4. Studies 3 and 4

4.1. Experiment 1

After being presented with video excerpts to manipulate mood, participants performed a mental concentration task with the instruction to regulate their effort mobilization according to either one of two effort-rules. Cardiovascular activity was assessed during habituation, the mood inductions, and task performance. During performance, we expected higher cardiovascular reactivity (especially SBP) in a negative mood than in a positive mood in the enough-rule condition. By contrast, in the enjoy-rule condition cardiovascular reactivity was anticipated to be stronger in a positive mood than in a negative mood. We did not anticipate any mood effects on cardiovascular reactivity during the mood inductions.

4.1.1. Method Participants and design

Forty-three university students with various majors (18 women, 25 men, mean age 22 years) were randomly assigned to the four cells of a 2 (mood: negative vs. positive) x 2 (effort-rule: enjoy-rule vs.

enough-rule) between-persons design. The distribution of women and men were balanced between the conditions. Participation was voluntary and anonymous.

Apparatus and physiological measures

Cardiovascular measures were assessed with a computer-aided monitor (Par Electronics Physioport III, Berlin, Germany) that uses oscillometry to determine SBP (in millimeter mercury [mmHg]), DBP (mmHg), and HR (in beats per minute [bpm]). For this purpose, a blood pressure cuff was placed over the brachial artery above the elbow of the participants’ non-dominant arm. The cuff was automatically inflated in 2 min intervals and the obtained data were stored on the system’s hard disk.

Experimenter and participants were ignorant of any cardiovascular values assessed during the experiment.

Procedure

The experiment was run in individual sessions. Participants were informed that they would work on two different tasks and that their cardiovascular activity would be assessed during the session.

Participants learned that the first “task” was watching two short video excerpts, which they should compare and rate afterwards. After application of the blood pressure cuff participants answered some biographical questions and inquiries about their media consumption to maintain the cover story. Then participants rated their current mood using eight adjectives with positive (happy, joyful, contented, cheerful) and negative (sad, frustrated, depressed, dissatisfied) hedonic tone of the UWIST scale (Matthews, Jones, & Chamberlain, 1990). For each adjective, participants rated on a scale from not at all (0) to very much (6) how far it corresponded to their current mood (“Right now, I am feeling …”). Then the procedure continued with the presentation of the two video excerpts.

Cardiovascular baselines measures and mood manipulation. The first video excerpt was presented to all participants. It was an 8 min hedonically neutral film showing a train ride. This video served to determine participants’ cardiovascular baseline values—we took four cardiovascular measures in 2 min intervals, starting with the film onset. The second video excerpt was presented to manipulate mood. The excerpts were chosen on the basis of previous studies from our lab that already validated their efficiency (e.g., Gendolla & Krüsken, 2002a; Silvestrini & Gendolla, 2007). Participants in the positive mood condition watched a funny excerpt from the movie “Naked Gun 2 1/2”, while participants in the negative mood condition were presented with the depressing end of the movie “Love Story.” During the 8 min presentation of the video excerpts, 4 cardiovascular measures were taken in 2-min intervals, starting at the onset of the video. After the mood inductions, participants answered various questions referring to characteristics of both films to distract them from the real purpose of the video

presentation. Participants then rated their current mood again using the eight adjectives of the UWIST scale in order to obtain a post-manipulation mood measure.

Task performance. After the mood induction participants received the written instructions for a paper-pencil version of the “d2 mental concentration task” (Brickenkamp, 1981). Random sequences of ds and ps were presented in 14 rows on a sheet of paper. Above and below of each letter were either 1, 2, or no apostrophes. Participants learned that they should mark within 5 min as many ds that carried exactly 2 apostrophes as they could.

Participants in the enjoy-rule condition were instructed to ask themselves during performance the question “Do I enjoy task performance?” and to modify their effort investment according to the answer.

Specifically, participants in this condition learned that they should stay on their actual level or invest more effort if they were enjoying the task and that they should reduce effort if they did not. By contrast, participants in the enough-rule condition were informed that they should guide their effort mobilization by asking themselves “Do I already invest enough effort?” Furthermore, they learned that they should increase effort if the answer to this question was “no”, whereas they should reduce effort if the answer was “yes”.

After participants had read the task instructions, they performed one practice line of the mental concentration task and started with the 5 min of task performance. At the end of the 1st, 2nd, and the 4th minute of task performance, the experimenter orally reminded participants of their respective effort-rule. Three cardiovascular measures were taken during performance (at task onset, 2 min and 4 min after task onset). Finally, participants were interviewed with regard to suspicion and debriefed.

4.1.2. Results

Mood manipulation check

Mood baseline and post manipulation scores were created by adding the reversed scores of the negative items to the scores of the positive items (Cronbach’s αs > .80 for both measures). We then created mood change scores by subtracting the mood baseline scores from the post manipulation scores. A 2 (mood) x 2 (effort-rule) between-persons ANOVA of the mood baseline scores found no significant differences between the conditions (ps > .72, average M = 33.91, SE = 0.91). However, a 2 x 2 between-persons ANCOVA of the mood change scores, using the mood baseline scores as covariate, revealed a significant association between baselines and change scores, F(1, 38) = 5.50, p < .03, and the

expected mood main effect, F(1, 38) = 21.34, p < .001. In support of a successful manipulation, mood was elated in the positive mood condition (M = 1.95, SE = 0.79) and depressed in the negative mood condition (M = -3.17, SE = 0.77) after participants had watched the video excerpts. No other effect approached significance (ps > .40).

Cardiovascular baselines

The arithmetic mean of all four HR baseline measures constituted our HR baseline scores (Cronbach’s α = .89). SBP and DBP baseline scores were created of the last three measures (Cronbach’s αs > .88) because the first measure of both parameters significantly differed from the other three measures (ps < .04). Two (mood) x 2 (effort-rule) between-persons ANOVAs of the scores did not show any significant effect (ps > .14). Cell means and standard errors appear in Table 5.

Table 5. Cell Means and Standard Errors (in Parentheses) of the Cardiovascular Baseline Values (Experiment 1).

enjoy-rule enough-rule

Negative mood Positive mood Negative mood Positive mood

SBP 113.98 112.71 115.77 111.35

(1.92) (2.69) (2.61) (3.24)

DBP 72.80 72.74 71.76 72.13

(1.71) (2.33) (2.10) (2.19)

HR 79.63 77.11 76.09 82.00

(3.08) (2.30) (2.20) (3.59)

Note: DBP: diastolic blood pressure; HR: heart rate. Units of measure are millimeters of mercury for DBP, beats per minute for HR.

Cardiovascular reactivity

Change (delta) scores (Llabre, Spitzer, Saab, Ironson, & Schneiderman, 1991) were computed for each participant by subtracting the baseline values from the averages of values obtained during the mood induction and the task performance periods. To control for biases due to the law of initial values, preliminary 2 (mood) x 2 (effort-rule) x 2 (time) ANCOVAs checked for associations between baseline values and reactivity scores. These analyses found no reliable associations for SBP (ps > .32) and HR (ps >

.09). However, there was a significant association between the DBP baselines and reactivity scores, F(1,

38) = 8.76, p < .04, that was further qualified by a Covariate x Time interaction, F(1, 38) = 49.92, p < .001.

Therefore we adjusted the DBP reactivity scores with regard to the baseline values in the further analysis.

SBP reactivity. Cell means and standard errors appear in Figure 9. The 2 (mood) x 2 (effort-rule) x 2 (time) mixed model ANOVA of systolic reactivity, our primary dependent measure, revealed a significant main effect of time, F(1, 39) = 30.22, p < .001, due to stronger reactivity during task performance (M = 2.71, SE = 0.88) than during the mood inductions (M = -2.46, SE = 0.62). Most relevant, the three-way interaction was also significant, F(1, 39) = 7.06, p < .01, in absence of further significant effects (all other ps > .10). A 2 (mood) x 2 (effort-rule) between persons ANOVA of systolic reactivity during the mood inductions revealed no significant effects (all ps > .20). But a 2 x 2 ANOVA of SBP changes during task performance found the anticipated interaction, although this effect was only marginally significant, F(1, 39) = 3.90, p < .06, (all other ps > .17). However, focused cell contrasts (one-tailed due to our directed theory-driven predictions) found trends to the anticipated stronger SBP reactivity in the positive-mood/enjoy-rule cell (M = 3.26, SE = 2.37) than in the negative-positive-mood/enjoy-rule condition (M = -0.18, SE = 2.02), t(39) = 1.45, p < .07. As anticipated, the opposite pattern occurred in the enough-rule condition. Here, reactivity was lower in the positive-mood cell (M = 2.22, SE = 2.57) than in the negative-mood cell (M = 5.50, SE = 2.40), t(39) = 1.35, p < .09.

DBP and HR reactivity. Cell means and standard errors appear in Table 6. The analysis of baseline-adjusted DBP reactivity did not reveal any significant effect (ps > .07). A 2 (mood) x 2 (effort-rule) x 2 (time) mixed model ANOVA of HR reactivity did only reveal a significant effect of time, F(1, 39) = 25.63, p

< .001, reflecting stronger reactivity during task performance (M = 6.29, SE = 1.32) than during the mood inductions (M = -0.68, SE = 0.97), (all other ps > .16).

Task performance

Task performance was analyzed in terms of the total number of performed stimuli, and the net performance index (i.e., detected symbols minus errors). However, a 2 (mood) x 2 (effort-rule) between-persons ANOVA found no significant effects on any of these performance indices (all ps > 26). By average, participants performed M = 423.00 (SE = 10.61) letters and made M = 12.74 (SE = 1.88) errors.

A: Mood induction phase

B: Task performance phase

Figure 9. Cell means and standard errors of systolic blood pressure (SBP) reactivity during the mood induction (top panel) and task performance (bottom panel) periods (Experiment 1).

Enjoy-rule

SBP reactivity (mmHg)

-4 -2 0 2 4 6

8 Positive mood

Negative mood

Enough-rule Enjoy-rule

Enjoy-rule

SBP reactivity (mmHg)

-4 -2 0 2 4 6

8 Positive mood

Negative mood

Enjoy-rule Enough-rule

Table 6. Cell Means and Standard Errors (in Parentheses) of the DBP and HR reactivity (Experiment 1).

enjoy-rule enough-rule

Negative mood Positive mood Negative mood Positive mood

Mood inductions

DBP 1.08 -0.71 -0.83 -1.13

(1.12) (1.15) (0.96) (1.16)

HR 1.30 -0.36 -1.36 -2.45

(1.45) (1.50) (1.58) (3.11)

Task performance

DBP 1.95 5.68 5.85 3.87

(2.42) (1.95) (2.50) (1.71)

HR 4.77 6.16 9.45 4.63

(2.26) (2.60) (3.57) (1.78)

Note: DBP: diastolic blood pressure; HR: heart rate. Units of measure are millimeters of mercury for DBP, beats per minute for HR.

4.1.3. Discussion

As predicted, this study revealed a significant three-way interaction effect between mood, effort-rule, and time on SBP reactivity—our primary dependent variable. In further support of the MBM idea that moods themselves are not motivational states (Gendolla, 2000) the efficiently manipulated positive and negative moods had no impact on cardiovascular arousal during the mood inductions. However, in the context of the mental concentration task, the effort mobilization rule participants were instructed to apply moderated moods’ effect on resource mobilization. Although the interaction between mood and effort-rule on SBP reactivity was only marginally significant in the follow-up analysis of systolic reactivity during task performance, the present study brought the first empirical evidence for the moderating effect of an “enjoyment rule” on effort intensity and extends the research of Martin et al. (1993) that dealt with mood effects on persistence: When participants asked themselves if they enjoyed their performance, SBP reactivity was stronger in a positive mood then in a negative mood. But when they asked themselves if they invested enough effort, systolic reactivity was stronger in a negative mood than in a positive mood. DBP and HR reactivity were less sensible for the manipulations of mood and

effort-rule. This is, however, not surprising due to the physiological processes underlying these cardiovascular indices, as discussed above.

Although systolic reactivity during task performance described the anticipated pattern in support of a context-dependent mood impact on effort mobilization, we have to acknowledge that the focused cell comparisons did not attain statistical significance. One possible reason for the relative weak effects could be the interaction between experimenter and participants in the present study. The experimenter orally interrupted participants’ three times during task performance to remind them of the effort-rule they should apply. These interruptions by the experimenter may have resulted in a general tendency to disengage that flattened the mood effect on effort mobilization (cf. Klinger, 1975).

Thus, this study calls for a conceptual replication with a procedure that minimizes contact between experimenter and participants during task performance.

Dans le document Mood and mental effort : informational mood impact on cardiovascular reactivity and the context-dependency of moods (Page 113-120)