Study 1: Locus of control and punishment anticipation

The first study aimed at investigating a specific mechanism that is expected to have an important influence on depressed individuals’ behavior during punishment anticipation: locus

118 Partie empirique: Studies 5 and 6: Mechanisms of control. This quasi-experimental study compared two groups (dysphorics vs. nondysphorics) during anticipation. In accordance with findings from previous studies (Franzen & Brinkmann, 2015c), our first hypothesis suggests that (1) dysphoric individuals would report a normal motivation to avoid the punishment, and that (2) they would show a reduced cardiovascular response during punishment anticipation. Our second and main hypothesis suggests that locus of control would mediate the link between dysphoria and effort mobilization. Specifically, we postulate that dysphoric individuals would mobilize less effort during punishment anticipation because their locus of control is more external. In contrast, we postulate that, because nondysphoric individuals’ locus of control is more internal, they would mobilize more effort in order to avoid the punishment. Stated differently, nondysphoric individuals believe in their capacities to avoid the punishment and therefore mobilize their efforts, whereas dysphoric individuals believe that effort mobilization is futile because they do not have any control anyway.

5.2.1. Method

Participants. The final sample consisted of 39 university students, 32 women and 7 men aged from 18 to 49 years old (M = 23.75, SD = 6.13). Recruited through flyers on the university blackboards, these participants received 10 Swiss Francs (about 10 USD) for their voluntary and anonymous participation. Twenty-one participants were located in the lower quartile of a questionnaire assessing depressive symptomatology, a French version of the Center for Epidemiologic Studies – Depression Scale (CES-D; Fuhrer & Rouillon, 1989;

Radloff, 1977) (M = 4.57, SD = 2.73) and were therefore referred to as nondysphorics.

Eighteen participants were situated in the upper quartile of the CES-D (M = 25.39, SD = 6.48) and were referred to as dysphorics.

Preceding the actual experimental session, a total of 101 potential participants answered an online version of the CES-D. If their score on this questionnaire was situated in the lower quartile or in the upper quartile of the distribution, participants were invited to take part in the experimental session via an anonymous code. The CES-D was assessed a second time during the experimental session. From the initial sample of 48 participants invited for the experimental session, only those whose CES-D scores at this second measurement time stayed within the lower (≤ 10) or upper (≥ 16) quartile of the CES-D were retained for analyses (N = 42). Two participants were further excluded because of bad signal quality of our primary physiological recordings (PEP) and another one because his/her cardiovascular reactivity was extremely high (more than 3 standard deviations above the overall mean).

Experimental task and punishment manipulation. Composed of 51 trials, the experimental task was an adapted version of the D2 mental concentration test (Brickenkamp

Partie empirique: Studies 5 and 6: Mechanisms 119

& Zillmer, 1998). For each trial, a fixation cross was presented in the middle of the screen for 500 ms. Then, a picture was presented, which could depict the letter d or the letter p, accompanied by 1 to 4 apostrophes. Then, the picture was masked and the participants had to identify if the picture depicted or not the letter d and if this letter was accompanied or not by exactly 2 apostrophes. If the picture depicted the letter d and was accompanied by 2 apostrophes (i.e., the target stimulus), the participants had to press the "yes" key on the keyboard. If the picture depicted the letter p with 2 apostrophes or the letters d or p with 1, 3, or 4 apostrophes (i.e., the distraction stimuli), the participant had to press the "no" key on the keyboard. After the participants’ response, the message “answer recorded” was presented in the middle of the screen. If the participants had not answered after 3 seconds, the message

“please answer more quickly” appeared in the middle of the screen during 1 second. Then, a new trial began.

According to the predictions of motivational intensity theory (Brehm & Self, 1989; for a detailed discussion see Richter, 2013) and in order to create a task with unclear difficulty, the required performance standard was revealed only at the end of the task. Moreover, participants were told only about the general procedure of the task, but they were not given any details, like the duration of the stimulus presentation (i.e., the difficulty) or the total number of trials. In fact, there were 51 trials with a varying stimulus presentation time from 66 to 333 ms. The total time of the task was 4.84 min.

Concerning the punishment manipulation, participants were informed that they had an initial credit of 10 Swiss Francs (about 10 USD). They were also told that if their performance was lower than a performance standard to be revealed later, they would lose this credit at the end of the experiment. An individual performance standard was created for all participants unbeknownst to them. This individual performance standard was computed by the computer program by adding 2 to each participant's number of correct responses, so that all participants lost their initial credit. Because the present study exclusively focused on the anticipatory component, the creation of an individual performance standard was not relevant. We did so for the comparability of the procedure of the two studies. In Study 2, where the affective responses during reward consumption were assessed, an individual manipulation of the performance standard was indispensable.

Cardiovascular measures. In order to measure responsiveness to punishment during anticipation, cardiovascular measures were collected noninvasively during two specific periods: habituation and task performance. PEP (in milliseconds [ms]) and HR (in beats per minute [bpm]) were measured noninvasively using a Cardioscreen® 1000 haemodynamic monitoring-system (medis, Ilmenau, Germany) (for a validation study see Scherhag, Kaden, &

Kentschke, 2005). This system continuously samples electrocardiogram (ECG) and

120 Partie empirique: Studies 5 and 6: Mechanisms impedance cardiogram (ICG) signals at 1000 Hz. Four dual gel-pad sensors (medis-ZTECT^TM) were placed on each side of the base of the participant’s neck and on each side of the thorax along the mid axillary line at the level of the xiphoid. Systolic blood pressure (SBP, in millimeters of mercury [mmHg]) and diastolic blood pressure (DBP, in millimeters of mercury [mmHg]) were measured noninvasively using a Dinamap Procare 300 monitor (GE Medical Systems, Information Technologies Inc., Milwaukee, WI). A blood pressure cuff was placed over the brachial artery above the elbow of the participants' nondominant arm and automatically inflated every minute.

Performance measures. In order to assess anticipatory punishment responsiveness on a behavioral level, performance outcomes of the d2-concentration task were considered:

the number of correct responses (out of 51 trials) and the global reaction time for all trials during task performance.

Self-reported motivation. In order to measure the subjective motivation to avoid the punishment, participants indicated their motivation to avoid the punishment (“To what extent are you motivated to avoid the loss of the 10 Swiss Francs?”) on a visual analogue scale ranging from 0 (not motivated) to 100 (very motivated).

Depression questionnaire. For assessing the severity of depressive symptomatology, the French version of the CES-D (Fuhrer & Rouillon, 1989) was used. This self-report depression scale is composed of 20 items evaluating the frequency of depressive symptoms during the past week using 4-point scales ranging from 0 (never, very seldom) to 3 (frequently, always). The total score is calculated by summing all items (four reverse-scored items) and can vary from 0 to 60 (Cronbach’s α = .95 during the experimental session).

Locus of control. We measured locus of control with the French version of the Internal, Powerful others, and Chance scales (IPC; Levenson, 1981; Rossier, Rigozzi, & Berthoud, 2002). As a multidimensional modification of Rotter’s internal-external control scale (Rotter, 1966), this self-report scale measures three different dimensions, which are internality (Cronbach’s α = .71), control by powerful others (Cronbach’s α = .72), and control by chance forces (Cronbach’s α = .83). Each of the three scales is composed of 8 items, which are answered on a 6-point Likert scales from 1 (strongly agree) to 6 (strongly disagree). Scores for each scale were calculated by summing all respective items.

Procedure. This study was divided into two parts, an online session and an experimental session. Participants individually answered the online CES-D, and were then, if

Partie empirique: Studies 5 and 6: Mechanisms 121 applicable, invited for the experimental session, which was individual and took about 30 minutes.

The experimental session was conducted using a personal computer and experimental software (Inquisit 3.0, Millisecond Software, Seattle, WA) that presented all instructions and stimuli. The experimenter, who was unaware of both the hypotheses and the experimental conditions of the study, first welcomed the participants and asked them to take a seat and to sign a consent form. Afterwards, the experimenter applied the sensors for assessment of cardiovascular measures, left the room, and monitored the experiment from an outside control room. The participants then answered two questionnaires, the CES-D and the IPC scales, ostensibly for an unrelated questionnaire validation study. When they had finished, the experimenter reentered the room, started the following of the experimental session, and left the room. The participants read general information regarding the study and answered some socio-demographic questions. Next, the participants watched an 8-minutes excerpt of a neutral documentary movie, during which cardiovascular baseline measures were assessed. After this habituation period, task and punishment instructions were given to the participants, who then evaluated their motivation to avoid the punishment (i.e., subjective measure of wanting). Then, participants completed the d2-concentration task for about 5 minutes, during which cardiovascular and performance measures were assessed. When participants had finished the task, they received information about the performance standard, about their own performance score, and they were informed that they lost their initial credit. Finally, the experimenter reentered the room and removed the blood pressure sensor and the electrodes. Participants were thanked and debriefed.

Data analyses. For the measuring of PEP (computed as the time interval between ECG R-onset and ICG B-point; Berntson, Lozano, Chen, & Cacioppo, 2004), the ICG’s first derivative (ICG dZ/dt signal) was ensemble averaged over periods of 60 seconds and synchronized with the ECG signal. The ECG R-onset and the ICG B-point (the indicator of the opening of the aortic valve) were automatically detected by LabVIEW-based software (National Instruments, Austin, TX) developed in our laboratory (Richter, 2009). R-onset and B-point were then visually inspected by two independent raters and modified if necessary (see Sherwood et al., 1990). Because the inter-rater agreement was high (intraclass correlation ICC(2,1) = .97, Shrout & Fleiss, 1979), the arithmetic mean of both raters’ PEP values was used for statistical analyses. HR (in beats per minute) was determined by means of the same software that detects and counts R-peaks in the ECG signal, which were visually confirmed afterwards.

PEP, HR, SBP, and DBP baseline scores were created by averaging the last 4 minutes of the habituation period (Cronbach’s αs > .95). Arithmetic means of PEP, HR, SBP, and DBP measures assessed during the 5-minute task performance constituted task scores (Cronbach’s

122 Partie empirique: Studies 5 and 6: Mechanisms αs > .95). Cardiovascular reactivity scores were then computed for each participant and each cardiovascular parameter as the difference of task scores minus respective baseline scores (see Kelsey et al., 2007; Llabre et al., 1991). In order to compare dysphoric and nondysphoric participants on all physiological, behavioral, and self-report measures, independent samples t-tests were performed.

For the mediation hypothesis, three mediation models were computed using the PROCESS macro for SPSS developed by Preacher and Hayes (Preacher & Hayes, 2008): the direct effect procedure, the nonparametric bootstrapping procedure, and the Sobel test.

Concerning the direct effect procedure and according to Baron and Kenny (1986), a variable is considered a mediator when the following conditions are met: The effect of the independent variable on the mediators (Path A) must be significant, the effect of the mediators on the dependent variable controlling for the independent variable (Path B) must be significant, the total effect of the independent variable on the dependent variable (Path C) must be significant, and the previously significant effect of the independent variable on the dependent variable must be no longer significant when the mediators are controlled for (Path C'). Both the Sobel test (Sobel, 1982) and the nonparametric bootstrapping procedure (Preacher & Hayes, 2004) determine the significance of the indirect effect of the predictor variable on the outcome variable through its effects on the mediator. The results of the nonparametric bootstrapping procedure are based on 5000 bootstrapped re-samples, and 95% confidence intervals were computed. The indirect effect of the bootstrapping procedure is considered significant if the upper and lower bounds of the confidence intervals do not contain zero. Parallel multiple mediation regression analyses were used in order to simultaneously examine the mediating effect of the three ICP scales (i.e., internality, control by powerful others and control by chance forces) on the relationship between dysphoria (dichotomous predictor variable) and effort mobilization (i.e., PEP reactivity; outcome variable).

5.2.2. Results

Preliminary analyses. Independent samples t-tests revealed no significant group differences on none of the cardiovascular baseline measures, ts < 1.35, ps > .19, showing that dysphorics and nondysphorics did not significantly differ on none of the cardiovascular baseline measures. Means and standard errors of the baseline measures for PEP, HR, SBP, and DBP are presented in Table 9.

Partie empirique: Studies 5 and 6: Mechanisms 123 Table 9

Means and Standard Errors of Cardiovascular Baseline in Study 1

M SE

PEP HR SBP DBP PEP HR SBP DBP

Nondysphorics 99.68 72.73 101.29 58.08 2.45 2.33 2.52 1.21 Dysphorics 94.15 72.39 101.78 58.29 3.48 2.03 1.17 0.79

Note. PEP is indicated in milliseconds, HR is indicated in beats per minute, and SBP and DBP are indicated in millimeters of mercury.

Punishment anticipation analyses. Regarding anticipatory punishment responsiveness, analyses revealed a significant result for the PEP, our main cardiovascular dependent variable, t(37) = 2.57, p = .01, ηp2 = .15. As expected, nondysphorics’ PEP reactivity (M = -6.89, SE = 1.75) was higher than dysphorics’ PEP reactivity (M = -1.45, SE = 1.03), which confirms our hypothesis (see Figure 10A). However, the t-tests for HR, SBP, and DBP reactivity were not significant, ts < 1.19, ps > .24 (see Table 10 for means and standards errors of these cardiovascular measures).

Table 10

Means and Standard Errors of Cardiovascular Reactivity in Study 1

M SE

HR SBP DBP HR SBP DBP

Nondysphorics 4.21 6.73 4.34 0.76 1.10 1.00

Dysphorics 4.07 4.78 3.62 0.81 1.21 0.76

Note. HR is indicated in beats per minute and SBP and DBP are indicated in millimeters of mercury.

Regarding the behavioral measure during task performance, the result showed a marginally significant t-test for the correct responses, t(37) = -2.00, p = .05, ηp2 = .10. As illustrated in Figure 10B, this result indicates that dysphoric individuals gave less correct responses (M = 42.17, SE = 1.99) than did nondysphoric individuals (M = 46.14, SE = 0.70).

124 Partie empirique: Studies 5 and 6: Mechanisms (nondysphoric group: M = 661.80, SE = 24.91; dysphoric group: M = 762.79, SE = 71.25).

Concerning the subjective motivation to avoid the punishment, the t-test revealed no significant group difference, t(37) = -1.67, p = .10 (see Figure 10C), indicating the expected similar level of subjective motivation in both groups (nondysphoric group: M = 86.71, SE = 3.27; dysphoric group: M = 79.61, SE = 2.55).

Figure 10

Means and standard errors of (A) pre-ejection period reactivity, (B) number of correct responses, and (C) self-reported wanting during punishment anticipation in Study 1

Locus of control. The analyses concerning the three dimensions of locus of control revealed a significant group difference for the internal locus of control, t(37) = -4.83, p < .001, ηp2 = .38, indicating that nondysphoric individuals (M = 37.14, SE = 0.97) had a higher internal locus of control than dysphoric individuals (M = 29.33, SE = 1.33) (see Figure 11A). Analyses also revealed a significant group difference for the powerful others locus of control, t(37) =

A B

C

Partie empirique: Studies 5 and 6: Mechanisms 125

4.09, p < .001, ηp2 = .31, as illustrated in Figure 11B. This result demonstrates that the powerful others locus of control was lower in the nondysphoric group (M = 13.09, SE = 1.65) than in the dysphoric group (M = 22.17, SE = 1.42). Finally, analyses revealed a significant group difference for chance locus of control, t(37) = 2.51, p = .02, ηp2 = .14, indicating that the nondysphoric group (M = 17.14, SE = 2.25) reported a lower chance locus of control than the dysphoric group (M = 24.50, SE = 1.77) (see Figure 11C). The group differences on all three scales thus conform to our predictions.

Figure 11

Means and standard errors of (A) internal, (B) powerful others, and (C) chance locus of control in Study 1

Mediation analyses. Concerning the parallel multiple mediation analyses, we first considered the direct effect procedure. As illustrated in Table 11, the conditions to consider a variable as a mediator suggested by Baron and Kenny (1986) were all met for two dimensions of locus of control, internality and chance. These results indicate that the effect of dysphoria

A B

C

126 Partie empirique: Studies 5 and 6: Mechanisms on effort mobilization was fully mediated by internality and control of chance forces. In contrast, the conditions recommended by Baron and Kenny were not entirely met for control by powerful others, because Path B was not significant. This result shows that control by powerful others could not be considered a mediator of the relationship between dysphoria and effort mobilization. Regarding the Sobel test analyses, results show a marginally significant mediating effect of internality, but no significant mediating effects of the two other dimensions of locus of control, control by powerful others and control by chance forces. Finally, results of the bootstrapping method show a significant mediating effect of internality and control of chance forces because zero was not contained in the 95% confidence interval. However, the results for the third dimension of locus of control, control by powerful others, show no significant effect with the bootstrapping method, because zero was contained in the 95% confidence interval.

Table 11

Impact of three mediators (internality, powerful others, chance) between dysphoria (predictor variable) and effort mobilization (outcome variable) with unstandardized regression coefficients (β) of Paths A, B, C, and C', Sobel test statistics, and bootstrapping procedure statistics in Study 1

Note. CI = confidence intervals; The nonparametric bootstrapping procedures are based on 5000 bootstrapped re-samples

In a multiple mediation model, it is possible that the effect of the mediators on the dependent variable (Path B) is reduced to the degree to which the mediators are correlated (Preacher & Hayes, 2008). Because the control by powerful others was correlated to the control of chance forces (r = .59, p < .001) and to internality (r = -.44, p < .01), these correlations could explain the non-significant effect of control by powerful others on the relationship between dysphoria and effort mobilization. Thus, we additionally performed a simple mediation analysis for this dimension. Concerning the direct effect procedure, the results show that Paths

Partie empirique: Studies 5 and 6: Mechanisms 127 A (β = 9.07, SE = 2.22, p < .001), B (β = .41, SE = .14, p <.01), and C (β = 5.44, SE = 2.12, p

= .01) were significant, while Path C’ (β = 1.72, SE = 2.33, p = .47) was not. These results demonstrate that the conditions suggested by Baron and Kenny (1986) to consider control by powerful others as a mediator are all met. The Sobel test revealed a significant indirect effect (z = 2.29, p = .02), as did the nonparametric bootstrapping procedure (CI 0.9742 – 8.1485).

5.2.3. Brief discussion

The aim of Study 1 was to demonstrate the mediating role of locus of control for the relationship between dysphoria and effort mobilization. Firstly, results confirmed previous studies (e.g., Franzen & Brinkmann, 2015c) by showing that dysphoric individuals reported similar motivation to avoid the punishment but had weaker PEP reactivity during task performance. Secondly, results are in line with past research (Benassi et al., 1988) by showing lower internal but higher external locus of control in dysphoria. Finally, the direct effect procedure and the bootstrapping method of the multiple mediation analyses revealed a mediating effect of two dimensions of locus of control: internality and chance. There was no effect of the third dimension of locus of control, control by powerful others. However, the simple mediation analysis for this dimension revealed a mediating effect with the direct effect procedure, the bootstrapping method, and the Sobel test.

Taken together, these results suggest that locus of control can be considered as a mediator of the relationship between dysphoria and effort mobilization. The present study demonstrates that dysphoric individuals do want to avoid the punishment, as evidenced by self-reports. However, they do not believe to have control over the consequences of their actions (i.e., an external locus of control), which leads them to mobilize less effort to avoid the punishment.