vary over trials.

Failure to learn the altruistic response may be interpretable as passive aggression. In effect, subjects were able to respond with socially accepta- ble aggression toward someone who had responded negatively to them simply by failing to rush to ameliorate his pain. Strong sanctions against overt aggression may make such passive aggression a more common means of harming others than the overt physically aggressive acts more usually studied in research in this area. The elimination of female subjects from the typical aggression experiment is based on the finding that females are reluctant to cause direct harm to others, as when they must push a button to shock a victim. The similarity in behavior between males and females in the present research suggests that failure to acquire an altruistic response might prove to be a suitable way to study female aggressivity.

The present results are consistent with the general reinforcement in- terpretation of altruism and suggest that attraction is an important mediator of the reinforcement value of altruistic behavior. Other interpretations of the present results may, of course, be suggested. For example, an exchange or equity explanation could be proposed (Adams, 1965; Homans, 1961;

ATTRACTION AND ALTRUISM 67

Waker, Berscheid,,& Walster, 1973). That is, it is possible that those subjects who received positive evaluations from the victim felt obliged to engage in some reciprocal positive behavior-in this instance the faster alleviation of suffering. Because the present experiment was designed to test only the differential mediating effects of attraction and affect, we are in no position to evaluate the differential effects of attraction and the desire for equitable social exchange. If attraction were manipulated within the Weiss paradigm by means of the physical attractiveness of the victim and the results were comparable to those obtained with positive evaluations, the identification of attraction as the crucial variable would be less equivocal. If, on the contrary, attraction in that instance did not have an effect on the reinforcement value of the altruistic response, the present findings could more convincingly be reinterpreted on the basis of exchange theory. Without such data, however, we can only assert that the many findings linking attraction to reinforcement are theoretically and empirb tally compatible with the performance data obtained in the present experi- ment.

REFERENCES Adams, J. S. Inequity in social exchange. In L. Berkowitz (Ed.), Advances in experimenral

social psychology. New York: Academic Press, 1965. Vol. 2, pp. 267-299. Baron, R. A. Aggression as a function of magnitude of victim’s pain cues, level of prior anger

arousal, and aggressor-victim similarity. Journal ofPersonalify and Socia/Psychology, 1971, l&48-54.

Baron, R. A. Aggression as a function of a victim’s pain cues, level of prior anger arousal, and exposure toanaggressive model. Jortrna/ofPersonalityandSocialPsychology, 1974,29, 117-124.

Byrne, D. The atfraction paradigm. New York: Academic Press, 1971. Byrne, D., & Griffitt, W. Similarity versus liking: A clarification. Psychonomic Science, 1966,

6, 295-296. Byrne, D., & Lamberth, J. Reinforcement theories and cognitive theories as complementary

approaches to the study of attraction. In B. I. Murstein (Ed.), Theories ofattraction and love. New York: Springer, 1971. Pp. 59-84.

Byrne, D., Lamberth, J., Palmer, J., & London, 0. Sequential effects as afunction of explicit and implicit interpolated attraction responses. Journal of Personality and Social Psychofogy, 1%9, 13,7&78.

Byrne, D., Rasche, L., & Kelley, K. When “I like you” indicates disagreement: An experi- mental differentiation of information and affect. Journal of Research in Personality, 1974, 8, 207-217.

Byrne, D., & Rhamey, R. Magnitude of positive and negative reinforcements as a determinant of attraction. Journal of Personality and Social Psychology, 1965, 2, 884-889.

Clore, G. L., & Baldridge, B. The behavior of item weights in attitude-attraction research. Journal of Experimental Social Psychology, 1970, 6, 177-186.

Clore, G. L., & Byrne, D. A reinforcement-affect model of attraction. In T. L. Huston (Ed.), Formdationsofinferpersonalattraction. New York: AcademicPress, 1974. Pp. 143-170.

Daniels, L. R., & Berkowitz, L. Liking and response to dependency relationships. Human Relations, 1963, 16, 141-148.

68 KELLEY AND BYRNE

Geer, J. H., & Jarmecky, L. The effect of being responsible for reducing another’s pain on subjects’ response and arousal. Journal of Personaliry and Social Psychology, 1973,26, 232-237.

Griffitt, W., & Guay, P. “Object” evaluation and conditioned affect.Jortma[ofExperimenral Research in Personality, 1969, 4, I-8.

Hodges, L. A., & Byrne, D. Neutralization of attraction and evaluarion responses. Paper presented at the meeting of the Midwestern Psychological Association, Detroit, May 1971.

Homans, G. C. Social behavior: Its elementary forms. New York: Harcourt, Brace, and World, 1961.

Hughes, R. L. “Object” evaluation: A reinterpretation of affect conditioning in the rein- forcement model of attraction. Unpublished master’s thesis, University ofTexas, 1969.

Isen, A. M. Success, failure, attention, and reactions to others: The warm glow of success. Journal of Personality and Social Psychology, 1970, 15, 294-301.

Isen, A. M., Horn, N., & Rosenhan, D. L. Effects of success and failure on children’s generosity. Journal of Personality and Social Psychology, 1973, 27, 239-247.

Isen, A. M., & Levin, P. F. The effect of feeling good on helping: Cookies and kindness. Journal of Personality and Social Psychology, 1972, 21, 384-388.

Latant, B., & Dabbs, J. M., Jr. Sex, group size and helping in three cities. Sociometry. 1975, 38, 180-194.

LatanC, B., & Darley, J. M. Group inhibition of bystander intervention in emergencies. Journal of Personality and Social Psychology, 1968, 10, 215-221.

LatanC, B., & Darley, J. M. The unresponsive bystander: Why doesn’t he help? New York: Appleton-Century-Crofts, 1970.

Moss, M. K., & Page, R. A. Reinforcement and helping behavior. Journal of Applied Social Psychology, 1972, 2, 360-371.

Piliavin, I. M., Rodin, J., & Piliavin, J. A. Good Samaritanism: An underground phenome- non? Journal of Personality and Social Psychology, 1969, 13, 289-299.

Singh, R. Affective implications of rhe weighting coefJicient in attraction research. Unpub- lished doctoral dissertation, Purdue University, 1973.

Staub, E. Helping a person in distress: The influence of implicit and explicit “rules” of conduct on children and adults. Journal of Personality and Social Psychology, 1971, 17, 137-144.

Staub, E., & Sherk, L. Need for approval, children’s sharing behavior, and reciprocity in sharing. Child Del,elopment, 1970, 41, 243-252.

Walster, E., Berscheid, E., & Walster, G. W. New directions in equity research. Journal of Personality and Social Psychology, 1973, 25, 151-176.

Weiss, R. F., Boyer, J. L., Lombardo, J. P., & Stich, M. H. Altruistic drive and altruistic reinforcement. Journal of Personality and Social Psychology, 1973, 25, 390-400.

Weiss, R. F., Buchanan, W., Alstatt, L., & Lombardo, J. P. Altruism is rewarding. Science, 1971, 171, 1262-1263.

Winer, B. J. Statisrical principles in experimental design. New York: McGraw-Hill, 1971. Yakimovich, D., & Saltz, E. Helping behavior: The cry for help. Psychonomic Science, 1971,

23,427-428.