The link between our mind and our bodily responses has long been studied by persuasion researchers. It goes back to the use of the term "attitude" to refer to the posture of one’s body (Galton, 1884), and to the notion that attitudes may reflect—and be influenced by—expressive motor behaviors (e.g., a scowling face can indicate a hostile attitude; Darwin, 1872). Colloquially, it is common to refer to an attitude as an individual’s position on an issue, although the meaning in this case refers to an evaluative, rather than a physical, orientation.
The main idea behind the concept of embodied persuasion is that people’s own behaviors can impact their attitudes (their likes and dislikes). Indeed, when we smile, we tend to be happier than when we frown, and see everything with a positive light. Also, when we nod our heads we tend to like things better than when we shake our heads. For example, in a classic study, individuals who were induced to nod their heads (i.e., agreement behavior) while listening to a persuasive message were more favorable to the proposal than people who were induced to shake their heads (i.e., disagreement behavior) while listening to the same message (Wells & Petty, 1980). Other research has found that information presented while performing an approach behavior (e.g., using one’s hands to pull up from underneath a table) is evaluated more positively than information presented during an avoidance behavior (e.g., pushing down on a table top surface; Cacioppo, Priester, & Berntson, 1993). Similar findings have been found for a large number of behaviors, postures, and body movements (for a review, Briñol & Petty, 2008).
Although the ability of bodily movements to influence attitudes seems to be a well-established phenomenon, most research on this topic has not focused on the psychological mechanisms by which the body affects attitudes. Understanding these processes is essential in order to predict whether, when, and how attitudes will change, as well as to predict whether, when, and how attitudes will result in further behavioral changes. That is, although we might like something more when we smile (vs. frown) or when we nod our heads (vs. shake), it is important to understand the processes responsible for these changes in evaluation. It might be that agreement behaviors such as smiling and nodding make us think about everything in a positive light, or it might be that they encourage us not to think much about the information we receive.
Because these (and other) mental operations are very different, Richard Petty and I have organized the literature on embodied persuasion around the basic mechanisms by which the body can influence our attitudes. The psychological processes relevant to attitude change can be organized into a finite set. A person’s bodily movements or responses, like other variables in persuasion settings, can influence attitudes by affecting one or more of these underlying processes: (a) serving as simple peripheral cues to change, (b) affecting the amount of issue-relevant thinking that occurs, (c) producing a bias to the thoughts that come to mind, and (d) affecting structural properties of the thoughts (e.g., thought confidence). Among other things, identifying the processes by which bodily movements affect attitudes is informative about the immediate and long-term consequences of persuasion.
Bodily Responses Serve as Simple Cues to Persuasion
Our body posture, our facial expressions, and the way we movecan all influence our opinions in very subtle ways. In fact, because bodily responses belong to our physical nature, researchers tend to think that they have to operate in our mind through very simple, automatic mechanisms. However, the body can influence our attitudes by processes that require both low and high degrees of cognitive effort. Under low-effort conditions, our actions can influence our opinions on a topic even when we do not think about the information we receive. The body is likely to serve as a simple cue when motivation and ability to think are constrained. For example, Cacioppo, et al. (1993) observed that neutral Chinese ideographs (irrelevant stimuli for the sample of participants) presented during arm flexion were subsequently evaluated more favorably than ideographs presented during arm extension. In another line of research, Strack, Martin, and Stepper (1988) asked participants to either hold a pen between their teeth (which facilitates a facial expression similar to smiling) or to hold a pen between their lips (which inhibits smiling) while watching cartoons. Although participants did not recognize the meaning of their facial expressions, they judged the cartoons to be funnier in the former condition than in the latter.
Aside from using mere associations such as those described above, people can also rely on simple heuristics when forming or changing attitudes. For instance, people can draw direct inferences about their attitudes based on their body states (e.g., if my heart is beating fast, I must like this object; Valins, 1966). Moreover, in the domain of emotions, people induced to gaze into each others’ eyes reported feeling romantically attracted to one another (Kellerman, Lewis, & Laird, 1989), and when induced to slump in their chairs, people feel diminished pride in their task performance (Stepper & Strack, 1993).
Bodily Responses Influence the Amount of Thinking
Our body can also make us think about things to a greater or lesser degree. Our postures, facial expressions, and movements sometimes distract us from what is going on, but at other times those same actions can help us to think about things. That is, bodily responses affect the amount of thinking a person does. For example, because certain actions make people feel pleasant and secure, a person might think less about what is going on when smiling than when frowning, or when nodding than when shaking. The body affects the amount of thinking particularly when the person has not really decided whether think carefully about something (i.e., when deciding whether to think or not to think). In an early demonstration that body posture can affect susceptibility to a persuasive communication by affecting the extent of thinking, Petty, Wells, Heesacker, Brock, and Cacioppo(1983) asked undergraduate students to try new headphones to rate their qualities. Some participants were then told to stand while testing the headphones, whereas others were told to lie down while listening to a persuasive proposal. Consistent with the idea that posture can affect thinking, this study showed that while reclining participants were differentially persuaded by the strong and weak arguments (suggesting that they paid careful attention to the message), standing participants were not.
Important practical implications flow from the possibility that body manipulations can induce persuasion by affecting the amount of thinking the individual engages in. For example, the practice of brainwashing often involves a massive assault on the body, in which the victim is frequently starved, drugged, tortured, and emotionally agitated. In other domains, attempts at persuasion may involve the direct control of a person’s behavior, including alteration in appearance (e.g., clothing, posture, hairstyle), public behaviors (e.g., self-criticism), and escalation of commitment, in which a recruit is asked, over time, to engage in increasingly costly behaviors that are hard to undo (e.g., donating one’s personal possessions to the group, or recruiting new members). The combination of physical deprivation and behavior modification has been argued to reduce a person’s motivation and ability to think, thus rendering that person more susceptible to what would ordinarily have been weak arguments (e.g., faulty logic, incomplete verification, erroneous and stereotypical information; for a review, see, Baron, 2000). These simplistic, weak messages could presumably be easily counter-argued if people were not so physically depleted (e.g., Wheeler, Briñol, & Hermman, 2007).
Bodily Responses Influence the Direction of Thinking
Our bodies can influence persuasion not only by affecting the amount of thinking but also by affecting the direction of that thinking. Obviously, for the body to influence thoughts, people need to be thinking. One extensively explored idea is that bodily responses can shape attitudes by affecting the valence (i.e., positivity or negativity) of the thoughts that come to mind when thinking about an attitude object. For example, in the original research on head movements and persuasion, Wells and Petty(1980) speculated that previous experience had made nodding compatible with “approval” and favorable thinking, whereas head shaking was more compatible with “disapproval” and unfavorable thinking. In line with the Wells and Petty proposal about behavior biasing thinking, Neumann, Förster, and Strack (2000) argued that overt behavior can directly trigger compatible thoughts that facilitate encoding and processing of evaluatively congruent information.
Bodily Responses Influence Thought-Confidence
So far, we have seen how the body can influence attitudes by serving as a simple cue and by affecting either the amount or direction of thinking. Recently, Richard Petty and I have proposed that behavior can not only influence what people think about things, but can also impact what people think about their thoughts (i.e., meta-cognition). This idea is referred to as the self-validation hypothesis (Petty, Briñol & Tormala, 2002). The key notion is that generating thoughts is not sufficient for these thoughts to have an impact on judgments. Rather, one must also have confidence in one’s thoughts. Our self-validation view argues that the confidence that emerges from behavior can magnify the effect of anything that is currently available in people’s minds, including not only their thoughts about a persuasive message, but also other cognitions, emotions, goals, and so forth. That is, confidence applies to whatever mental contents are salient and available at the time (see Briñol & Petty, 2009, for a review).
Consider the research on head nodding described earlier, which had assumed that nodding one’s head in a vertical (versus horizontal) manner produced more positive attitudes either because vertical head nodding biased thinking in a favorable direction or because head nodding served as a relatively simple affective cue. The self-validation hypothesis suggests another possibility. Specifically, this hypothesis suggests that just as vertical head movements from others give us confidence in what we are saying, our own vertical head movements could give us confidence in what we are thinking. In a series of studies, we (Briñol & Petty, 2003) found that head movements affected the confidence people had in their thoughts and thereby had an impact on attitudes. Thus, when people listened through head phones to strong arguments advocating that students be required to carry personal identification cards on campus, vertical movements led to more favorable attitudes than horizontal movements, as would be expected if vertical movements increased confidence in one’s favorable thoughts. However, when people listened to weak arguments in favor of the identification cards, vertical movements led to less favorable attitudes than horizontal movements, as would be expected if vertical movements increased confidence in one’s negative thoughts.
In a different exploration of this possibility (Briñol & Petty, 2003, Experiment 4), we asked participants, as part of a presumed graphology study, to think about and write down their best or worse qualities (i.e., thought-direction manipulation) using their dominant or non-dominant hands (i.e., overt behavior manipulation). Then, participants rated the confidence in the thoughts they listed and reported their self-esteem. Since writing with the non-dominant hand happens infrequently and is very difficult, and because whatever is written with the non-dominant may appear "shaky," we expected and found that using the non-dominant hand decreased the confidence with which people held the thoughts they had listed. As a consequence, the effect of the direction of thoughts (i.e., positive vs. negative) on state self-esteem was significantly greater when participants wrote their thoughts with their dominant hand than with their non-dominant hand. That is, writing positive thoughts about oneself with the dominant hand increased self-esteem relative to writing positive thoughts with the non-dominant hand, but writing negative thoughts with the dominant hand resulted in the reverse pattern. When writing about the things we do not like about ourselves, we feel better if we use the non-dominant (vs. dominant) hand. This is interesting because it reveals that people do not feel too badly about themselves, even though they have just listed negative self-relevant thoughts in objectively unattractive handwriting. More recently, Briñol, Petty, and Wagner (2009) found similar results when participants had to write their qualities while they were sitting with their back erect, pushing their chest out (confident posture) or slouched forward with their back curved (doubt posture). For body actions to influence thought confidence, people have to have thoughts to begin with, and also think about them.
Final Remarks
This review has described the various ways in which bodily movements and overt behaviors can affect our likes and dislikes. Importantly, the conditions necessary for each of these fundamental processes have also been specified (e.g., behavior produces its effects by simple processes when people do not think, but behavior affects the direction of the thoughts when people do think). Although a large number of behaviors, from simple to complex, have been examined in persuasion research, many other behaviors remain unexamined. As noted by Lakoff and Johnson (1999), language is replete with metaphors related to the body, many of which could be informative in this regard. For example, evaluation can be linked to dimensions such as distance (e.g., good is close: "I would like to get closer to or approach what I like”) and space (e.g., good is often up: “I am feeling up today"). In addition to these spatial parameters, metaphorical evidence often associates evaluation with other dimensions, such as brightness (e.g., dark is bad), smell (e.g., bad is often stinky: "this movie stinks"), size (e.g., important is big: “tomorrow is a big day”), temperature (e.g., good is warmth: "she is hot"), and weight (e.g., bad is heavy:"“she is weighed down by responsibilities"). Additionally, metaphors related to change (e.g., change is motion "my car has gone from bad to worse lately"), and thinking (e.g., knowing is seeing, "I see what you mean"; understanding is grasping, "I have never been able to grasp numbers") could be equally informative in the domain of embodied persuasion.
Second, most of the behaviors used in the experiments described in this article have very clear meanings attached to them (e.g., nodding is associated with agreement). However, the meaning of behaviors can vary among individuals and situations. For example, nodding can be associated with disagreement in certain contexts (e.g., "yea-yea" responding), and arm extension can be seen as approaching in some settings (e.g., extending the arm to reach a desired object). We argue that if the meaning associated with a behavior changes, the effect of that behavior on subsequent attitudes could also change.
Third, people can not only differ with respect to the meanings associated with behaviors, but can also differ with respect to a wide variety of factors potentially relevant to embodiment. For example, people can vary in the extent to which they attend to and use their behavior in defining their attitudes.
Fourth, it might not be necessary to physically act for behavior to produce attitude change. Indeed, merely believing that a behavior occurred, reminding oneself of past behaviors, imaging future behaviors, or observing the behaviors of others can often produce effects similar to those obtained from actual motor behavior.
Fifth, although it is relatively easy to provide cover stories or to ask participants in experimental settings to act in a given way, it is not so easy to do so in more naturalistic conditions. One way to do this involves acting in the desired way, thus producing mimicry in message recipients. If someone smiles or nods his or her head at you, you are likely to smile and nod back.
Finally, it might be helpful for some people to know that their actions can influence their likes and dislikes. In fact, our bodies can provide us with valuable information in many cases (e.g., elevated heart rate and stomach butterflies when encountering a person informs us that we like that person). However, if people believe that their judgments are somehow being biased or influenced by their bodily actions and do not want this to occur, they may adjust their judgments in a direction opposite to the expected bias (correction processes; Wegener & Petty, 1997). As is the case with other meta-cognitive processes described in this article, such correction processes require extensive thinking to operate.
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