واکنش پذیری قلب و عروق در طول صحبت های عمومی به عنوان تابعی از متغیر های شخصیت

Abstract An experiment was conducted to assess the effects of a real-life stressor (public speaking) upon cardiovascular reactivity (CVR). Changes in blood pressure and heart rate from baseline to task were measured in a sample of 86 men and women. The purpose was to examine the effects of individual differences (Type A personality, hostility and gender) on CVR. Participants gave a 6-min oral presentation during which they were evaluated by their professor and with classmates as the audience. Results indicated that all participants had marked CVR during public speaking. There were differences in reactivity patterns between men and women, but personality did not play a role except for high hostile men. It is suggested that intense stressors may result in high levels of CVR independent of personality variables that moderate reactivity at lower levels of stress.

. Introduction Cardiovascular reactivity may be defined as a change in a relevant variable, such as blood pressure, from resting baseline to task conditions. Typically, the task involves mental effort, psychomotor skill, social evaluation or some other psychological or physical threat. There is evidence supporting the idea that the tendency to react strongly to psychological or physical challenge is a reliable individual trait, demonstrating test–retest reliability over a period of 10 years or more (Sherwood and Turner, 1992 and Sherwood et al., 1997). A body of literature has developed to indicate that the tendency to show cardiovascular reactivity is influenced by personality variables for Type A (Juszczak and Andreassi, 1987, Ganster et al., 1991 and Sundin et al., 1995) and hostile men (Brown and Smith, 1992 and Bongard et al., 1998). Not as much research has been devoted to personality factors as moderators of CVR in women, and the results have been largely negative. A review by Lawler et al. (1990) led to a conclusion that small sample sizes may have accounted for the mixed findings regarding personality and CVR for women. Lawler et al. (1989) did report greater CVR for Type A women when a real-life stressor was used (a midterm examination). Later, Fichera and Andreassi (1998) observed greater CVR for Type A and for hostile women in two tasks (an oral quiz and reaction time). The objective in the present investigation was to determine the CVR of both men and women to a task that is likely to be very stressful, a real-life classroom speech for which the student receives a grade. The personality variables selected for study were Type A/B behavior and hostility. It was expected that Type A men and women would demonstrate higher CVR in terms of blood pressure (systolic, diastolic and mean arterial pressure) and heart rate (HR) than Type Bs in this public speaking task. It was also predicted that women and men scoring high on a measure of hostility (Cook–Medley Hostility Scale) would demonstrate higher blood pressure and HR than those scoring low on the scale. Previous findings (Matthews and Stoney, 1988, Girdler et al., 1990 and Stoney, 1992) also suggest that men and women would differ in their reactivity profile, with men showing higher reactivity on all variables except heart rate.

Results This study had between subject factors in order to allow comparisons between Type A and Type B participants and high and low hostile individuals. A within-subject comparison was used to compute the degree of CVR, or changes in measures from baseline to task. Mean baseline physiological measures were computed for HR, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) for Type A and B and men and women (see Table 1). None of the baseline differences between Type As and Bs were significant. Differences in baselines between men (men higher) were significant for MAP, t=4.98, d.f.=64, P<0.001; SBP t=6.59, d.f.=64, P<0.001; and DBP, t=3.32, d.f.=64, P<0.01. These tests were two-tailed and were significant even after applying the Bonferroni correction for computing multiple t-ratios. Reactivity scores were computed by subtracting mean baseline measures from the mean level of a particular measure during the speech. So, for example, a mean HR reactivity of 29.71 for women indicates that, on the average, women’s HR increased by almost 30 b.p.m. during the speech as compared to the baseline measurement (see Table 2). Examination of Table 2 reveals that reactivity on all measures was very high. The BP units are in millimeters of mercury (mm/Hg). Table 1. Cardiovascular measures during baseline for Type A and B and for men and womena Baseline Type A Type B Men Women (N=27) (N=20) (N=30) (N=56) MAP 92.4 96.5 99.9 90.3 Heart rate 83.7 83.8 77.8 83.2 Systolic BP 122.7 126.8 132.4 117.8 Diastolic BP 70.7 75.6 77.4 70.4 a Notes. MAP, mean arterial pressure; BP, blood pressure. Blood pressure is expressed in mmHg. Table options Table 2. Mean reactivity and differences between men (N=30) and women (N=56) and univariate analysis of variance a Mean reactivity Univariate ANOVA Men Women d.f. F P MAP 22.22 19.51 (1, 84) 6.17 0.015* Heart rate 23.94 29.71 (1, 84) 5.54 0.021* Systolic BP 25.87 24.08 (1, 84) 2.31 0.132 Diastolic BP 19.36 16.14 (1, 84) 9.49 0.003** a Notes. Mean reactivity is the difference between baseline and task levels. MAP, mean arterial pressure; BP, blood pressure. Significance tests are two-tailed. * Significance at the 0.05 level. ** Significance at the 0.01 level. Table options A multivariate analysis of variance (MANOVA) was performed to determine if the reactivity scores differed significantly from zero. A resulting equivalent of Hotellings T square, F=17.2, d.f.=4,81, P<0.001, indicated significance. Table 2 also shows the results for a univariate analysis of variance (ANOVA) computed for the male–female differences. The males showed significantly higher BP reactivity (F=9.49, d.f.=1,84, P<0.003 and F=6.17, d.f.=1,84, P<0.015, respectively, for DBP and MAP), whereas the women had greater HR reactivity (F=5.54, d.f.=1,84, P<0.021). It was expected that Type A and high hostility would be predictive of greater reactivity. Correlations were run in order to analyze the relationships between personality and changes in HR and BP. None of the personality measures were significantly correlated with any of the reactivity scores. Mean reactivity scores were computed for Type A, Type B and mid-range scoring participants. A MANOVA was computed for the three groups to determine whether Type A’s mean reactivity scores differed from the other groups. A Wilk’s Lambda, F=0.961, d.f.=4,81, P>0.05 indicated non-significance. All univariate tests were also insignificant. Differences in reactivity of those scoring high and low in hostility were analyzed to see if they reacted differently to the stressor. A MANOVA was performed resulting in A Wilk’s Lambda, F=0.574, d.f.=4/81, P>0.05, indicating non-significance. All univariate F statistics were also non-significant. Separate analyses for hostility and reactivity were conducted for men and women. The average hostility scores of the high and low hostile men were not different from the respective average hostility scores of the high and low hostile women. There were no differences in baseline cardiovascular measures between high (n=15) and low (n=15) hostile men and between high (n=28) and low (n=28) hostile women. For men scoring high in hostility, their MAP reactivity (mean=23.78) was greater than those scoring low (mean=19.42, F= 7.62, d.f.=1/22, P<0.01). The same pattern was observed for DBP. The high hostile men had a mean increase of 20.86 mmHg for DBP, whereas low hostiles had mean increases of 17.17 mmHg (F=3.49, d.f.=1/22, P<0.05). For women, there were no significant differences in reactivity between those scoring low and high on the hostility scale. There were several apparent physiological differences between men and women, independent of personality (see Fig. 1). A MANOVA was conducted to test for differences between the sexes. The differences between baseline and task levels for the four cardiovascular measures were entered as dependent variables. A Wilk’s Lambda, F=3.88, d.f.=4,81, P<0.006, indicated that the sexes differed in one or more of the reactivity indices. In particular, univariate F statistics showed that men and women differed in three out of the four reactivity indices, DBP, MAP and HR (see Table 2). Fig. 1 graphically illustrates CVR during the classroom speech. Note the greater HR reactivity for women and greater BP reactivity for men. Reactivity to class presentation for women (N=56) and men (N=30). MAP and BP are ... Fig. 1. Reactivity to class presentation for women (N=56) and men (N=30). MAP and BP are expressed in mmHg and heart rate in beats per minute (b.p.m.).