4. Studies 3 and 4

4.3. Experiment 3

To test if we can generalize the most important effect of the first two experiments—stronger effort-related cardiovascular reactivity in a positive mood when effort is adjusted according to an enjoy-rule—we conceptually replicated the enjoy-rule condition of Experiments 1 and 2 with a task focusing on another aspect of cognitive performance – memory.

4.3.1. Method Participants and design.

Twenty-six university students (all women, average age 27 years) received 10 Swiss Francs (about 10 US$) for their anonymous and voluntary participation. They were randomly assigned to either one of the two cells of a 2 (mood: negative vs. positive) x 1 (effort-rule: enjoy-rule) design.

Apparatus and procedure

The experimental protocol was identical to the enjoy-rule condition of Experiment 2, with the exception that we assessed HR with the blood pressure monitor instead of ECG. The reason was economy since the more sophisticated ECG measures applied in Experiment 2 did not reveal the same reactivity pattern as SBP. After the assessment of biographical data and mood baseline ratings, watching the hedonically neutral film, the mood inductions with the same video excerpts as in the previous two studies, and the post-manipulation mood ratings (7-point UWIST scale) participants received the instructions for a memory task: “In the next 5 minutes you will be presented with a list of letter series, each consisting of 4 letters. Please correctly memorize as many series as you can. You will be asked to note those series you can remember after the five minutes of memorizing.” Then the computer monitor displayed a list of 12 senseless 4-letter series (e.g., ALMP, TSAM, QPTA). After the 5 min of memorizing,

the experimenter re-entered the room and gave a sheet of paper to the participants in order to let them note the series they could remember. The experimental session ended with debriefing, paying, and thanking the participants.

4.3.2. Results

Mood manipulation check

Mood baseline and change scores (Cronbach’s αs > .81) were created as in the previous studies. A preliminary ANOVA of the mood baseline scores did not find any effects (ps > .30, overall M = 18.42, SE = 0.91). An ANCOVA of the mood change scores found a significant association with the mood baseline values, F(1, 26) = 8.34, p < .01, and, most relevant, the anticipated mood main effect, F(1, 24) = 6.69, p <

.02. In support of successful mood inductions, mood was elated in the positive mood condition (M = 2.00, SE = 0.56) and depressed in the negative mood induction (M = -1.46, SE = 1.22) after watching the video excerpts.

Cardiovascular baselines

Cell means and standard errors are shown in Table 10. The averages of the last two cardiovascular measures in the habituation period (hedonically neutral film) constituted the baseline values for SBP, DBP, and HR (Cronbach’s αs > .87).16 There were no baseline differences between the two mood conditions (all ps > .30).

Cardiovascular reactivity

Reactivity scores were created as in the previous studies. Both the mood inductions and task performance averaged change scores for SBP and DBP showed high internal consistency (Cronbach’s αs

> .93). Internal consistency of the HR reactivity scores was considerably lower (mood induction:

Cronbach’s α = .52, task performance: Cronbach’s α > .06). However, exclusion of the last change score of the task performance period resulted in considerably higher consistency (Cronbach’s α = .80).17 Preliminary tests of baseline-reactivity associations with 2 (mood) x 2 (time) ANCOVAs found a Time x Baseline interaction for the HR reactivity, F(1, 23) = 4.39, p < .05. Consequently, the reactivity scores were corrected with regard to the baselines to prevent carry-over or initial values effects (Llabre et al., 1991).

16 We calculated the physiological baseline values from the four last minutes of the habituation period because for all parameters the last two last measures did not differ significantly from one another (ps > .30).

17 Due to measurement errors, the HR the reactivity scores are based on N = 25. Moreover, the omission of the last HR measure during task performance did not change the statistical significance of the results.

Table 10. Cell Means and Standard Errors (in Parentheses) of the Cardiovascular Baseline Values (Experiment 3).

enjoy-rule

Negative mood Positive mood

SBP 102.69 106.85

(3.06) (2.33)

DBP 68.88 71.96

(2.27) (1.84)

HR 80.23 81.35

(2.77) (3.28)

Note: Cell ns = 13. SBP: systolic blood pressure; DBP: diastolic blood pressure; HR: heart rate. Units of measure are millimeters of mercury for SBP and DBP, beats per minute for HR.

SBP reactivity. Cell means and standard errors are depicted in Figure 11. A 2 (mood) x 2 (time) mixed-model ANOVA revealed the expected Time x Mood interaction, F(1, 24) = 5.71, p < .02, in absence of other significant effects (p > .30). Mood had no effect during the mood inductions (p > .80; positive mood: M = 1.15, SE = 1.44; negative mood: M = 0.62, SE = 1.61). But during task performance, SBP reactivity was as expected stronger in a positive mood (M = 4.54, SE = 1.45) than in a negative mood (M

= -0.76, SE = 1.18), F(1, 24) = 8.03, p < .01.

DBP and HR reactivity. The only effect that at least approached significance in the 2 (mood) x 2 (time) ANOVA of DBP reactivity was a time main effect, F(1, 24) = 3.27, p < .08, indicating tendencially stronger reactivity during task performance (M = 2.01, SE = 0.67) than during the mood manipulation (M

= 0.61, SE = 0.68). The mixed model ANCOVA of baseline-adjusted HR change scores found only a main effect of time, F(1, 23) = 6.73, p < .02, reflecting stronger reactivity during task performance (M = 3.94, SE = 1.00) than during mood inductions (M = -4.17, SE = 1.72), in absence of other significant effects (ps

> .50). Cell means and standard errors are presented in Table 11.

SBP reactivity (mmHg)

-2 -1 0 1 2 3 4 5 6

Positive mood Negative mood

Mood induction Task performance

Figure 11. Cell means and standard errors of systolic blood pressure (SBP) reactivity during the mood induction and task performance periods (Experiment 3).

Table 11. Cell Means and Standard Errors (in Parentheses) of the DBP and HR reactivity (Experiment 3).

enjoy-rule

Negative mood Positive mood Mood inductions

DBP 0.48 0.73

(0.84) (1.08)

HR -6.72 -1.62

(2.43) (2.43)

Task performance

DBP 0.69 3.32

(0.97) (0.92)

HR -1.61 1.84

(2.23) (2.23)

Note: Cell ns = 13. DBP: diastolic blood pressure; HR: heart rate. Units of measure are millimeters of mercury for DBP, beats per minute for HR.

Task performance

Cell means and standard errors are presented in Table 12. Comparisons between the two mood conditions found no significant effects, neither regarding the total number of recalled letter series (negative mood: M = 7.62, SE = 0.42, positive mood: M = 8.00, SE = 0.44), p > .53, nor the number of correctly recalled series (negative mood: M = 4.85, SE = 0.71, positive mood: M = 6.15, SE = 0.67; p >

.19).

Table 12. Cell Means and Standard Errors (in Parentheses) of the percentage of correctly memorized items during Task Performance (Experiment 3).

enjoy-rule

Negative mood Positive mood

Total 7.62 8.00

(0.42) (0.44)

Errors 2.77 1.85

(0.61) (0.52)

Net performance index 4.85 6.15

(0.71) (0.67)

Note: Net performance index = detected symbols minus errors

4.3.3. Discussion

As expected and already demonstrated in Experiments 1 and 2, mood had again no effect on cardiovascular activity during the mood inductions, which were efficient according to the significant verbal mood manipulation check. Most relevant, instructing participants to use an “enjoy-rule” for resource mobilization during task performance led again to stronger SBP reactivity in a positive mood than in a negative mood. Given that this effect occurred this time in a memory task, it is evidently not limited to mental concentration, which is more connected to attention than memory.

Dans le document Mood and mental effort : informational mood impact on cardiovascular reactivity and the context-dependency of moods (Page 129-134)