The impact of rewards on empathic accuracy and emotional mimicry

Transcription

1 DOI 1.17/s ORIGINAL PAPER The impact of rewards on empathic accuracy and emotional mimicry Ursula Hess 1 Christophe Blaison 1 Stéphane Dandeneau 2 Springer Science+Business Media New York 216 Abstract The notion that motivation influences empathic accuracy has been inferred from aspects of the task, the situation or the relationship between interaction partners or between groups. The present research assessed whether monetary reward influences cognitive and affective empathy. In Study 1, cognitive empathy was assessed for 42 participants who decoded briefly (33 ms) presented expressions of sadness and anger. For half the participants, correctly decoded expressions on male faces were rewarded, for the other half correctly decoded expressions on female faces were rewarded. The results showed that rewards increase empathic accuracy for both emotions equally. In Study 2, facial EMG was measured as well to assess emotional mimicry as an index of affective empathy. Study 2 replicated the findings from Study 1 and found a moderation of affective empathy as indexed through facial mimicry for sadness. Thus, simple monetary rewards affect both cognitive and affective empathy. Keywords Emotion recognition Reward Empathy Mimicry Introduction Emotions are pervasive in everyday life and one of the skills that greatly helps us navigate and negotiate our social environment is the recognition of others emotions (Niedenthal and Brauer 212). Hence it is not surprising that emotion & Ursula Hess Ursula.Hess@hu-berlin.de 1 2 Department of Psychology, Humboldt-Universität zu, Berlin, Germany Université du Québec à Montréal, Montreal, Canada recognition has been studied intensely over the past 1 years. In this context, both situational and individual difference factors that can influence emotion recognition have been studied (see e.g., Hess and Thibault 29 for an overview). The ability to understand and respond to the emotional messages of others is usually referred to as empathy (Decety and Jackson 26) and is commonly divided into two processes (Lamm et al. 27): (1) cognitive empathy, the ability to accurately infer another person s feelings (e.g., Ickes 1997) and (2) affective empathy, a process where the perception of another s emotional state generates a matching reaction in the perceiver (e.g., de Waal 28). One factor suggested to explain differences in cognitive empathy is the perceiver s motivation. Yet, to our knowledge this assumption has not been tested directly. Rather, motivation has been inferred from the aspects of the task, the situation (for example, presence of threat) or aspects of the relationship between interactions partners (see Ickes and Simpson 24 for an overview) or between groups (Thibault et al. 26). A more direct approach to manipulating motivation is to provide a monetary incentive. In fact, in humans the nucleus accumbens, a brain region associated with cognitive processing of motivation, pleasure, and reward, is activated by the mere anticipation of a monetary reward (Knutson et al. 21). The present research therefore proposes to test the motivational hypothesis by investigating the effect of a monetary reward on both the cognitive component (Study 1) and the affective component (Study 2) of empathy. In both studies we assessed emotion recognition accuracy as an index of cognitive empathy. In Study 2, we assessed facial mimicry, the tendency to imitate facially the people with whom we are interacting (e.g., Dimberg 1982; Hess and Fischer 213) as an measure of affective empathy. Mimicry is an important aspect of empathic responding (Lamm et al.

2 28) and is understood as a part of the empathic process (e.g., Singer and Lamm 29; Walter 212). Further, it has been shown that participants respond with more mimicry to happy faces that were positively conditioned in a prior task (Sims et al. 212), that is, they reacted to an implicit reward. Yet, in this case the difference in mimicry may be due to differential liking of the stimulus which is an established moderator of mimicry (Likowski et al. 28). In the current studies, we manipulated explicit motivation by promising participants a monetary reward as a function of their decoding accuracy. Specifically, participants were promised a reward for the decoding of one type of face stimulus but not for another. However, for reward to have an effect the task can not be too easy (as then we would be faced with a ceiling effect) nor should the task be so difficult that it is discouraging and results in a floor effect. Also, for Study 2, it was important that the presentation time allows for mimicry reactions. We therefore presented sad and angry facial expressions for 33 ms (without mask) and asked participants to indicate whether the expression showed anger or sadness. This presentation format is supraliminal but very brief and was chosen to render the task more difficult, without however, arriving at a floor effect. We also chose anger and sadness because they share several expressive elements (closed mouth, drawing of the eyebrows together) making the distinction non trivial, thus adding to creating a task that is challenging but not discouragingly difficult. For Study 1, we predicted that participants would show higher accuracy rates for rewarded types of faces than for unrewarded ones. Study 2 followed similar reward/no reward procedure, while facial mimicry was assessed as an index of affective empathy. We predicted more mimicry in addition to higher decoding accuracy for rewarded than for unrewarded faces. Thus, we predicted that monetary reward would increase participants motivation to be accurate which would in turn affect both cognitive and affective empathy. Study 1 Method Participants A total of 42 participants (23 men) with a mean age of 26 (SD 5.3) years participated individually. They received 8 plus the reward ( 2; see below) for their participation. Stimulus material Expressions of anger and sadness of 9 men and 9 women were taken from the NimStim set of emotional facial expressions (Tottenham et al. 29). This resulted in a total of 2 (gender) 9 2 (emotion expression) 9 9 (individuals) = 36 Stimuli, which were presented in random order. Procedure Following a 3 ms presentation of a fixation cross an emotional facial expression was shown for 33 ms, unmasked. Participants were instructed to indicate as fast as possible, using the D and K keys on the keyboard, whether the expression was sad or angry. Key assignments were counterbalanced across subjects. Participants received feedback on their performance. The feedback was shown for 5 ms and consisted of a green dollar sign for rewarded trials that were correct and of two red letters X for rewarded trials that were incorrect. Green and red hash marks signaled correct and incorrect unrewarded trials. That is, participants received contingent feedback on all trials. For half the participants, correct performance on female faces was rewarded, whereas for the other half correct performance on male faces was rewarded. To manipulate reward, participants were told that only the accurately decoded (male/female) faces would be counted and that results for faces of the respective opposite gender would not count towards their score. Participants were further told that if their performance was among the best they would receive an extra 2. In fact, everyone received the additional 2. Results Initial analyses revealed no significant main effects nor interactions involving participant sex. This variable was therefore dropped from further analyses. To assess whether participants were more accurate for rewarded trials than for unrewarded trials a 2 (emotion: sad vs. angry) 3 2 (reward: yes/no) repeated measures analysis of variance was conducted. Only the main effect of reward was significant, F(1,41) = 5.64, p =.22, g p 2 =.12, such that rewarded trials were decoded more accurately (M = 8.69, SD 8.21) than non rewarded trials (M = 76.32, SD 9.72; Diff = 4.37, SD 11.91, CI 95 : 8.8 to.65). A 2 (emotion: sad vs. angry) 3 2 (reward: yes/no) repeated measures analysis of variance on reaction times for correct trials revealed a main effect of reward F(1,4) = 17.16, p \.1, g p 2 =.3, such that rewarded trials were responded to faster (M = , SD ) than non rewarded trials (M = , SD 2.49; Diff = 52.32, SD 97.62, CI 95 : ).

3 Discussion As predicted, we found that rewarding participants for decoding accuracy resulted in increased decoding accuracy and thus higher levels of empathic accuracy. Participants also responded faster. In fact, even though in absolute terms and given the difficulty of the task, participants reached a surprisingly high level of accuracy overall (above 75 %), accuracy was further increased for rewarded trials. This suggests that the often made assumption that motivation can increase decoding accuracy is supported even when motivation is not derived from social context demands (for example threat) or social relationship demands as suggested by Ickes and Simpson (24) or group relations as suggested by Thibault et al. (26), but also for simple and relatively small monetary reward. That is, it is not a specific social relational stance that accounts for the higher accuracy, but the motivational effort toward gaining a reward. In addition, results suggest that the increased cognitive affective accuracy was specific to the rewarded trials and not driven by a general motivational effort. In other words, everyone was told that good performance will be rewarded thereby inducing a general motivation toward accuracy, however, rewarded trials were better recognized than non rewarded trials, suggesting a specific effort was made for these trials only. In Study 2, we wanted to assess whether this effect generalizes to affective empathy. Study 2 Study 2 had the goal to replicate Study 1 and to extend the findings to affective empathy as indexed by facial mimicry. In line with the predictions for Study 1, we predicted higher decoding accuracy for rewarded trials. We further expected more mimicry for rewarded than for unrewarded faces. Participants A total of 38 participants (4 men) with a mean age of 27.1 (SD 3.8) years participated individually. They received 8 plus the reward ( 2; see above) for their participation. Facial EMG Facial mimicry was assessed using facial EMG at the Corrugator supercilii (draws the eyebrows down and together in a frown), Orbicularis oculi (produces wrinkles around the eyes), and the Zygomaticus major (lifts the corners of the mouth in a smile) sites. Mimicry of both sadness and anger are indexed by an increase in activation of the Corrugator supercilii and a decrease of activation of the Zygomaticus major and Orbicularis Oculi. Facial activity was measured during the 24 ms following the 33 ms stimulus presentation on the left side of the face with bipolar placements of Easycap GmbH Ag/AgCl miniature surface electrodes filled with Signa gel by Parker Laboratories Inc. The skin was cleansed with lemon prep peeling and 7 % alcohol. Raw EMG data was sampled with a mindware bioamplifier with a 5 Hz notch filter at 1 Hz. The signals were band pass filtered between 3 and 3 Hz. Procedure Upon arrival at the laboratory, participants were informed about the experimental procedure and signed a consent form. Participants reclined in a comfortable chair while physiological sensors were attached. Subsequently, participants watched a 5 min relaxing video; a baseline period for the EMG measures was recorded during the last 3 min of the video. The same stimuli and procedure as in Study 1 were used. However, to allow the measurement of facial EMG, following the presentation of the emotional facial expression and the participant s response, a blank screen was shown for 18 ms to provide a long enough time period for proper EMG measurement of facial mimicry. Artifact control and data preparation The EMG data were offline rectified and smoothed. The video records for all participants were inspected for movements such as yawning and sneezing that could disrupt the EMG measures. Periods corresponding to such movements were set missing and excluded from further analyses. Within subject z-transformed difference scores (trial baseline) were calculated for each trial and binned in 24 1 ms bins. Results Initial analyses revealed no significant main effects nor interactions involving participant sex. This variable was therefore dropped from further analysis. To assess whether participants were more accurate for rewarded trials than for unrewarded trials a 2 (emotion: sad vs. angry) 3 2 (reward: yes/no) repeated measures analysis of variance was conducted. As in Study 1, only the main effect of reward was significant, F(1,37) = 9.87, p =.3, g p 2 =.21, such that rewarded trials were decoded more accurately (M = 86.77, SD 6.44) than non rewarded trials

4 Sadness (reward) Sadness (no reward) Standardized Difference Scores Time (in 1ms) Standardized Difference Scores Time (in 1ms) Anger (reward) Anger (no reward) Standadized Difference Scores Time (in 1 ms ) Standardized Difference Scores Time (in 1ms) Fig. 1 Mean standardized difference scores (over 24 ms) for facial EMG as a function of muscle site, reward and emotion condition (M = 82.89, SD 6.54; Diff = 3.87, SD 7.6, CI 95 : ). These findings replicate those of Study 1. In Study 2, no significant main effects or interactions emerged for reaction times, such that reaction times for rewarded trials (M = , SD ) were not significantly faster responded to than for unrewarded trials (M = 91.21, SD ). No other main effects or interactions emerged significantly. To assess whether the presence of a reward would influence affective empathy, we conducted a 2 (emotion: sad vs. angry) 3 2 (reward: yes/no) 3 3 (muscle site: Corrugator S., Orbicularis, O., Zygomaticus M.) analysis of variance 3 time (24 bins). 1 Mimicry of both sadness and anger is indexed by increased activation of Corrugator S. versus decreased activation of Orbicularis O. and Zygomaticus M. and planned contrasts were used to verify the presence of a mimicry pattern. A significant main effect of time, F(23, 93) = 9.47, p \.1, g p 2 =.2, as well as a reward 3 site, F(1, 93) = 4.13, p =.36, g p 2 =.1 and an emotion 3 reward 3 site, F(1, 93) = 4.4, p =.34, g p 2 =.1, which were all qualified by an emotion 3 reward 3 site 3 time interaction, F(24, 93) = 1.65, p =.28, g p 2 =.5, emerged. The means are shown in Fig. 1. Simple effects analyses revealed that both the 1 Analyses were Huyn-Feldt corrected for lack of sphericity and dfs were rounded to the next integer. planned contrast for rewarded sad trials, F(1, 37) = 5.3, p =.31, g p 2 =.12, and the unrewarded sad trials was significant across time, F(1,37) = 4.93, p =.33, g p 2 =.12. However, the pattern of means differed between rewarded and unrewarded trials. A congruent sadness mimicry pattern of increased Corrugator S. versus decreased activation of Orbicularis O. and Zygomaticus M. was found for rewarded sad trials starting at 7 ms and ending at 19 ms. By contrast, unrewarded sad trials showed a reversed pattern starting later, from 18 to 24 ms, with increased Orbicularis O. and Zygomaticus M. versus decreased Corrugator S., a pattern generally considered to be indicative of smiling. This pattern, in line with Schadenfreude, is suggestive that participants were smiling at the sad faces during non-rewarded trials, that is, taking pleasure at the misfortunes of others. In sum, whereas participants showed early evidence of affective mimicry for rewarded sad trials, unrewarded sad trials showed a late counter mimicry effect. General discussion The findings for cognitive empathy were replicated in two studies showing a specific effect whereby reward increased participants accuracy on expression discrimination. We

5 further found that reward influenced affective empathy, with participants showing greater facial mimicry on rewarded trials, but only for sadness mimicry. In this study, anger was not mimicked at all. In a recent overview, Hess and Fischer (214) note that anger is not always mimicked and suggest that anger mimicry is in many ways a contradictory activity in so far as mimicry serves a fundamentally affiliative goal and that imitating anger seems a particularly non affiliative behavior. In this sense they propose that what seems to be anger mimicry may in many cases be a reactive emotion expression in response to an unpleasant threat signal. Sadness and responding more empathically to sadness however, does serve an affiliative goal. In Study 2, sadness was mimicked and in fact, it was only mimicked during rewarded trials. This is interesting as it suggests that participants approached reward trials with a clearly more empathically-driven motivation than unrewarded trials. These results suggest that monetary reward not only influences people motivation toward accuracy and affective empathy but may also have indirect effects related to affiliative goals. By contrast, for unrewarded trials, a late component was found which suggests a counter empathic stance. This finding is evocative of findings of counter mimicry in contexts where participants are in competition with others (Lanzetta and Englis 1989) or competition is unconsciously primed (Weyers et al. 29), suggesting that participants approached the unrewarded trials with a very different motivational stance. In sum, when the empathic engagement with a face stimulus was rewarded, participants were more accurate and in the case of sadness showed more mimicry. This suggests that simple personal monetary reward quite independent of a larger social or relational motivation can enhance a person s empathic stance. This may also suggest that when researchers use emotion recognition tasks that are tiring or boring and for which participants do not see a ready motive for effort, they might underestimate people s empathic abilities. In short, human observers are not simple emotion readout machines. They spontaneously read out emotions, but their actual performance and empathic engagement depends on the situation and specifically on their motivation towards the task. In fact, it may not make sense to always give ones very best effort for emotion decoding towards all people under all circumstances. Thus, people may approach the task normally with somewhat less than their full effort and only try really hard when either the situational context (such as social threat) or an element of the task as in this study motivates them to try harder. Funding No funding was received for this research. Compliance with ethical standards Ethical standard All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional ethic committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. References de Waal, F. B. M. (28). Putting the altruism back into altruism: The evolution of empathy. Annual Review of Psychology, 59, Decety, J., & Jackson, P. L. (26). A social-neuroscience perspective on empathy. Current Directions in Psychological Science, 15, Dimberg, U. (1982). Facial reactions to facial expressions. Psychophysiology, 19(6), Hess, U., & Fischer, A. (213). Emotional mimicry as social regulation. Personality and Social Psychology Review, 17, Hess, U., & Fischer, A. (214). Emotional mimicry: Why and when we mimic emotions. Social and Personality Psychology Compass, 8, Hess, U., & Thibault, P. (29). Darwin and emotion expression. American Psychologist, 64, Ickes, W. (1997). 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