Embodiment of Approach Motivation 1 The Embodiment of Approach Motivation

One of the most fundamental and important aspects of motivation is the urge to approach, which is manifest in its most basic form by moving toward (Harmon-Jones, Harmon-Jones, & Price, in press). Although much research has examined cognitive influences on approach motivation, less research has examined bodily influences. In this chapter (talk), we will present the results of a program of research that has examined how body posture influences approach motivation. The research has manipulated approach motivation from low to high intensity by placing participants in a supine vs. leaning forward posture, respectively. In the presence of approach-related stimuli, leaning forward enhances approach responses, whereas lying down reduces these responses. These bodily manipulations influence a number of responses associated with approach motivation, including simple reflexes, early visual cortical activations, asymmetric frontal cortical activations, and cognitive responses. These results illuminate the role of the body in motivational processes, as they show that approach motivation is partially dependent on the action-readiness of the body. Embodiment of Approach Motivation 3 Emotion and motivation are fundamental to movement. This idea is not only captured in scientific research on emotion and motivation but also reflected in the English language. The word "emotion" is derived from the French word "émouvoir," which is based on the Latin word "emovere," where e(variant of ex-) means 'out' and movere means 'move'. The word "motivation" is also derived from "movere." Thus, the meaning of the English words, emotion and motivation, are derived from words that mean to move and movement requires the body for its enactment or expression. Often, laypersons and scientists alike conceive of our perceptions or cognitions of psychobiologically significant stimuli as the sole cause of our motivational states. But is this accurate? Is motivation fundamentally traced back to only our perceptions or cognitions of stimuli? Or might our actions or behaviours influence our motivational states? Although evidence exists supporting the idea that facial expressions influence emotional experience, far less evidence has tested whether bodily movement influences motivation, even non-conscious aspects of motivation. In this chapter, we review a program of research that provides support for the notion that that body posture influences motivation even at non-conscious levels. Brief Review of Influence of Facial and Bodily Expressions on Emotive States The majority of research on the role of bodily expressions influencing processes related to motivation comes from work on facial expressions and emotions. The idea that facial expressions are closely connected with emotions was recognized over 100 years ago by Darwin (1872) and James (1890). Building upon these ideas, Laird (1974) proposed the facial feedback hypothesis that posited that manipulated facial expressions of emotion cause changes in emotional feelings (for a review, see Adelmann & Zajonc, 1989). This hypothesis is typically tested by manipulating participants’ facial expressions with specific muscle configuration instructions or through non-obtrusive methods. For Embodiment of Approach Motivation 4 example, participants have been induced to hold a pen between their teeth to facilitate smiling or to hold a pen with their lips to inhibit smiling (Strack, Martin, & Stepper, 1988). Once the facial expression manipulation is in place, participants will be presented with a stimulus and instructed to give their emotional reactions to the stimulus. Experiments such as these have revealed that when smiling is facilitated as compared to inhibited, participants respond more positively to cartoons (Strack et al., 1988). Other methods have revealed conceptually consistent results. For instance, when the responsiveness of individuals’ facial muscles has been reduced by administration of botulinum toxin-A (BTX), individuals are slower at reading of emotional passages (Havas, Glenberg, Gutowski, Lucarelli, & Davidson, 2010) and have decreased amygdala activation during intentional facial mimicry (Hennenlotter et al., 2009). Zajonc and colleagues proposed that one mechanism by which facial expressions may influence emotional feelings is that the movement of facial muscles influences other physiological processes (Zajonc, Murphy, & Inglehart, 1989). Zajonc et al. (1989) posited that the furrowing of the brow (i.e., the downward movement of the corrugator supercilii muscle) that often occurs during expressions of negative emotions such as anger might reduce air-intake into the nasal cavity, cause more mouthas compared to nose-breathing, and raise the temperature of blood entering the brain. This rise in facial temperature would cause the experience of negative affect. In contrast, activation of the muscles involved in smiling (i.e., contraction of the zygomatic major muscle) should open the nasal cavity, improve nose breathing, and reduce the temperature of blood entering the brain. This reduction in facial temperature due to smiling would cause the experience of positive affect. These predictions were based on the idea that thermoregulation of brain areas such as the hypothalamus could influence hedonic states and associated neurotransmitter (e.g., norepinephrine) activity. Embodiment of Approach Motivation 5 Zajonc and colleagues (1989) tested these ideas by having participants recite sounds that caused greater or lesser brow furrowing, and found that greater brow furrowing caused higher facial temperatures and more negative evaluations of information. In addition, they found that when cool air was infused into participants’ nasal cavities, they had reduced overall facial temperature. Subsequent research directly manipulated hypothalamic cooling vs. heating in rats, and found that cooling caused more eating but not more hedonic reactions to taste. Zajonc and colleagues suggested that hypothalamic cooling may increase the attractiveness of the food without modulating taste pleasure (Berridge & Zajonc, 2001). These results suggest that facial expressions influence thermoregulation of the hypothalamus which, subsequently, influences an organism’s emotional state. Other mechanisms for the facial feedback responses have been suggested. One is that facial expressions of emotion cause innate, parallel physiological changes in heart rate, skin conductance, and other measures of autonomic nervous system activity (Ekman, Levenson, & Friesen, 1983). Levenson, Ekman, and Friesen (1990) instructed participants to move individual facial muscles to form facial expressions of discrete emotions such as anger and fear. Once the facial expressions were fully created, participants’ heart rate, skin conductance, finger temperature, and forearm muscle tension were recorded. Over several experiments, Levenson et al. (1990) found that facial expressions of discrete emotions caused discrete patterns of autonomic nervous system activity. For example, facial expressions of anger, sadness, or fear caused greater heart rate acceleration than that found with the expression of disgust. Facial expressions of anger caused higher finger temperature than expressions of fear. Subsequent studies replicated these original results, which were obtained with American samples, with men of the Minangkabau from West Sumatra (Levenson, Ekman, Heider, & Friesen, 1992). Embodiment of Approach Motivation 6 Taken together, these results suggest that facial expressions have direct effects on thermoregulation of certain brain structures and autonomic nervous system activity. But how does the brain/body transform these signals into subjective emotional states? Some researchers have proposed that projections from the brainstem, which carries sympathetic and parasympathetic bodily signals, to nuclei within the anterior insular cortex and the anterior cingulate cortex are involved in this process (for a review, see Craig, 2002, 2009). Another critical region in these processes is the somatosensory cortex (Damasio, 1993). Although the majority of research has focused on manipulations of facial expressions of emotions, other bodily manipulations have been used in a few studies. For instance, some studies have found that when individuals nod their heads up and down, as compared to shake their heads from side to side, they have more positive attitudes toward neutral stimuli (Tom, Pettersen, Lay, Burton, & Cook, 1991) and are more likely to agree with persuasive messages (Wells & Petty, 1981). Other research has found that flexing the arm, a movement associated with acquiring desired stimuli, causes individuals to form more positive attitudes toward neutral stimuli. In contrast, extending the arm, a movement associated with avoiding undesirable stimuli, causes individuals to form more negative attitudes toward neutral stimuli (Cacioppo, Priester, & Berntson, 1993). Subsequent research has found that the positivity/negativity of the stimuli can influence these arm-flexion and arm-extension effects (Centerbar & Clore, 2006). Moreover, the meaning attributed to these types of motor actions is also an important factor (Eder & Rothermund, 2008). Brief Review of Asymmetric Frontal Cortical Activity and Emotive States One neural variable that has received considerable attention is asymmetric frontal cortical activity. Observational studies dating back to the 1930s suggested that damage to the Embodiment of Approach Motivation 7 left versus right frontal cortex yielded very different emotive consequences. That is, damage to the right frontal region is associated with the onset of mania symptoms (Starkstein, Boston, & Robinson, 1988). In contrast, damage to the left frontal region (Robinson, Boston, Starkstein, & Price, 1988) is associated with depression symptoms. One interpretation of this research is that lesions to the left frontal region reduce or eliminate the organism’s capability to experience and express positive affect and/or approach motivation. The converse would be the case for the right frontal region. Another interpretation is that with the left frontal region’s functioning reduced or eliminated, the right frontal region’s functioning is over-expressed and thus more negative affect (e.g., depression) is presented, and vice versa. This latter interpretation assumes there is a reciprocal connection between activities in the left versus right frontal cortical regions, such that when one hemisphere is taken off-line, the other becomes over-active. The emotive functions of asymmetric frontal cortical activity have been tested with a host of neuroscience techniques, including functional magnetic resonance imagining (Berkman & Lieberman, 2010), event-related brain potentials (Cunningham et al., 2004), repetitive transcranial magnetic stimulation (van Honk & Schutter, 2007), transcranial direct current stimulation (Hortensius, Schutter, & Harmon-Jones, 2012; Kelley, Hortensius, & Harmon-Jones, in press), and electroencephalographic (EEG) recordings (Harmon-Jones, 2003; Harmon-Jones, Gable, & Peterson, 2010). In this body of research, relative right frontal activity has been associated with withdrawal-oriented emotions, such as fear and disgust (Davidson, Ekman, Saron, Senulis, & Friesen, 1990; Jones & Fox, 1992), and relative left frontal activity has been associated with approach-oriented emotions, such as joy (Davidson & Fox, 1982) and anger (Harmon-Jones, 2004; Harmon-Jones & Allen 1998; Harmon-Jones & Sigelman, 2001; Harmon-Jones, Vaughn-Scott, Mohr, Sigelman, & Harmon-Jones, 2004; Embodiment of Approach Motivation 8 Verona, Sadeh, & Curtin, 2009). Research has also been conducted with bodily manipulations to further test the emotive functions of asymmetric frontal cortical activity. The Influence of Facial Expressions and Unilateral Body Movements on Asymmetric Frontal Cortical Activity and Approach Motivation