c. The Present Experiment

In order to provide a conclusive test of the different effects of anger versus sadness primes on effort mobilization, we investigated the interaction between masked anger versus sadness stimuli and objective task difficulty on effort-related cardiovascular response. As outlined above and shown by Silvestrini and Gendolla (2011c), objective task difficulty and affect primes should have an additive effect on the level of subjective demand and thus effort intensity, leading to a moderation of objective task difficulty’s impact.

78 Figure 6. Theoretical predictions for the combined effect of anger versus sadness primes and objective task difficulty on effort-related cardiovascular response. The averaged emotional expressions show examples of the AKDEF database (Lundqvist & Litton, 1998) used as affect primes in the present experiment. Figure adapted from Gendolla (2000).

As depicted in Figure 6, during an easy task we predict lower effort-related cardiovascular response for participants exposed to anger primes than participants exposed to sadness primes. This is because sadness is associated with difficulties and should thus increase subjective task difficulty. By contrast, anger primes should lead to higher effort than sadness primes in a difficult task. This is because anger primes should set subjective demand on a high but still possible level, while sadness primes lead to the experience of too high demand, resulting in disengagement. Thus, in summary, we predict a crossover interaction effect between the affect primes and objective task difficulty on effort-related cardiovascular response, especially PEP. Moreover, according to previous research, we anticipated corresponding effects on SBP, although PEP is the more reliable and valid measure of ß-adrenergic impact and effort, as outlined above.

79 II.3.3. Method

II.3.3.a. Participants and Design

Seventy-nine healthy undergraduate students from various disciplines of the University of Geneva (52 women, 27 men, mean age 21 years) were randomly assigned to the conditions of a 2 (prime: anger vs. sadness) X 2 (task difficulty: low vs. high) between persons design⁶. Four participants were excluded from the statistical analyses because of incomplete data, leaving a final sample of N = 75. Participants received 10 Swiss francs (approximately 12 USD) or course credit for their participation in the experiment.

II.3.3.b. Affect Primes

Low contrast, low resolution, gray scale, front perspective pictures of averaged human facial expressions from The Averaged Karolinska Directed Emotional Faces (AKDEF; Lundqvist & Litton, 1998) inventory were used as affect primes. Half of the faces were female (AKDEF pictures FNES, FSAS, FANS) and half were male (AKDEF pictures MNES, MSAS, MANS).

II.3.3.c. Apparatus and Physiological Measures

A Cardioscreen 1000 system (Medis, Ilmenau, Germany) assessed electrocardiogram (ECG) and thoracic impedance (impedance cardiogram, ICG) signals (see Scherhag, Kaden, Kentschke, Sueselbeck, & Borggrefe, 2005 for a validation of the system). Four pairs of disposable spot electrodes (2 X 16-mm Ag/AgCl, Red Dot, 3M) were placed on the right and left sides of participants’ neck and on the right and left sides of the axillary line at the height of the xiphoid. The signals with a sampling rate of 1000 Hz. ICG and ECG measures were analyzed with BlueBox 2.v1.21 software (Richter, 2010a). The first derivative of the change in thoracic impedance was calculated, and the resulting dZ/dt signal was ensemble averaged over periods of 1 min using the detected peaks (Kelsey & Guethlein, 1990). To obtain PEPvalues (the time interval between R-onset and B-point, as defined by Berntson et al., 2004), B-point location was estimated

6. The distribution of women and men was balanced between the experimental conditions.

80 based on the RZ interval as proposed by Lozano et al. (2007) and manually corrected as recommended by Sherwood et al. (1990). Additionally, we assessed SBP and DBP (in millimeters of mercury [mm Hg]) with a Dinamap ProCare 300 monitor, (GE Medical Systems Information Technologies Inc., Milwaukee, WI) using oscillometry. A blood pressure cuff (DuraCuf) was placed above the brachial artery of participants’left arm. The cuff automatically inflated in 1-min intervals during habituation and task performance periods.

II.3.3.d. Procedure

The procedure had been approved by the local ethical committee. The experiment was run in individual sessions. After having obtained informed consent, participants were seated in a comfortable chair in front of a computer. The experimenter attached the blood pressure cuff and the electrodes and went to an adjacent control room. After answering some biographical questions, participants indicated their momentary affective state before exposure to the affect primes by rating the two highest loading items of the positive (happy, joyful) and negative (sad, depressed) affect scales of the UWIST mood checklist (Matthews, Jones, & Chamberlain, 1990). Two adjectives assessing anger (angry, irritated) were added. Ratings were made on 7-point scales (1—not at all, 7—very much).

Next, we recorded cardiovascular baseline values during a habituation period (8 min) in which participants watched a hedonically neutral documentary film about Lithuania. After this, participants received instructions (“Please respond as quickly and accurately as possible”) for a short-term memory task adapted from Sternberg (1966).

Task trials started with a fixation cross (1000 ms) followed by a picture of a facial expression of the AKDEF database (26 ms). In each condition, one-third of the faces showed an emotional expression (anger vs. sadness) while the other two-thirds were emotionally neutral faces—which has been found to be the most effective in the present priming paradigm (Silvestrini & Gendolla, 2011b)⁷. The facial expression pictures were immediately backward masked with a random dot pattern (125 ms), which was followed by a string of 4 letters in the easy condition versus 7 letters in the difficult condition (750 ms) and a backward mask consisting of a row of the letter “X”. A target letter appeared in

7 In order to assure that participants were presented with emotional expressions from task onset on, we randomized in portions of 6 trials.

81 the center of the screen, and participants indicated by pressing a “yes” or a “no” key if that letter had been included in the previously presented string. The letter remained on the screen until participants gave a response (maximal response window: 2 s). Then, the message “response entered” appeared. In case of no response, the message “Please answer more quickly” was presented. To keep performance time and number of presented primes constant, this message appeared for 4 s minus participants’ reaction time. The inter-trial intervals randomly varied between 2 s and 5 s. The task was comprised of 32 trials and started after a training session of 10 trials, including correctness feedback and only neutral facial expressions as primes. No correctness feedback was given during the task to avoid affective reactions (e.g., Kreibig, Gendolla, & Scherer, 2010) that could interfere with the affect primes’ impact.

After the task, participants retrospectively rated subjective task difficulty, ability to succeed, quantity of mobilized effort, and the importance of success on 7-point scales (1—not at all, 7—very much). Then, the same affect items that had been assessed at the beginning of the experiment were rated again to control for possible affect primes effects on participants’ conscious feelings. Subsequently, we applied a funnel debriefing procedure to assess if participants were able to determine the aim of the study and to describe the stimuli presented during the task.

Finally, we ran a prime recognition test. In 4 trials, a face from the AKDEF database (2 neutral, 2 emotional) was presented for 26 ms and backwardly masked for 125 ms (as during the task). Then, two faces appeared on the screen, and participants had to decide which one had been flashed in just beforehand by pressing respective computer keys. Finally, participants were debriefed, thanked, and received course credit or payment for their participation.

82 II.3.4. Results

II.3.4.a. Cardiovascular Baselines

Baseline values for PEP, SBP, DPB, and HR (see Table 1) were calculated by averaging values of the last 5 min of the habituation period (Cronbach’s as > .97)⁸. Two (prime) X 2 (difficulty) between-persons analyses of variance (ANOVAs) found no significant a priori differences between the conditions for any cardiovascular index (ps >

.27).

Note. PEP = pre-ejection period (in ms); SBP = systolic blood pressure (in mmHg); DBP

= diastolic blood pressure (in mmHg); HR = heart rate (in beats/min).

8 We calculated the cardiovascular baseline values from the 5 last min of the habituation period, because there was a decline in assessed values over the first 3 min. For the last 5 min of the habituation period, the values were stable and did not differ significantly from one another (ps .78).

83 Preliminary statistical analyses found also no gender differences in cardiovascular baseline values for PEP and HR (ps > .66). However, men had higher SBP (M = 110.92, SE = 2.43 vs. M = 99.17, SE = 1.43) and DBP baseline values (M = 58.88, SE = 1.74 vs.

M = 55.39, SE = 0.72) than women (ps < .03), which is usual (Wolf et al., 1997).

II.3.4.b. Cardiovascular Reactivity

Task-related cardiovascular values were determined by averaging the 1-min change scores for PEP, SBP, DBP, and HR during task performance, which showed high internal stability (Cronbach’s as > .98). Reactivity scores were determined by subtracting baseline values from values assessed during task performance. Preliminary analyses found a significant association between PEP baseline values and reactivity scores, F(1,70)

= 5.41, p < .02, η² = .07. Therefore, we analyzed the PEP reactivity scores with an analysis of covariance (ANCOVA) controlling for this association in order to prevent initial value or carryover effects. No other reactivity scores were associated with their respective baseline values (ps > .45). Furthermore, there were no significant gender differences in reactivity scores (ps > .07), and considering gender as covariate in the analyses of cardiovascular reactivity did not moderate any of the effects reported below.

Pre-ejection Period (PEP) Reactivity.

A 2 (prime) X 2 (task difficulty) ANCOVA of PEP reactivity with PEP baseline values as covariate revealed the expected significant prime X difficulty interaction, F(1,70) = 7.89, p < .006, η² = .10, in absence of significant main effects (ps > .16). Cell means are depicted in Figure 7. Focused comparisons revealed for the easy condition the expected stronger PEP reactivity in the sadness-prime condition (M = -2.45, SE = 0.73) than in the anger-prime condition (M = -0.35, SE = 0.73), t(70) = 1.93, p < .03, η² = .05⁹. As anticipated, this effect was inversed in the difficult condition. Here, PEP reactivity in the anger-prime condition (M = -3.39, SE = 0.68) was significantly stronger than in the

84 Figure 7. Means and standard errors of cardiac pre-ejection period reactivity (in ms) during task performance.

HR, SBP, and DBP reactivity

A 2 X 2 ANOVA of HR reactivity also found a significant prime X difficulty interaction, F(1,71) = 7.54, p < .008, η² = .10, in absence of significant main effects (ps >

.16). As depicted in Figure 8, the reactivity pattern of HR corresponded to that of PEP.

HR reactivity in the sadness prime/ easy condition (M = 3.47, SE = 0.73) was significantly stronger than in the anger-prime/easy cell (M = 0.90, SE = 0.73), t(71) = 2.47, p < .02, η² = .08. This effect was inversed in the difficult condition. Here, participants primed with sadness showed weaker HR reactivity (M = 1.45, SE = 0.61) than those primed with anger expressions (M = 2.61, SE = 0.56), though the difference was not significant, t(71) = 1.16, p < .25, η² = .02. ANOVAs of SBP and DBP reactivity (see Table 6) found no significant effects (ps > .16)¹⁰.

10 A recent study from our laboratory (Silvestrini & Gendolla, 2011a) had found significant effects of masked affect primes and task difficulty on SBP that were partly determined by effects on total peripheral resistance (TPR) in the vasculature. Given that the present study did not find any significant effects on SBP or DBP, TPR effects were most unlikely. Indeed, calculation of TPR (in dynes second per centimeter to the 5th power) based on measures of cardiac output (Cardioscreen system) and mean arterial pressure

85 Figure 8. Means and standard errors of heart rate reactivity (in beats/min) during task performance.

Table 6. Means and Standard Errors (in Parentheses) of Blood Pressure Reactivity During Task Performance.

Sadness Primes Anger Primes

Easy Difficult Easy Difficult

SBP 5.43

(1.04)

2.78 (0.81)

3.51 (1.10)

3.01 (1.36)

DBP 0.87

(0.21)

0.76 (0.25)

0.62 (0.30)

0.48 (0.23)

Note: SBP = systolic blood pressure (in mmHg); DBP = diastolic blood pressure (in mmHg).

(Dinamap monitor) found neither TPR baseline differences (ps .09; average M = 966.42, SE = 23.39) nor manipulation effects on TPR reactivity (ps .52; average M = 10.77, SE = 7.20).

86 II.3.4.c. Task Performance

Two X 2 ANOVAs of reaction times (in milliseconds) for correct responses and the percentage of correct responses in the task found only significant difficulty main effects, indicating a successful task difficulty manipulation. Reaction times for correct response were shorter in the easy condition (M = 859.81, SE = 32.76) than in the difficult condition (M = 1104.74, SE = 31.43), F(1,71) = 29.25, p < .001, η² = .29, (other ps >

.81). Likewise, the percentage of correct responses was higher in the easy condition (M = 98.75, SE = 0.42) than in the difficult condition (M = 90.41, SE = 1.11), F(1,71) = 45.55, p < .001, η² = .39 (other ps > .52).

II.3.4.d. Affect Ratings

As in our previous studies, we summarized the two positive affect and the two reverse-coded negative affect items of the UWIST scale to mood sum scores for the measures taken before and after the task (Cronbach’s as > .77). Correspondingly, we averaged also the two anger items for both times of measure (Cronbach’s as > .59). We then created average scores to obtain comparable values of both scales. A 2 (prime) X 2 (difficulty) X 2 (time) mixed model ANOVA of the mood scores found only a significant main effect of time, F(1,71) = 11.43, p < .001, η² = .14, due to higher scores before (M = 5.51, SE = 0.11) than after the task (M = 5.20, SE = 0.13). No other effect approached significance (ps > .39). A 2 X 2 X 2 ANOVA of the anger scores revealed a significant difficulty X time interaction, F(1,71) = 8.72, p < .004, η² = .11, (other ps > .09). Focused comparisons found no anger differences between the easy and difficult conditions before the task (p < .52; average M = 1.38, SE = 0.11). After the task, anger was marginally higher in the difficult (M = 1.76, SE = 0.17) than in the easy condition (M = 1.38, SE = 0.11), F(1,71) = 3.34, p < .08, η² = .05. We additionally tested with ANCOVAs for possible significant associations between the post-task affect scores and the reactivity scores of PEP and HR, on which we had found significant manipulation effects. None of these associations was significant (ps > .30), and the above reported prime X difficulty interaction effects remained significant (Fs > 7.14, ps < .009).

87 II.3.4.e. Task Ratings

Participants’ ratings of task difficulty, ability (reverse-coded), and effort intensity were highly correlated (Cronbach’s a > .83) and thus combined to an averaged subjective demand index. A 2 X 2 ANOVA of this index revealed only a significant difficulty main effect, reflecting again a successful difficulty manipulation, F(1,71) = 48.89, p < .001, η²

= .41, (other ps > .36). In the easy condition, reported demand was lower (M = 2.27, SE = 0.14) than in the difficult condition (M = 3.99, SE = 0.19). No significant effect emerged on the importance of success ratings (ps > .15; average M = 5.31, SE = 0.16).

II.3.4.f. Funnel Debriefing and Prime Recognition Test

In the funnel debriefing procedure, 71.11% of the participants reported spontaneously to have seen faces when the experimenter asked to describe a trial of the d2 task. However, only 24.40% of these participants were able to differentiate the faces’

gender, and only one participant reported having seen an emotional expression of the faces. Nobody guessed a link between the faces and effort mobilization. In the prime recognition test, participants’ average recognition rate was on the chance level (M = 49.01%, SE = 3.27), and a 2 X 2 ANOVA found no significant differences between the conditions (all ps > .72).

88 II.3.5. Discussion

As predicted, masked affect primes processed during the performance of a short-term memory task moderated the impact of objective task difficulty on PEP reactivity, our primary and theory based dependent variable referring to mental effort. The observed crossover interaction pattern indicates that the anger and sadness primes had different effects on the two administered difficulty levels, supporting the idea that affect primes’

effects on effort mobilization are emotion category-specific rather than valence specific.

When the task was objectively easy, PEP response was lower in the anger-prime condition than in the sadness-prime condition, which was anticipated because the level of experienced task demand during performance was expected to be higher with the sadness primes than with the anger primes. By contrast, when the task was objectively difficult, PEP response was stronger in the anger-prime condition than in the sadness-prime condition. This was predicted because, in comparison with sadness primes, anger primes should set subjective demand during performance to a high but possible level, while the sadness primes should lead to the experience of too high demand, resulting in disengagement. These effects of the anger primes are compatible with those of happiness primes reported by Silvestrini and Gendolla (2011c) and further support the idea that the motivational effects of anger largely resemble those of positive emotions (see Carver &

Harmon- Jones, 2009).

In contrast to the study by Silvestrini and Gendolla (2011c) on the joint impact of happiness versus sadness primes and task difficulty on cardiovascular response, the present experiment found a significant prime X difficulty interaction on HR reactivity, but no significant effects on SBP. The lack of effects on SBP is not problematic. Effort-related SBP responses in previous studies were explained by the systematic impact of cardiac contractility on SBP (Wright, 1996). However, besides this systematic impact, SBP also relies on vascular resistance and can be masked by it. Thus, finding predicted effects on PEP without finding effects on SBP or DBP is not surprising, because PEP is the much purer index of ß-adrenergic impact on the heart. The present HR effect is not without precursors (e.g., Bongard & Hodapp, 1997; Eubanks et al., 2002; Gendolla &

Richter, 2005; Obrist, 1981; Wright, Williams, & Dill, 1992). However, given that a number of other studies have failed to find performance-related HR effects, we had assessed them without specific predictions. Cognitive tasks usually evoke only relatively

89 small changes in HR, which are likely to rely on parasympathetic withdrawal rather than sympathetic discharge (cf. Berntson, Cacioppo, & Quigley, 1993; Brownley, Hurwitz, &

Schneiderman, 2000). However, apparently, the present manipulations only evoked significant cardiac effects (PEP, HR) that rely on ß-adrenergic impact, supporting Wright’s (1996) integrative analysis.

As in our previous affect priming studies, the prime recognition rates in the present experiment were on the chance level, suggesting that participants processed the masked facial expressions without awareness of their affective content. Moreover, the prime effects occurred without any effects on consciously experienced mood. Although zero effects have to be interpreted with great caution, this makes it at least not very likely that the affect primes had direct “feeling-as-information” effects on participants’

difficulty appraisals, as shown for conscious moods (see Gendolla & Brinkmann, 2005).

Additionally, the present lack of effects on blood pressure—which are typical for anger—

speaks against the possibility that the anger primes made participants angry (see Kreibig, 2010). Moreover, Bongard, Pfeiffer, Al’Absi, Hodapp, and Linnenkemper (1997) investigated the cardiovascular effects of anger during effortful performance of a cognitive task and found that a provocation led to intensified feelings of anger and additional responses of HR and DBP. This pattern was not evident in the present anger-prime condition. Affect anger-primes and task difficulty produced a crossover interaction effect rather than two main effects of task difficulty and prime, which would be suggested by Bongard et al., (1997).

As outlined earlier (Gendolla & Silvestrini, 2011), we explain affect primes’

systematic impact on effort-related cardiovascular response without referring to effects on conscious feelings or the elicitation of full-blown emotions. Accordingly, masked affective stimuli can influence evaluative judgments and behavior through the activation of mental concepts (see Niedenthal, 2008; Zemack-Rugar et al., 2007). Being activated in the context of task performance, this knowledge—happiness and anger are associated with ease while sadness is related to difficulty—influences the experience of task demand

“online” during performance, which in turntakes effect on effort intensity, as outlined in the principles of motivational intensity theory (see Brehm & Self, 1989; Wright & Kirby, 2001). However, in contrast to our previous studies (Gendolla & Silvestrini, 2011;

Silvestrini & Gendolla, 2011c), the measures of subjective task demand after performance

90 indicated only a highly successful task difficulty manipulation, but no significant effect of the affect primes. We attribute this to measurement error, which is explicable by the fact that the demand measure after performance suffered from a number of biases that are typical for retrospective measures (see Robinson & Clore, 2002).

Moreover, as in the study by Silvestrini and Gendolla (2011c), but in contrast to experiments investigating affect primes’ effects on effort without task difficulty manipulations (Gendolla & Silvestrini, 2011; Lasauskaite, Gendolla, & Silvestrini, 2012), the primes had no effects on task performance. However, it has to be considered that the link between effort and performance is complex. Performance depends on effort, ability, and strategy use, rather than on effort alone (Locke & Latham, 1990). Moreover, effort has the function to compensate for obstacles and difficulties in the goal striving process (Hockey, 1997). If the primes have affected subjective task demand, the higher effort in the subjectively difficult sadness-prime/easy and anger-prime/difficult conditions could have had the effect of equalizing performance differences, resulting in the observed zero effect.

In summary, the here-reported moderation of task difficulty’s impact on PEP and HR responses by affect primes supports our idea that the primes influenced effort intensity by influencing experienced demand during task performance, as also shown for other psychological variables, such as ability beliefs (Wright & Dismukes, 1995), fatigue (Wright, Martin, & Bland, 2003), mood (Gendolla & Brinkmann, 2005), and individual differences in extraversion (Kemper et al., 2008) or depression (Brinkmann & Gendolla, 2008). The present findings show that these prime effects are emotion category-specific

In summary, the here-reported moderation of task difficulty’s impact on PEP and HR responses by affect primes supports our idea that the primes influenced effort intensity by influencing experienced demand during task performance, as also shown for other psychological variables, such as ability beliefs (Wright & Dismukes, 1995), fatigue (Wright, Martin, & Bland, 2003), mood (Gendolla & Brinkmann, 2005), and individual differences in extraversion (Kemper et al., 2008) or depression (Brinkmann & Gendolla, 2008). The present findings show that these prime effects are emotion category-specific