The Psychological Record, 2012, 62, 69–82
Experimenter Effects on Cardiovascular Reactivity and Task Performance During Mental Stress Testing Nicole Siegwarth, Kevin T. Larkin, and Christine Kemmner West Virginia University
Experimenter effects have long been hypothesized to influence participants’ responses to mental stress testing. To explore the influence of experimenter warmth on responses to two mental stress tasks (mental arithmetic, mirror tracing), 32 young women participated in a single 45-min experimental session. Participants were randomized into warm experimenter or cold experimenter conditions that were operationalized using differential contact scripts, interpersonal styles, and attire. Heart rate (HR) and systolic and diastolic blood pressure (SBP and DBP) were measured during rest and task periods, and participants completed subjective ratings of anxiety and several items rating the experimenter. Results showed greater effort and improved performance on both tasks for participants in the warm experimenter condition, although no significant differences in HR, SBP, DBP, or subjective ratings of anxiety were observed between the conditions. These findings suggest that experimenter effects have a more robust influence on motivational factors than on physiologic or emotional response parameters. Key words: experimenter effects, mental stress testing, cardiovascular reactivity, task performance A considerable amount of research in health psychology has employed methods of mental stress testing to examine whether the magnitude of an individual’s response to stress might explain how psychological constructs lead to subsequent medical complications (see Blascovich & Katkin, 1993; Manuck, Kasprowicz, Monroe, Larkin, & Kaplan, 1989; Turner, 1994). Although much has been learned using this experimental approach, lesser attention has been paid to exploring the nonspecific laboratory factors that might influence study outcomes. One important factor of this type is the nature of the interaction between the experimenter and the study participant. In some laboratories, experimenters wear laboratory coats and interact with participants in superficial and distant manners, and in other laboratories, interactions between experimenter and participant are more casual and experimenter attire less professional. It is possible that differences in these nonspecific components of the laboratory environment contribute to differential study results that often comprise this literature and thus are worthy of empirical scrutiny. The importance of considering experimenter effects on outcomes in experimental studies dates back to the work of Rosenthal (1966), who documented the influence of a Correspondence concerning this article should be addressed to Kevin T. Larkin, Department of Psychology, 53 Campus Drive, West Virginia University, Morgantown, WV 26506-6040. E-mail: Kevin.
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variety of experimenter characteristics (e.g., sex, ethnicity, attire, warmth) on study outcomes. Because mental stress testing involves interactions between experimenters who induce stress (e.g., through harassment or maximizing evaluative anxiety) and participants who engage in the stressful tasks, it is quite likely that the experimenter characteristics identified by Rosenthal decades ago continue to exert important effects on experimental outcomes. In fact, in an early study of the experimenter effect, Hicks (1970) measured physiological responses to mental stress in a sample of men. In this study, the experiment was conducted by a stoic, “robotic” male experimenter, a reserved, business-like female experimenter, or a friendly, social female experimenter. Results revealed clear experimenter effects not only on task performance but also on physiological measures. Accuracy in detecting taboo words was better and heart rate and skin conductance responses were lower when the session was conducted by the social female in comparison to the other two types of experimenters. Additional research in the area of experimenter effects has showed that (a) the extent to which an experimenter smiles and glances at study participants is positively correlated with scores on verbal learning tasks (Page, 1971); (b) the “seriousness” of the experimenter influences whether differential pupillary response magnitudes are observed while viewing slides of nude men and women (Chapman, Chapman, & Brelje, 1969); (c) the sex and personality characteristics of the experimenter influence rate of verbal learning (Binder, McConnell, & Sjoholm, 1957); (d) the sex and attractiveness of the experimenter influence ratings of success in response to photographs of various people (Barnes & Rosenthal, 1985); and (e) formal modes of interaction between participant and experimenter are associated with increased socially desirable responding to explicit sexual stimuli (Abramson, Goldberg, Mosher, Abramson, & Gottesdiener, 1975). Evidence for experimenter effects even exists in the animal literature in a study comparing behavioral performance to a shock-avoidance task of rats handled by technicians with hesitant versus confident handling skills (Elkins, 1987). Despite the general acknowledgment that experimenter effects strongly influence study results, the majority of experimental work employing mental stress testing in the past employed single investigators (McGuigan, 1963; Silverman, 1974; Suls & Gastorf, 1980), a state that has likely persisted to the present time. Additionally, except for some relatively recent work examining experimenter effects and the demonstration of paranormal activity (e.g., Watt & Wiseman, 2002; Watt & Ramakers, 2003) and a study showing that mood effects in response to exposure to pheromones were influenced by the sex of the experimenter (Lundström & Olsson, 2005), the current literature is devoid of studies examining experimenter effects. The majority of investigations examining cardiovascular reactivity to mental stress have been conducted in laboratory settings, where standardized stimulus presentations can be optimized. However, a considerable degree of variability exists across laboratories regarding participant recruitment and selection procedures, laboratory protocols, and the nature of the interaction between study participants and experimenters. Based upon our knowledge that characteristics of experimenters influence task performance (Binder et al., 1957; Hicks, 1970; Page, 1971) and, in some cases, physiological responses (Chapman et al., 1969; Hicks, 1970), it is important to examine these specific characteristics empirically. Through a better understanding of these experimenter effects, we will be able to make meaningful comparisons of results across studies that have employed different experimenters in differing laboratory contexts. In their review of experimenter characteristics that influenced outcomes of studies that employed physiological measures, Krantz and Ratliff-Crain (1989) suggested that both race and sex of the experimenter be reported and considered as important factors in making cross-study comparisons of findings. In particular, the matching of participants and experimenters on the basis of race and sex was an important consideration when making generalizations from one study to another. However, very little attention has been paid to more modifiable experimenter characteristics, like warmth and attire of the experimenter, among studies examining physiological reactions to mental stress.
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The purpose of the present study was to examine the relation between the experimenter– participant interaction and cardiovascular reactivity and task performance during two commonly used laboratory stressors: mental arithmetic and mirror tracing. Rather than focus on the more commonly studied experimenter characteristics of sex and ethnicity, we chose to examine attire and warmth, specific attributes of the experimenter identified by Rosenthal (1966) that are relatively understudied and infrequently reported. A warm experimenter condition and a cold experimenter condition were examined by manipulating the experimenters’ status, demeanor, dress, and evaluative emphasis during all interactions with participants. Two separate scripts were used (see the Appendix) during laboratory visits as well as during telephone calls with participants before the laboratory session. It was anticipated that a perceived positive interaction with a warm, less socially threatening researcher in the laboratory setting (i.e., the warm experimenter condition) would result in improved performance and attenuated physiological responding to stressors, and a perceived negative interaction with the experimenter during the study (i.e., the cold experimenter condition) would result in poorer performance and enhanced cardiovascular activation.
Method Participants One hundred undergraduate women enrolled in psychology courses were screened for participation in this study, which was approved by the Institutional Review Board for the Protection of Human Subjects at West Virginia University. Thirty-two unmarried women from the screening sample were selected to participate in the second phase of this study. Exclusion criteria included smokers, volunteers who were taking medications that affected the autonomic nervous system or cardiovascular functioning, and those with chronic medical or psychiatric conditions. Volunteers reporting irregular menstrual-cycle lengths or those having prior experience in participating in studies that employed mental stress tasks were also excluded. The 32 participants provided informed consent and were randomly assigned to cold experimenter and warm experimenter groups, with the groups balanced on family history of cardiovascular disease and current use of oral synthetic hormones, because both have been shown to affect cardiovascular reactions to stress (Jorgensen & Houston, 1981; Von Eiff, Plotz, Beck, & Czernik, 1971). As depicted in Table 1, the two experimental groups were comparable on all demographic variables, except for number of minutes of exercise per week. Women randomized to the warm experimenter condition engaged in more exercise weekly than those in the cold experimenter condition, F(1, 30) = 4.48, p
