Psychophysiology, 52 (2015), 59–66. Wiley Periodicals, Inc. Printed in the USA. Copyright © 2014 Society for Psychophysiological Research DOI: 10.1111/psyp.12298

Expertise in video game playing is associated with reduced valence-concordant emotional expressivity

ANDRÉ WEINREICH, TILO STROBACH, and TORSTEN SCHUBERT Department of Psychology, Humboldt University of Berlin, Berlin, Germany

Abstract In carefully selected groups of video game playing (VGP) experts and nonexperts, we examined valence-concordant emotional expressivity. We measured electromyographic (EMG) activity over the corrugator supercilii muscle while participants viewed pleasant, neutral, and unpleasant pictures. Potential group differences concerning valenceconcordant expressivity may arise from differences concerning the participants’ emotional reactivity. To control for such differences, we concomitantly measured skin conductance response (SCR) and, in a separate affect misattribution procedure (AMP), valence transfer from the same set of stimuli. Importantly, we found attenuated valence-concordant EMG activity over the corrugator supercilii muscle in VGP experts compared to nonexperts, but no differences were evident concerning SCR or valence transfer in the AMP. The findings suggest that expertise in VGP is particularly associated with reduced valence-concordant emotional expressivity. Descriptors: Video game playing, EMG, Emotional expressivity, Valence, IAPS hedonic quality of the organism’s emotional state (core affect), unpleasant stimuli result in an emotional state with decreased hedonic quality (Russell, 2003). Importantly, changes in facial expressivity have been observed in response to the pleasantness of an encountered stimulus (Dimberg, Thunberg, & Elmehed, 2000; Larsen, Norris, & Cacioppo, 2003). Participants in a study by Cacioppo, Petty, Losch, and Kim (1986) briefly viewed pictures of scenes that were mildly to moderately pleasant or unpleasant. This study revealed that electromyographic (EMG) activity over the corrugator supercilii muscle (a muscle involved in frowning) systematically varies with stimulus valence, in that pleasant pictures elicit lower activity when compared to unpleasant pictures. These findings have repeatedly been replicated, and have also been extended to pleasant or unpleasant words and sounds (Cacioppo, Bush, & Tassinary, 1992; Dimberg, 1986; Larsen et al., 2003; Weinreich & Funcke, 2013). These findings indicate that pleasant or unpleasant stimuli spontanously activate expressive facial reactions reliably and across a broad range of stimulus modalities. In the current study, we examine the extent of this valence-concordant emotional expressivity in groups of VGP experts and nonexperts. This investigation is important because valence-concordant facial expressivity is a relevant component in many situations of social cognition and communication (Ekman, 1993; Hareli & Hess, 2010, 2012; Hess & Bourgeois, 2010). For example, there is evidence that autism, a disorder with significant deficits in social cognition and communication (Kliemann, Dziobek, Hatri, Steimke, & Heekeren, 2010), is associated with attenuated valenceconcordant facial expressivity (McIntosh, Reichmann-Decker, Winkielman, & Wilbarger, 2006; Oberman, Winkielman, & Ramachandran, 2009). Furthermore, Philipp, Storrs, and Vanman (2012) found that valence-concordant expressivity as measured by

Many people spend a lot of time playing video games, and the psychological and behavioral characteristics of these experts in video game playing (VGP) are a matter of debate in our society (Bailey, West, & Anderson, 2010; Bavelier, Green, Pouget, & Schrater, 2012; Colzato, van den Wildenberg, Zmigrod, & Hommel, 2013; Strobach & Schubert, in press). From the scientific perspective, some researchers hypothesized that playing video games may have an effect on behavioral and emotional characteristics of the individual. For example, exposure to violent video games is assumed to be associated with a decrease in prosocial behavior (Anderson et al., 2010; Bushman & Anderson, 2009; but see Ferguson, 2011), and an increase in aggressive thoughts, feelings, and actions (Anderson, Gentile, & Buckley, 2007; Anderson et al., 2010). While these findings are still under debate, the current study continues to elucidate emotional characteristics of VGP experts. In particular, we focus on characteristics concerning valence-concordant emotional expressivity. Emotions can be conceptualized as evolving from evaluative judgments of the organism concerning perceived stimuli (Scherer, 1999). In line with this proposition, emotions have been suggested to signal the valence of currently attended stimuli (Clore & Tamir, 2002; Gibson, 2008; Suri, Sheppes, & Gross, 2013; Veltkamp, Custers, & Aarts, 2011). From that perspective, stimuli are often classified according to their valence as emotionally pleasant or unpleasant. While pleasant stimuli are assumed to increase the

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The present research was supported by a grant of the German Research Foundation to TS (last author). We thank Werner Sommer, Thomas Pinkpank, and Rainer Kniesche for providing technical support. Address correspondence to: André Weinreich, Humboldt-Universität Berlin, Department of Psychology, Unter den Linden 6, 10099 Berlin, Germany. E-mail: [email protected] 59

60 electromyography over the corrugator supercilii and the zygomaticus major muscles was higher in experimental situations with high compared to low sociality. Participants in this study wore virtual reality glasses and were exposed to virtual environments that contained pleasant or unpleasant pictures. The authors additionally manipulated the sociality of the experimental situation by placing virtual humans within these virtual environments in some trials. Valence-concordant expressivity (in response to the pictures within the virtual environments) was higher in the presence compared to the absence of (virtual) humans. This finding further corroborates the social significance of valence-concordant facial expressivity. In addition, valence-concordant emotional expressivity has been suggested to reflect embodied signals that facilitate comprehension of the evaluative meaning inherent to encountered stimuli. For example, it has been found that blocking the free activity of facial muscles reduces comprehension of sentences with certain emotional content (Havas, Glenberg, Gutowski, Lucarelli, & Davidson, 2010) or of the meaning of others’ facial expressions (Oberman, Winkielman, & Ramachandran, 2007), and decreases the effects of perceived emotional stimuli on subsequent evaluative judgments (Foroni & Semin, 2011). In line with the “embodied signal idea” stronger valence-concordant expressivity has been found if the participants’ task requires the comprehension of the stimuli’s value than when compared to tasks where the evaluative meaning of the stimuli was not relevant (Niedenthal, Winkielman, Mondillon, & Vermeulen, 2009; Weinreich & Funcke, 2013). Together, these findings indicate that valence-concordant emotional expressivity is a relevant component of psychological functioning. In addition, these findings indicate that the extent of valence-concordant expressivity can differ between individuals (cf. Bourgeois & Hess, 2008; McIntosh et al., 2006; Oberman et al., 2009). Finally, findings from Cacioppo et al. (1992) also suggest that valence-concordant expressive reactions can be modified by topdown control processes. The authors exposed participants to pictures of pleasant, neutral, or unpleasant scenes, and additionally provided instructions that differed between individuals: no instruction, inhibit-expression instructions, and amplify-expression instructions. Results revealed that valence-concordant expressivity was highest in the amplify and lowest in the inhibit condition, illustrating the impact of control processes for this expressivity. Interestingly, recent evidence (Colzato, van Leeuwen, van den Wildenberg, & Hommel, 2010; Karle, Watter, & Shedden, 2010; Schubert & Strobach, 2012; Strobach, Frensch, & Schubert, 2012) points to superior executive control abilities in VGP experts compared to nonexperts. This improved controllability of (behavioral) executions may also hold for valence-concordant expressivity. Considering the relevance of VGP in our society (e.g., one third of the German as well as half of the U.S. adult population consume video games several times per month or more, Strobach & Schubert, in press), it is thus quite surprising that no study has yet examined characteristics concerning valence-concordant expressivity in VGP experts. In the current study, we used a picture-viewing procedure and exposed VGP experts and nonexperts to unpleasant, neutral, and pleasant pictures from the International Affective Picture System (IAPS; Lang, Bradley, & Cuthbert, 2008). The IAPS catalogue provides a collection of emotional pictures with diverse environmental and “ecologically valid” content. Importantly, there is a database reflecting the stimuli’s valence in a normative fashion. In order to examine the participants’ valence-concordant emotional

A. Weinreich, T. Strobach, and T. Schubert expressivity on perceiving these IAPS pictures during the pictureviewing procedure, we measured facial EMG over the corrugator supercilii muscle region (Fridlund & Cacioppo, 1986). As illustrated above, EMG over the corrugator supercilii muscle has repeatedly been proved to reliably reflect valence-concordant emotional expressivity in response to stimuli of diverse modalities (Cacioppo et al., 1992; Dimberg, 1986; Larsen et al., 2003). The isolated observation of corrugator supercilii muscle activity, however, is not sufficient to conclude about possible VGPrelated characteristics concerning valence-concordant expressivity. This is so because potential differences in valence-concordant emotional expressivity could be additionally related to, or mediated by, differences in the emotional reactivity of the participants. For instance, individuals may show attenuated valence-concordant emotional expressivity not because of a genuinely attenuated expressivity but because unpleasant and/or pleasant pictures are perceived to be rather less emotional (i.e., neutral). In order to control for such differences in emotional reactivity, we additionally measured the skin conductance response (SCR) within the identical trials of the picture- viewing procedure. Usually, both unpleasant and pleasant stimuli involuntarily provoke stronger SCR when compared to neutral stimuli (Bradley, Codispoti, Cuthbert, & Lang, 2001). Possible differences in emotional reactivity between VGP experts and nonexperts would be indicated by differences concerning the extent of this pattern. Thus, the accompanying measurement of SCR allows us to control for differences in emotional reactivity that may explain potential differences within valence-concordant emotional expressivity. Similarly, to comprehensively control for emotional reactivity, we measured valence transfer from the same pictures in an affect misattribution procedure (AMP; Payne, Cheng, Govorun, & Stewart, 2005) in a separate task. Participants in the AMP are required to evaluate emotionally ambiguous Asian ideographs. Each of these ideographs is preceded by a prime stimulus. A number of studies have shown that the prime’s valence transfers to the following ideograph and affects the evaluation of the latter (Payne, Govorun, & Arbuckle, 2008; Payne, Hall, & Cameron, 2010). As a result, ideographs following pleasant primes are evaluated to be more pleasant than ideographs following unpleasant primes. The difference of the evaluations between the pleasant and unpleasant condition reflects the extent of valence transfer. In order to measure emotional reactivity to the stimuli from the pictureviewing procedure, we presented the same set of pictures as primes in the separate AMP. Importantly, the task demands of the AMP and the picture-viewing procedure are similar, in that both do not require participants to evaluate these pictures explicitly (see also Payne, Burkley, & Stokes, 2008). Thus, we obtained a measure of how participants react to the “normative” pleasantness of the pictures in a situation that is comparable to the picture-viewing procedure. This is important as differences in how participants react to the pleasantness of the pictures might confound any potential group differences concerning valence-concordant expressivity in the picture-viewing procedure. To sum up, by measuring EMG over the corrugator supercilii muscle in a picture-viewing procedure with standardized stimulus material (i.e., stimuli of the IAPS), we examined VGP expertiserelated characteristics concerning valence-concordant emotional expressivity. According to Cacioppo et al. (1992), activity over the corrugator supercilii muscle should decrease with the pleasantness of the picture content in the picture-viewing procedure. Importantly, we examined whether the extent of this valence-concordant expressivity differs between VGP experts and nonexperts. By

VGP and valence-concordant emotional expressivity

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concomitantly assessing SCRs in the same task situations, and assessing valence transfer from the same set of stimuli in an AMP task, we controlled for potential confounds concerning emotional reactivity.

Table 2. Normative Values on Valence and Arousal of the IAPS Pictures and Their Assignment to the Respective Valence Class and Set Set A

Method Participants Forty-two male participants ranging from 19 to 30 years of age (M = 24.3, SD = 3.01) took part in the experiment; only males underwent testing because of the relative scarcity of females with sufficient experience in video game playing. Participants were recruited using the Institute’s online server. To counterbalance a general level in motivation between the VGP experts group and the VGP nonexperts group to participate in the study (Boot, Blakely, & Simons, 2011), two similar but separate announcements for VGPexperienced students and VGP-inexperienced students were created for the recruitment (Schubert & Strobach, 2012). We assume that this way of recruiting different participant groups has no or negligible expectation effects on our experimental measurements. Group differences would require several conditions to be met to result in effects on our experimental measurements. First, both groups would need to be aware of our hypotheses under consideration (which we did not make explicit). Second, beyond simple awareness of hypotheses, participants would also need an explicit understanding of how hypotheses should be borne out in data (Green, Strobach, & Schubert, 2013). As a consequence, we assume that an appropriate recruiting strategy was selected. Furthermore, the implicit nature of the measures that we used reduces the impact of group-related differences concerning the participants’ expectations on the measurement outcome (De Houwer, 2006). While 24 recruited participants had experience in playing video games of 10 or more hours a week (VGP experts), 18 had 1 or zero hours a week of experience in playing video games within the past 12 months (VGP nonexperts). All participants had normal or corrected-to-normal vision, no experience with the semantic content of Asian ideographs (see the AMP), were right-handed according to the Edinburgh Handedness Inventory (Oldfield, 1971), and were German native speakers. All signed informed consent before the experiment and were either monetarily compensated or received course credit. To better characterize the participants, they were asked to indicate the number of years of formal education they had

Table 1. Characteristics of Video Game Playing (VGP) Experts and Nonexperts by Means (Standard Deviations)

Age (years) Handednessa Education (years) Health statusb IQ (APM)c Attention performance (D2)c a

VGP experts

Nonexperts

23.8 (3.2) 92.3 (21.8) 16.5 (1.8) 4.2 (.6) 11.0 (2.2) 199.0 (36.1)

24.8 (3.1) 97.5 (7.3) 18.2 (3.3) 4.3 (.7) 10.6 (2.7) 180.8 (42.0)

Handedness measured using the Edinburgh Handedness Inventory Lateralization Quotient, fully right-handed = 100. b Health status (1 = poor, 5 = excellent). c Paper-and-pencil questionnaires measured IQ via Advanced Progressive Matrices (APM, N of correct items out of 18 items) as well as attention performance score via the D2 test.

Set B

Category

IAPS

Valence

Arousal

IAPS

Valence

Arousal

Unpleasant

2276 9320 9250 3400 6230

2.67 2.65 2.57 2.35 2.37 2.52 4.94 4.55 4.82 5.52 5.71 5.11 7.24 7.24 7.03 7.12 7.33 7.19

4.63 4.93 6.60 6.91 7.35 6.08 1.76 2.27 2.39 2.42 2.79 2.33 4.12 4.30 6.34 6.59 7.35 5.74

9280 2205 3030 6260 6510

2.80 1.95 1.91 2.44 2.46 2.31 5.04 4.94 4.83 5.00 4.82 4.93 7.49 7.45 6.99 7.01 7.57 7.30

4.26 4.53 6.76 6.93 6.96 5.89 2.00 2.28 2.41 2.42 2.43 2.31 4.19 4.79 6.74 6.84 6.99 5.91

Mean Neutral

Mean Pleasant

Mean

7010 7110 7491 7490 2580 1500 2331 4607 8180 8030

7004 7950 2190 7000 7217 2395 1463 4670 8186 5621

Note. IAPS = International Affective Picture System.

received and to rate their current general health status relative to their age group on a scale of 1 (poor) to 5 (excellent). Further, we conducted a paper-and-pencil intelligence test (Advanced Progressive Matrices; Raven, Raven, & Court, 2004) and measured attention performance (D2 test; Oswald, Hagen, & Brickenkamp, 1997). Overall, we found no significant difference between both VGP experts and nonexperts in these measures (see Table 1 for further details). Materials Two sets with fifteen different pictures from the IAPS (Lang et al., 2008) were used as emotional stimuli (Table 2). Half of the participants in each group (VGP experts vs. nonexperts) were exposed to Set A, the other half to Set B. The pictures in each set could be classified into three categories with five pictures each: pleasant, neutral, and unpleasant. With respect to the normative database of the IAPS in both sets, pictures with pleasant content were rated to be more pleasant than pictures with neutral content, and pictures with neutral content were rated to be more pleasant than pictures with unpleasant content (all ts > 9.28, ps < .00002). In addition, the pictures with unpleasant and pleasant content were more arousing than the pictures with neutral content (all ts > 5.11, ps < .001), while arousal did not differ between pictures with unpleasant and pleasant content in either of the two picture sets (all ts < 0.41, ps > .7). Finally, there were no differences between the two picture sets in either of the categories (all ts < 0.82, ps > .44). For the AMP, we additionally selected 75 Asian ideographs, which have been pretested for their emotional ambiguity. Apparatus EMG was recorded using Ag/AgCl miniature surface electrodes. In accordance with the standard electrode placements recommended by Fridlund and Cacioppo (1986), two electrodes were placed over the left eyebrow (corrugator supercilii). A reference electrode was placed on the upper right forehead over a region that contains

62 relatively few muscles. Electrodes were filled with high conducting water-soluble electrolyte gel. Electrode sites were cleaned and rubbed with prep pads dampened with alcohol to decrease skin resistance. The raw electromyography signal was amplified by a factor of 50,000 at a band-pass of 8 Hz–10 kHz (Coulbourn V75-04), rectified and integrated (Coulbourn V76-23; time constant 0.1 s). Skin conductance electrodes were placed adjacently on the hypothenar eminence of the left palmar surface, using standard electrodes filled with water-soluble electrolyte gel. The signal was acquired with a Coulbourn S71-22 skin conductance coupler. The output voltage of both the EMG and SCR signal was digitized at 16-bit and 1000 Hz (USB 1608 FS by Measurement Computing). Procedure All stimuli were centrally presented against a gray background (RGB (red/green/blue): 162, 162, 162) on a 24-inch LED screen using a 60 Hz refresh rate and a resolution of 1,680 × 1,050 pixels. The color IAPS pictures were expressed in a resolution of 1,024 × 768 pixels. Asian ideographs in the AMP were displayed in black in a resolution of 300 × 300 pixels. Stimulus presentation and timing were controlled using MATLAB (The Mathworks Inc.) and Psychophysics Toolbox version 3 (Brainard, 1997; Pelli, 1997) running on a standard computer. Picture-viewing procedure. In each trial, the respective picture was shown for 3 s. Each picture was preceded and followed by a 3-s presentation of its own scrambled version. Each of the 15 pictures was presented twice. Stimulus sequence was random for each participant but restricted so that each picture was presented once in the first half and once in the second half of trials and so that a particular stimulus could only recur after at least 4 trials. We instructed participants to pay close attention to the presented pictures over the whole presentation time, as the computer would ask a (not yet defined) question concerning these pictures at the end of the viewing procedure. At the end of the picture viewing part, we presented one new (i.e., not presented before) picture and asked participants to decide whether it had occurred or not during the experiment. Affective misattribution procedure. In the AMP, participants were informed that they were to evaluate the pleasantness of an Asian ideograph that was visible only for a short time. As targets, we used 75 Asian ideographs. The 15 IAPS pictures served as primes. Participants were instructed to respond only to the targets, while the respective prime was explained as a warning signal, informing that the relevant stimulus follows shortly afterwards. Each trial started with a black fixation point for 1 s. After that, the prime was presented for 83 ms, followed by a blank gray screen for 117 ms and the target for 100 ms. Following the target, a mask consisting of a scrambled version of the respective ideograph appeared until the participant responded with either the left (“rather unpleasant”) or right (“rather pleasant”) arrow key. Altogether, 75 trials were completed so that each prime was used five times, while targets differed for each trial. The sequence and pairing of primes and targets were randomized with the restriction that each prime could only recur after at least four trials. General design. The general design was as follows: Each participant performed the picture-viewing task first. This task was followed by the AMP. At the end of the experiment, participants were

A. Weinreich, T. Strobach, and T. Schubert informed about the actual purpose of the study. Including electrode placement and preparation, the whole experiment took approximately 30 min to complete. Results Picture-Viewing Procedure First, we examined the amplitude of the EMG signal averaged over the entire 3,000-ms interval of stimulus presentation, from which we subtracted the respective mean amplitude during a 500-ms prestimulus baseline interval. A 3 × 2 factorial mixed measures analysis of variance (ANOVA; all effects Huynh-Feldt corrected) with the repeated factor valence (unpleasant, neutral, pleasant) and the between-participants factor group (VGP experts vs. nonexperts), and the mean EMG activity as the dependent variable revealed a significant main effect of valence, F(2,80) = 6.58, p = .004, η2 = .14. As expected, mean amplitude over the corrugator supercilii muscle decreased as stimulus valence became more pleasant. Across all participants, EMG activity was greater in response to unpleasant compared to neutral, t(41) = 2.26, p = .029, and pleasant stimuli, t(41) = 2.56, p p = .014. The difference between neutral and pleasant stimuli failed to reach significance (t = 0.92). However, most importantly, valence-concordant activity of the corrugator supercilii muscle varied differently in both groups of participants as is revealed by the significant interaction of group and valence, F(2,80) = 3.51, p = .042, η2 = .08. The following comparisons illuminate the crucial interaction of group and valence on EMG activation during the picture presentation. In VGP nonexperts, EMG activation was more pronounced in response to unpleasant than when compared to both pleasant, t(17) = 2.34, p = .032, and neutral pictures, t(17) = 2.11, p = .05. The particular difference between neutral and pleasant stimuli was not significant, t(17) = 1.05, p = .31. Importantly, in the group of VGP experts, none of the comparisons reached significance (largest, t(23) < 1.34). No main effect of group was observed (F < 0.1, p > .86). Mean amplitudes are illustrated in Figure 1. Next, we analyzed the SCR data within the same trials of the picture-viewing procedure by continuously decomposing the SCR data using LEDALAB (Benedek & Kaernbach, 2010) and thus isolating the actual physical driver of sympathetic activity. We examined the amplitude of the decomposed SCR signal averaged over a 3,000-ms interval starting 1,000 ms after stimulus onset (Figure 2). A 3 × 2 factorial mixed measures ANOVA with the repeated factor valence (unpleasant, neutral, pleasant) and the between-participants factor group (VGP experts vs. nonexperts) revealed a significant main effect of valence only, F(2,80) = 10.80, p < .001, η2 = .21. Pairwise t tests revealed a significant difference between unpleasant and neutral stimuli, t(41) = 3.87, p = .0004, and between pleasant and neutral stimuli, t(41) = 4.85, p = .00002. The main effect of and the interaction with group were nonsignificant (both Fs < 1.33, ps > .25). Affect Misattribution Procedure In order to examine potential group differences in how participants react to the “normative” valence of the pictures, we calculated the frequency of rather pleasant responses in the AMP for each of the three stimulus types. We entered these values in a mixed measures ANOVA with valence (unpleasant, neutral, pleasant) as a repeated factor and group (VGP experts vs. nonexperts) as a betweenparticipants factor. This ANOVA showed a significant effect of

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Figure 1. Mean electromyographic (EMG) amplitude (μV) over corrugator region relative to the 500-ms prestimulus baseline interval plotted against stimulus valence for the groups of video game playing (VGP) experts and nonexperts. Error bars represent ± 1 SE.

Figure 3. Mean proportion of pleasant responses to the ideographs in the AMP plotted against prime valence for the groups of video game playing (VGP) experts and nonexperts. Error bars represent ± 1 SE.

prime valence, F(2,80) = 7.45, p = .003, η2 = .16, on ideograph evaluation. Across all participants, the ideograph was more frequently judged as rather pleasant when a pleasant prime was shown before, whereas frequency of this response was lowest when the ideograph followed a prime with unpleasant content. Mean frequencies of ratings are plotted against prime valence in Figure 3. Pairwise t tests revealed a significant difference between unpleasant and pleasant primes, t(41) = 2.88, p = .006, and between unpleasant and neutral primes, t(41) = 3.73, p = .001, but no difference between pleasant and neutral stimuli (t = 0.00, p = 1). The main effect of and interaction with group were nonsignificant (both Fs < 1.38, ps > .05).

Finally, we examined whether the crucial interaction that we observed in the primary ANOVA on the EMG data can still be found if estimates of emotional reactivity were included as covariates. For SCR and the AMP, we subtracted the values for the neutral condition (baseline) from the values for the pleasant and unpleasant condition, respectively. Then, we included these four values as covariates in the primary ANOVA on the EMG data. This 3 × 2 factorial mixed measures ANCOVA (all effects Huynh-Feldt corrected) with the repeated factor valence (unpleasant, neutral, pleasant) and the between-participants factor group (VGP experts vs. nonexperts) and the four estimates of emotional reactivity as covariates, and the mean EMG activity as the dependent variable revealed a significant main effect of valence, F(2,72) = 4.14, p = .021, η2 = .1, and, importantly, a significant interaction of group and valence, F(2,72) = 4.85, p = .011, η2 = .12. Discussion

Figure 2. Mean decomposed skin conductance response (SCR) plotted against stimulus valence for the groups of video game playing (VGP) experts and nonexperts. Error bars represent ± 1 SE.

We investigated valence-concordant emotional expressivity in groups of experts and nonexperts in VGP. In particular, we measured activity over the corrugator supercilii muscle (EMG) while participants were exposed to pleasant, neutral, and unpleasant pictures from the IAPS (Lang et al., 2008) within a picture-viewing procedure. As expected, the results indicate increasing activity of the corrugator supercilii muscle with decreasing pleasantness of the stimuli (cf. Larsen et al., 2003). Importantly, this effect was significantly reduced in VGP experts when compared with nonexperts. This suggests that VGP expertise is associated with reduced valence-concordant emotional expressivity. Importantly, the observation of attenuated valence-concordant expressivity seems not to be caused by potential group differences concerning emotional reactivity. To control for group differences in emotional reactivity, we concomitantly assessed SCRs within the same trials of the picture-viewing procedure, and additionally assessed valence transfer from the same stimuli in a separate AMP. In both parameters (SCR and valence transfer), we could not find evidence for group differences concerning emotional reactivity. In

64 particular, all participants showed a comparable pattern of stronger SCR in response to both pleasant and unpleasant compared to neutral pictures. Furthermore, within the AMP the probability of pleasant responses towards the ideograph increased with the pleasantness of the preceding picture to a comparable extent in VGP experts and nonexperts. Participants from both groups comparably reacted to the emotional content of the pictures according to the normative classification. Finally, the group differences concerning valence-concordant expressivity remain significant if we control for emotional reactivity as covariates. As a whole, these findings suggest that the group differences concerning valenceconcordant expressivity cannot be attributed to differences in emotional reactivity. In the following, we discuss how these observations can be reconciled with recent findings and theoretical assumptions about VGP expertise, and the genesis of valence-concordant facial expression, respectively. Semantic network models of emotion (Berkowitz, 1990; Bower, 1981; Lang, 1979) consider emotions to be represented in a propositional associative network where stimuli and the related responses are parts in directly interconnected information units. According to these models, valence-concordant facial expressivity should always occur as long as the encountering stimulus has been sufficiently encoded. Our findings of attenuated valence-concordant expressivity may therefore be due to an insufficient encoding of the stimuli’s emotional content in VGP experts compared to nonexperts. The current SCR data and data of the AMP, however, rule out this explanation. In particular, insufficient encoding of the stimuli’s emotional content should also be reflected by reduced emotional reactivity (SCRs and valence transfer). This is not the case. Both groups of participants show comparable emotional reactivity. Within the associative account, however, the findings may suggest a weaker link between the sufficiently encoded representations of valence (feature) and the concordant activity of the corrugator supercilii muscle (response) in VPG experts compared to nonexperts. Several researchers (e.g., Hareli & Hess, 2012; Hess & Bourgeois, 2010) assign valence-concordant facial expressivity a socioemotional communicative function that informs surrounding persons about the emotional quality of a current situation (“Be careful, this may be dangerous” vs. “Look, this is awesome”). Thus, a lower frequency of socioemotional communication in VGP experts compared to nonexperts may explain the hypothetically loose link between the sufficiently encoded representation of valence and the associated activity of the corrugator supercilii muscle in VGP experts compared to nonexperts. Alternatively, it is possible that VGP experts intentionally or habitually inhibit valence-concordant expressivity. There is evidence that valence-concordant expressivity can be actively modulated or modified by top-down processes. In particular, Cacioppo, Bush, and Tassinary (1992) exposed participants to slides of pleasant, neutral, or unpleasant scenes under no instruction, inhibit-expression instructions, and amplify-expression instructions (see also introduction). Results revealed that facial EMG activity was highest in the amplify and lowest in the inhibit condition. Furthermore, recent evidence (e.g., Strobach et al., 2012) points to increased executive control abilities in VGP experts when compared to nonexperts. This augmented controllability of executions may also hold for the execution of valence-concordant expressivity. Inhibiting expressivity may be beneficial, because valence-concordant facial muscular activity has been suggested to reflect embodied signals (Niedenthal et al., 2009) that potentially facilitate the comprehension of the evaluative meaning inherent to encountered stimuli. In some situations and tasks,

A. Weinreich, T. Strobach, and T. Schubert however, these embodied signals may unnecessarily distract and interfere with a focal task (e.g., gaming, carefully attending to presented pictures). Augmented control of valence-concordant expressivity may be beneficial to reduce such distracting embodied input and to facilitate performance in a currently focused task. This proposition may also explain that speed of information processing in certain tasks seems to be superior in VGP experts when compared to nonexperts (Dye, Green, & Bavelier, 2009). However, because of the quasiexperimental design of the current study, we cannot infer causal associations between VGP and the observed characteristics. In particular, it is not clear whether attenuated valence-concordant expressivity is inherent to the VGP participants per se, or whether this characteristic has evolved due to intensive VGP. Note that similar debates about a potential causal relation between VGP and certain psychological and behavioral characteristics have been raised in the past (Green & Bavelier, 2003; Schubert & Strobach, 2012; Strobach et al., 2012; but see Boot et al., 2011). Future studies should, therefore, apply an intervention-based approach in order to assess a possible causality of VGP for the degree of participants’ valence-concordant expressivity. In particular, one may address the question whether the extent of valence-concordant expressivity is related to “expertise” concerning social-emotional communication. For example, one may ask participants in an experimental group to facially express the evaluative meaning inherent to pictures of happy and angry faces, while a control group of participants may be asked to judge the gender of these stimuli instead. By doing so, one may strengthen the (hypothetical) link between valence and activity over the corrugator supercilii muscle in the experimental group. Following this intervention phase, one may measure valence-concordant expressivity of the participants of both groups within the picture-viewing procedure that has also been conducted in the current study. By doing so, one may compare the extent of valence-concordant expressivity in the same situation and to the same stimuli depending on the extent of prior socioemotional communication. Considering the associative-link hypothesis outlined above, one would expect stronger valence-concordant expressivity in the participants that practiced socioemotional communication facially in advance. Alternatively, future studies may examine whether controllability of executions is associated with valence-concordant expressivity in situations where embodied signals do not necessarily facilitate the performance in a given task (e.g., in a mere picture-viewing procedure). Recently, Fischer and Hommel (2012) induced different states of executive control by asking their participants to engage in convergent (vs. divergent) thinking. One may replicate this induction procedure and then examine valence-concordant expressivity in the same picture-viewing procedure that has been conducted in the current study. If the ability to assert control over executive functions was associated with the controllability of (distracting) embodied signals, one would expect reduced valence-concordant expressivity in participants with high (convergent thinking) compared to low (divergent thinking) states of executive controllability. In the current study, we did not find any group differences in emotional reactivity (SCR, valence transfer in the AMP). These findings rule out that the observed group differences in valenceconcordant expressivity are due to differences in emotional reactivity. Furthermore, they also contribute to the discussion of potential effects of VGP on emotional reactivity. Existing studies that examined emotional reactivity of VGP experts and nonexperts delivered mixed findings. While some studies (Bailey, West, & Anderson, 2011; Bartholow, Bushman, & Sestir, 2006) found that VGP expertise is not associated with characteristics concerning

VGP and valence-concordant emotional expressivity

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emotional reactivity to either unpleasant, neutral, or pleasant stimuli, a recent study by Bailey and West (2013) suggests a generally increased reactivity to both unpleasant and pleasant stimuli in VGP experts when compared to nonexperts. These studies focused on event-related potentials within electroencephalography. In the current study, we assessed emotional reactivity by means of SCR and by means of valence transfer in the AMP, which was performed one of the first times to the best of our knowledge. As we did not observe any group differences in either of the measures, our results corroborate the proposition that VGP expertise is not associated with characteristics within emotional reactivity. Summary In a picture-viewing procedure, we examined valence-concordant facial expressivity to unpleasant, neutral, and pleasant pictures in a

sample of VGP experts and nonexperts. By means of EMG over the corrugator supercilii muscle region, we found attenuated valenceconcordant expressivity in VGP experts when compared to nonexperts. To examine whether this characteristic can be explained by group differences concerning emotional reactivity, we additionally assessed SCR within the same picture-viewing procedure, and also measured valence transfer in a separate AMP with the same stimuli. As indicated by comparable SCR, and additionally by comparable valence transfer in the AMP in both groups, attenuated valence-concordant expressivity in VGP experts compared to nonexperts cannot be attributed to differences in emotional reactivity. Even though the implications of our study are limited due to its quasiexperimental nature, we argue that we offered important insights into VGP-associated emotional characteristics and significantly contributed to the debate on risks and chances inherent to VGP.

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