Br.3. soc. clin. Psychol. (1971), 10, pp. 234-240 Printed in Great Britain

Persuasiveness of Confidence Expressed via Language and Body Language

BY CATHA MASLOW, KATHRYN YOSELSON AND

HARVEY LONDON

Brand& University

In previous studies (Johnson & London, 1968; London et al., 1g7oa) expressed confidence has been identified as a new ‘message’ variable causing persuasion. However, the variable has been extracted from naturalistic discussion in a dyad. In order to determine further its efficacy, we manipulated expressed confidence in two studies. In Study I expressed confidence was manipulated via language. In Study 2 expressed confidence was manipulated via body language. The results confirm earlier findings and indicate that a ‘channel’ notion is required to understand the expression of confidence.

A new method of studying persuasion, the ‘jury method’, has recently been developed (London et al., 197ob, c). This technique allows study of the natural behaviour of the persuader in the context of two-person persuasive interaction. No method has heretofore been available which permits random assignment of subjects to opposing points of view with respect to an issue and subsequent observation of subjects as they attempt to resolve their disagreement.

Studies using the jury method have presented evidence that it is the expression of confidence which causes the persuader to change the attitude of the persuadee (Johnson & London, 1968; London et al., 197oa). The ‘expressed confidence’ notion may be distinguished from other, perhaps similar, variables such as credibility and self-esteem (McGuire, 1969a, pp. 182, 250) found to affect attitude change. Using McGuire’s terminological schema (1969a, p. 172), credibility is a source variable and self-esteem is a receiver variable, while expressed confidence is a message variable.”

T o be specific with respect to the ‘expressed confidence’ concept, the words uttered by subjects discussing an issue and attempting to resolve their disagreement may be conceived as expressing confidence (in terms of statements conveying Confidence in Self (C,) and Doubt in Other (Do)) and doubt (in terms of statements conveying Doubt in Self (DJ and Confidence in Other (Co)). In the course of discussion both person A and person B will utter a number of statements relevant to the expression of confidence and doubt and a number of statements that are irrelevant. From the relevant statements uttered by each subject one may derive a ‘vector of persuasion’ which, being directional, necessarily represents both the persuasive force exerted on the other and, simultaneously, the resistance to per- suasion of the self. T o compute the vector one performs a content analysis (Yoselson

* The question may arise whether expressed confidence should be considered a ‘message style’ or a ‘message discrepancy’ variable (cf. McGuire, 1969a, pp. 207, 217). We prefer at this stage in our research to consider expressed confidence a message style variable since such a categorization seems relatively face-valid and theory-free. To consider expressed confidence a message discrepancy variable implies more than we yet know about the mechanism by which expressed confidence persuades.

234

Per.wasiveness of Confidence 235 et al., 1970) of a discussion and, for each subject, simply subtracts from the number of statements indicating confidence the number of statements indicating doubt. That is, vector of persuasion = confidence - doubt = (C, + Do) - (Ds + CJ.

The present report presents two studies which build upon the research we have outlined. The studies cited above have extracted linguistically expressed confidence from naturalistic discussion in a dyad. The inference that expressed confidence caused persuasion was made possible by a process of ruling out alternative explana- tions. This approach to causal analysis has been developed or endorsed by meth- odologists in a number of disciplines (Blalock, 1964; Campbell & Stanley, 1963; Li, 1955 ; McGuire, 1967, 19693; Simon, 1957); nevertheless, any variable whose causal status has been inferred in this way should perhaps also be investigated by more conventional means. For this reason, in Study I we manipulate expressed confidence under stringently controlled conditions. If the amount of confidence expressed within an argument is varied while all other elements of the argument are held constant, and if a confidently expressed argument is shown more persuasive than one less confidently expressed, then the expressed confidence notion gains greater credibility. As mentioned above, the expression of confidence has thus far been measured

via language. However, it is clear that confidence and doubt may be expressed in a variety of ways and that a linguistic measure indexes only one among a number of possible modes.

Therefore, in Study 2 we explore a second potential ‘channel’ (McGuire, 1969a, p. 172) by manipulating confidence kinesically, i.e. via body language. Although body-language variables have been increasingly researched in recent years (for recent reviews, see Duncan, 1969; Mehrabian, 1969), few studies (cf. Mehrabian & Williams, 1969) have directly investigated the persuasiveness of kinesic cues. If the amount of confidence expressed kinesically is varied while other elements of an argument are held constant, and if the confidently expressed argument is more persuasive, then we will have demonstrated a second channel by means of which expressed confidence can operate.

STUDY I

Method Subiects

participated in the study immediately prior to a club meeting.

Procedure Subjects took part individually in a ‘jury study’. Subjects were administered booklets

containing the facts of a law case, instructions to the jury, an argument purported to be that of ‘a student interviewed in a previous study’, verdict sheets and, finally, a page on which the subjects were asked to describe their impression of the student whose argument they had read. Subjects read the materials in the booklet and registered their verdicts and impressions.

Communications Booklets contained the same fact summary and judge’s instructions used previously

(London et aZ., xg7oc). Written especially for the present study was the ‘student’s argument’ in favour of finding the defendant, Brooks Airlines, not liable.

The subjects were 52 undergraduate women. They were members of a social club and

236 CATHA MASLOW, KATHRYN YOSELSON AND HARVEY LONDON

Student’s argument. There were two versions of the argument for finding the defendant not liable. Both versions made the same points in favour of the defendant. However, the argument was structured so that there were ‘slots’ into which expressions of confidence or doubt could be placed. These expressions were drawn from the scoring manual mentioned above (Yoselson et al., 1970). One half of the subjects, randomly chosen, received the argument containing the confidence expressions ; the other half received the argument containing the doubt expressions. The tone of the arguments so constructed did not differ from the tone of arguments used by ‘real’ persuaders and persuadees (cf. Johnson & London, 1968; London et al., 1970~) .

The argument is reproduced below. It was written colloquially, and was presented to the subjects as if it were a transcript of an interview with a student. Pairs of expressions in parentheses are the aforementioned expressions of confidence and doubt. For each pair, the first would be placed closer to the ‘extreme confidence’ end of a continuum running from confidence to doubt. A reading of the two separate versions of the argument will reveal that while in both the student reaches the same conclusions for the same reasons on each point, the expressions in the doubtful version suggest that the student is wavering before he reaches each conclusion.

‘(Obviously, I don’t know) my first (concern, conflict) is deciding what to base liability on. I mean, we were given only the facts, so I have to (reason, wonder) what the law must say about this. (I believe, I’m not positive) that causation is the best basis for judging whether someone should pay damages. Looking at it (logically, all kinds of ways) the (clarity, ambiguity) of the meaning of causation is (evident, confusing) to me. I would say with (assurance, hesitation) that the cause of any damage is that without which the damage would not have occurred.

‘Another (point, question) I’m quite (sure, unsure) about is the mechanic’s negligence. (I feel, I’m not sure) it’s irrelevant. I would say with some (confidence, doubt) that the case should be based solely on causation . . . [pause].

‘ If Brooks Airline Company’s liability depends on causation, this case rests on whether or not the damage would have occurred even if the plane hadn’t crashed. (I am certain, My problem is) that you can’t know whether the natural fire would have caused Ames Lumber Company’s loss whether or not the plane had crashed. Since either fire may have caused the damage (it’s obvious to me, I’m leaning both ways), (you can’t assume that, I don’t know if) the plane fire caused the damage. (I’m satisfied, I’m unsure) that there’s only one fair verdict. In fact, my verdict (is determined, could go either way). I’ll have to base it on this, that (it’s clear, I admit) that you can’t assume that Brooks Airline Company is the cause of the damage. Therefore, I (maintain, grant) that we can’t hold them liable for Ames Lumber Company’s loss’.

Measurement of persuasion Persuasion was assessed by the extent of the subject’s agreement with the hypothetical

student that Brooks Airlines, the defendant, should not be held liable for the plaintiff’s damage. Subjects were asked to indicate on the verdict sheets immediately following the substantive material (u) percentage confidence (from o to 100) that Brooks should not be held liable; (b) percentage doubt (also from o to 100) that Brooks should not be held liable.

IRESULTS EfJectiveness of manipulation

T o test whether expressed confidence was effectively manipulated, Thurstone’s paired comparison technique (Edwards, 1957) was utilized. Five female college students, paid volunteers, were recruited from Boston University’s summer school introductory psychology class. These students were tested simultaneously. They were given booklets containing instructions and both versions of the student’s argument. In three of the booklets, the confidently expressed argument was placed first; in two of the booklets, the doubtfully expressed argument was placed first. The girls were assigned booklets at random and were asked to indicate on a rating

Persuasiveness of Confidence 237 sheet which of the versions of the argument expressed more confidence in the points presented. All five girls rated the version postulated to express more confidence as the more confident. The P value associated with this result is 0-031.* This P value indicates that the expression of confidence was effectively manipulated.

Efect of linguistically expressed confidence on persumion The hypothesis advanced was that subjects receiving the confidently expressed

argument would be significantly more persuaded than subjects receiving the doubt- fully expressed argument.

To obtain an overall index of confidence that Brooks should not be held liable, we simply subtracted a subject’s percentage of doubt from his percentage of confidence.+ Subjects receiving the confident argument had a mean confidence index of 44’0 that Brooks should not be held liable. Subjects receiving the doubtful argument had a mean confidence index of 10.3. A t test of the difference between these means yielded P -= 0.05. Subjects receiving the confident argument were significantly more persuaded that Brooks Airlines should not be held liable.

STUDY 2

Method Subjects

The subjects were 69 undergraduate females, all of whom were paid volunteers.

Manipulation of kinesically expressed confidence A professional actor was hired to play a law student presenting his views about a case.

The actor, dressed conservatively and seated at a n executive-sized desk cluttered with papers and books, was filmed using a Sony videotape camera and a Sony videocorder. The camera rested on a table, about 7 ft. away from the actor.

Before filming, the actor tape-recorded a ‘discussion’ of the case. The discussion consisted of the argument used in Study I but written ‘neutrally’, i.e. with confidence and doubt words deleted and other words inserted appropriately. The tape-recorded discussion allowed control of language (words) and para-language (tone of voice, rate of speech, etc.) across conditions insofar as the discussion waa ‘dubbed’ into all three videotapes used in this study. The tape discussion also facilitated control of the length of videotapes at I min. 10 sec.

Three separate videotapes were prepared. For one, the actor was asked to ‘discuss’ the case in a confident manner, for the second, in a doubtful manner, and for the third, ‘neutrally’, i.e. midway between confidence and doubt. In none of the three videotape sessions did the actor actually speak. Rather, he coordinated his mouth movements to coincide with his words on the previously recorded sound tape, which was played during filming. Later, pretesting indicated that the subjects were unaware that the actor was simply mouthing the words he appeared to be uttering.

Procedure The experimenter scheduled the subjects for experimental sessions by circulating sign-up

sheets. In all, six sessions were conducted, two per experimental condition. Twenty-four subjects were run in the confidence condition, 20 were run in the neutral condition, and 25 were run in the doubt condition.

At each session, the subjects were seated and asked to make sure they had a full view of a Sony television monitor which was placed on a high desk in the front of the room. The experimenter then explained that the point of the study was to help evaluate the ability of

* All P values reported in this paper are two-tailed. i- This mode of combining response scales to yield a more sensitive index is suggested

in Schachter & Singer (1962, p. 389). It should be noted that the two components of the index each yield results completely consistent with those obtained by the use of the index.

238 CATHA MASLOW, KATHRYN YOSELSON AND HARVEY LONDON law students to work in legal clinics. The subjects were asked to play the role of jury members in a law case. They were to read the facts of a law case and judge’s instructions to the jury, and then to observe a videotape with comments on the case by a high-ranking law student. They were told finally that their individual verdicts would be solicited after they had viewed the tape.

While subjects were reading the background materials, precisely the same as those used in Study I, the experimenter chose a slip of paper from an envelope in order to determine which of the three tapes would be shown.

After the film the subjects indicated their verdicts, thus providing the experimenter with a measure of persuasion, and filled out a post-experimental questionnaire.

Finally, the experimenter collected all materials, gave the subjects further information about the study, thanked the subjects for their participation, and paid them.

RESULTS Efectiveness of manipulation

To test whether expressed confidence was effectively manipulated, Thurstone’s paired comparison technique was again utilized. Ten female high school students, paid volunteers, were recruited. These students were tested one at a time and were asked to indicate on a rating sheet for all possible pairs of the three videotapes, which tape of each pair expressed more confidence in the points presented. The order of pairs and the order of tapes within each pair were randomized using an appropriate procedure.

The resulting data were analysed to yield the following scale values: doubtful tape, 0.00; neutral tape, 2-92; confident tape, 3-27. These values are in line with expectations. Further Mosteller’s (195 I) test of significance for paired comparisons indicated (0.50 < P -= 0.70) that the assumptions involved in using the method of paired comparisons are tenable for the given data.

Eflect of expressed confidence on persuasion As in Study I, persuasion was assessed via the extent of subject’s agreement with

the speaker, i.e. subject’s overall confidence that Brooks Airlines should not be held liable. From the data on the subject’s verdict sheet, confidence indices were constructed by subtracting the subject’s percentage confidence that Brooks should be held liable from her percentage confidence that Brooks should not be held liable. Mean indices ran from a low of 7 in the doubt condition to a high of 46.9 in the confidence condition. Analysis of variance indicated that confidence indices differed as a function of experimental condition (F = 3.66; d.f. = 2, 66; P < 0’05). Fitting appropriate coefficients to determine the significance of the linear component of the between-condition sum of squares yielded F = 7-3, d.f. = I, 66, P -= 0.01. Subjects were increasingly persuaded as a function of increasingly kinesically expressed confidence.

DISCUSSION The results support both hypotheses and allow us to begin building a ‘structure’ using McGuire’s (1969a, p. 172) terminology: a source is increasingly persuasive as his message increases in confidence whether expressed over linguistic or kinesic channels. Putting the data in this way immediately suggests a third possible channel for expressing confidence-the paralinguistic. Persumably, the relation between

Persuasiveness of ConJidence 239 paralinguistically expressed confidence and persuasion would parallel the findings of the present report.

However, knowledge of within-channel relationships does not necessarily allow us to determine what will occur when expressed confidence is varied in two or more channels simultaneously. The most obvious prediction is that effects will simply summate, but there are other possibilities. For instance, a person who expresses much confidence over one channel and much doubt over another might appear odd and thus be less persuasive than another person who expresses intermediate con- fidence over both channels, even though both people express the same ‘net’ confidence.

In any event, the channel notion does have validity for distinguishing between the various modes by means of which confidence may be expressed. At the same time, Study 2 highlights a peculiarity of the source/message distinction. We conceptualized our manipulations in both Studies I and 2 as of attributes of the message. Yet, in Study 2 at least, we could hardly have manipulated kinesically expressed confidence without ourselves operationally manipulating the source. Perhaps what this shows is that certain variables, e.g. expressed confidence, are message attributes only for certain theoretical purposes and that, for other purposes, they must be conceived to be attributes of the source as well.

As a final point we note that the results of Study 2 raise the question of differences in the actor’s behaviour across conditions. We do not provide an analysis of differ- ences here, since the focus of Study 2 was simply to establish the existence of a non-verbal channel for the expression of confidence; to go into the details of the kinesic cues involved would disproportionately weight the paper in this respect. Such an analysis, however, is an obvious next step.

This research was supported by N.I.M.H. grant 2T0zMH-077o1-06 and by N.I.H. grant 7044-04. We thank Fred Grandy who played the law student in Study 2 and Michael Grinberg who aided in data analysis.

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CATHA MASLOW, KATHRYN YOSELSON AND HARVEY LONDON

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Manuscript received 8J.m 1970

Revised manuscript received I I December 1970