Effect of Variation in Perceived Risk on the Secretion ...

Effect of Variation in Perceived Risk on the Secretion of β-Endorphin ROBERT A. JONES GARY D. ELLIS Department of Recreation and Leisure University of Utah Salt Lake City, Utah, USA It is currently unknown why individuals opt to participate in risk taking as a form of recreation. This study was designed to test the hypothesis that $-endorphin, a naturally produced opiatelike peptide, is secreted in response to a perception of risk, thereby reinforcing risk-taking behaviors. A 2 x 2 factorial design (Time x Perceived Risk) with repeated measures across both factors was used. The two levels of time were preand postexposure to a particular level of perceived risk. The two levels of perceived risk were high and low. Perceived risk was operationalized through the use of ropes course events of similar design but differing in exposure to height. The dependent variable was level of plasma β-endorphin. Exploratory analyses of subjective arousal, pleasure, and desire to repeat were also undertaken. Results indicated that plasma β-endorphin and arousal were significantly increased in the high perceived-risk condition. A Time X Risk interaction was identified for subjective pleasure. Although the means were in the hypothesized direction, no significant difference was found between low- and high-risk conditions for desire to repeat the experience. Keywords β-endorphin, risk, recreation

Why do individuals take risks as a form of recreation? Despite the availability of numerous recreation activities that entail little potential for substantial physical harm, thousands of persons opt to engage in activities such as Whitewater kayaking, rock climbing, and sport parachuting. Several attempts have been made to explain why individuals choose to participate in activities of this genre (Ewert, 1985; Ewert & Hollenhorst, 1989; Priest, 1992). However, these attempts have lacked an explicit conceptual and theoretical foundation and have therefore been descriptive rather than explanatory. The factors forming the substrate for risk taking as a form of recreation remain elusive. One basic explanation for engaging in these activities is that participants derive pleasure from their participation. Pleasure is a central element of recreation, play, and leisure. Recreation and pleasure cannot be dissociated unless one uses a behavioral classification system based solely on observable elements of the activity. If pleasure is to be understood, physiological response methods may prove to be useful because pleasure has a neurophysiological basis (Buck, 1988; Carlson, 1986; Smith, 1985). The neuromoduReceived 23 February 1995; accepted 8 February 1996. The basis for this article is Robert A. Jones's dissertation. This investigation was supported by Public Health Services Research Grant MO1-RR00064 from the National Center for Research Resources. Special thanks must be extended to Steve Bell and John Cederqist for their outstanding contributions to this study. Address correspondence to Robert A. Jones, 1953 East Calle de Arcos, Tempe, AZ 85284, USA. 277 Leisure Sciences, 18:277-291, 1996 Copyright © 1996 Taylor & Francis 0149-0400/96 $12.00 + .00

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R. A. Jones and G. D. Ellis

lator perhaps most often associated with pleasure is (3-endorphin, an extremely potent endogenous opiatelike peptide. (3-endorphin has been found to be secreted from the pituitary gland in response to psychological and physical stress (Oltras, Mora, & Vives, 1987). Stresses of this genre are one aspect of perceived-risk recreation activities. The possibility that p-endorphin secretion may serve as a positive reinforcement for engaging in perceived-risk recreation activities has not been explored empirically; therefore, the purpose of this study was to determine if (3-endorphin is secreted in response to engaging in an activity that features a perception of risk. We tested two primary hypotheses. The first hypothesis was that a significant interaction exists between perceived risk and time such that (3-endorphin levels would be highest in a postevent high-risk condition. The second hypothesis was that a preevent high-risk mean would be significantly higher than pre- and postevent low-risk means. These hypotheses indicate a main effect for risk and an interaction between risk and time. We also conducted exploratory analyses of subjective measures of arousal, pleasure, and desire to repeat the experience. We hypothesized that the respective means for arousal, pleasure, and desire to repeat the experience would be significantly higher under the high perceived-risk condition than under the low perceived-risk condition. We present a conceptual foundation for these hypotheses in the following section, along with a proposed neurotransmitter model of high perceived-risk recreation experiences.

Review of Literature Risk Risk is not a term that is exclusive to recreation venues. The literatures of the insurance industry and manufacturing abound with articles on the analysis and minimization of risk. Pertinent definitions of risk common in these literatures revolve around the concepts of probability of loss, magnitude of loss, and permutations of these two factors (Vlek & Stallen, 1981). These definitions address only objective, quantifiable risk as opposed to perceived risk. In addition, it should be noted that perceived risk has an emotional component that transcends cognition. Keyes (1985) addressed this point: "Real fear of possible loss is central to actual risk. Objective danger counts for less than perceived danger" (p. 25). For this study, we defined perceived risk as an emotional and cognitive response elicited by exposure to a perceived probability of loss of some magnitude. We operationalized risk in this study through the use of exposure to two levels of height, and we assumed that exposure to a greater height would increase the magnitude of potential loss, thereby increasing perceived risk. Perceived-Risk Recreation Perceived-risk recreation is a phrase coined in an effort to better represent the subjective reality of activities that include sports such as Whitewater kayaking and rock climbing. Meier (1978) and Schreyer, White, and McCool (1978) used the term risk recreation, and Miles (1978) preferred the phrase high adventure activities. As Keyes (1985) supported the primacy of subjective threat in the determination of risk and in recognizing that the injury-fatality rates associated with these activities are quite modest for adequately trained individuals (Outdoor Recreation Georgia Tech, 1988), the key to these activities must be the perceived risk in recreating.

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Biological Theories The theoretical basis for this study stems from the biological theories pertinent to risktaking behaviors and the prior research on p-endorphin. The biological theories of recreation revolve around the concept of arousal (Ellis, 1973; Iso-Ahola, 1980). In evaluating these theories, it must be recognized that the term arousal is being used to specify one dimension of a multidimensional construct. Buck (1988) and Carlson (1986) provided an excellent overview of the multidimensional nature of the nervous system and the effects of arousal within each system. For this study, it was sufficient to specify that arousal refers to the activation of the central and sympathetic nervous systems. An organism functioning in a state of optimal central and sympathetic nervous system arousal would be highly attuned to the surrounding environmental stimuli and physiologically prepared to fight, flee, or frolic. Hebb and Thompson (1954) proposed that organisms have an optimal level of arousal that they attempt to maintain. This optimal level is determined by the organism-environment interaction as well as the individual experience; thus, the process was considered to be dynamic. Berlyne (1960) refined the concept of optimal arousal by identifying three factors that influence organisms' arousal levels: novelty, uncertainty (dissonance), and complexity. Thus, a novel and complex activity with a lack of certainty regarding outcome (a common set of circumstances in perceived-risk recreation) would be arousing to an individual. Berlyne (1960) used the term arousal jag to refer to situations akin to some maximally challenging activities found within perceived-risk recreation. An arousal jag is a type of encounter in which the organism seeks a temporary elevation in arousal (achieving supraoptimal arousal) for the sake of the pleasurable relief associated with the anticipated reversal of that elevation. An arousal boost (Berlyne, 1971) is similar to an arousal jag, but less extreme. In an arousal boost encounter, the organism pursues a moderate increase in arousal due to the innate satisfaction of that elevation in arousal without concern regarding reversing the trend. It should be noted that arousal boost and jag behaviors are departures from the maintenance of an optimal state of arousal and describe behaviors that provide innate pleasure to the organism during the course of shifting the level of arousal. The arousal jag scenario is consistent with the assertion of Ellis (1973) that interactions with the environment that include novel, complex, or dissonant characteristics and move an individual toward an optimal level of arousal are accompanied by positive affect or pleasure. The pioneering work of Zuckerman (Zuckerman, Kolin, Price, & Zoob, 1964; Zuckerman, 1971, 1979) in sensation seeking has provided substantial insight into risk-taking behaviors. This body of work began as an attempt to predict reactions to sensory deprivation experiments and has evolved into a theory of sensation seeking as a trait with genetic, sociobiological, and biological bases. Sensation seeking is defined as "a trait defined by the need for varied, novel, and complex sensations and experiences and the willingness to take physical and social risks for the sake of such experiences" (Zuckerman, 1979, p. 10). Zuckerman (1979, 1983) developed a biological theory of sensation seeking that includes a variety of factors including assorted neurotransmitters, hormones, monoamine oxidase, and differences in how individuals react to external stimuli. This work stands as perhaps the most comprehensive biological model for the determinants of a sensationseeking trait. Further research by Johansson, Almay, von Knorring, Terenius, and Anstrom (1979) found that individuals who scored high on the Sensation Seeking Scale (high

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sensation seekers) had significantly lower basal levels of p-endorphin in their cerebrospinal fluid than individuals who scored low on this scale. If one assumes that involvement in risk-taking behaviors increases the secretion of (3-endorphin, this finding suggests that engaging in these activities may be a compensatory action to raise abnormally low baseline P-endorphin levels. This compensatory action fits well with the arousal boost and arousal jag phenomena described by Berlyne (1960, 1971). Although Zuckerman's work (1964, 1971, 1979, 1983) in sensation seeking addresses risk-taking behaviors and is psychophysiological in nature, this body of work is oriented toward the examination of a trait and isolating the determinants of that trait. The current study was directed at understanding risk as a transient state of the participant rather than as a trait or disposition. This factor, along with the reported psychometric difficulties with the Sensation Seeking Scale (Mehrabian & Russell, 1974; Ridgeway & Russell, 1980; Straub, 1982; Washington, 1990; Zuckerman, 1979), precluded the use of this literature as a theoretical basis for this study, although a great deal of overlap exists.

$-Endorphin Overview: (3-endorphin is one of a number of endogenous opiatelike peptides (OLPs). Classes of these OLPs include the enkephalins, the endorphins, and dynorphin. The OLPs within these classes appear to serve a wide variety of functions at a number of locations throughout the body. We focused on (3-endorphin because of its theoretical link to the experience of pleasure as well as the location of its receptor sites, its relative potency, and the factors that elicit secretion of this peptide. Locations of secretion and receptors: Pert and Snyder (1973) identified receptors for (3-endorphin in the limbic system and the medial thalamus. As demonstrated by Olds and Milner (1954), the limbic system is the brain's pleasure center. In addition, the limbic system serves to regulate sexual and emotional aspects of behavior as well as processing of memory (Diamond, Scheibel, & Elson, 1985). The thalamus is the gateway between the senses and the mind. The pathways for all senses except smell (olfaction) pass through the thalamus on the way to the cerebral hemispheres (Diamond, Scheibel, & Elson, 1985). Much as a key and a lock allow control over the functioning of a door, the positioning of the receptors for p-endorphin allow this OLP to influence vital and widespread aspects of behavior. The anterior lobe of the pituitary gland (adenohypophysis) has been noted as the major source of P-endorphin production in humans (O'Riordan, Malan, & Gould, 1988; Rose, 1985). However, p-endorphin must also be produced within the brain as significant levels are present in cerebrospinal fluid after hypophysectomy (surgical removal of the pituitary)(Rose, 1985). Indeed, very high levels of p-endorphin have been found in the hypothalamus, and moderate levels have been isolated in the mesencephalon (Reichlin, 1985). The mesencephalon includes the reticular formation, which plays a role in arousal, attention, movement, and vital reflexes; the periaqueductal gray matter, which controls sequences of movements that constitute species-typical behaviors as well as regulating sensitivity to pain; and the ventral tegmental area, which has been implicated with learning and schizophrenia (Carlson, 1986). Factors eliciting secretion: Guillemin et al. (1977) determined that P-endorphin and ACTH, a biochemical that provides for metabolic responses to stress, are secreted con-


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comitantly in response to pain. OLPs have also been found to be costored and coreleased with adrenalin (Evans, Erdalyi, & Barchas, 1986). Other factors, less severe than surgical stress or pain, have also been shown to elicit secretion of p-endorphin. Physical stress, such as exercise, has been shown to increase the secretion of P-endorphin significantly (Metzger & Stein, 1984; Morley, Benton, & Solomon, 1991). A diurnal cycle of p-endorphin secretion has also been identified (Stewart, 1985) that peaks in the early morning hours and declines throughout the course of the day. Fear as expressed by phobic anxiety has also been shown to increase p-endorphin levels (Thyer & Matthews, 1986), and rat pups have been found to secrete endogenous opiates on maternal separation, with even higher levels being found if they are separated from their littermates as well (Kehoe, 1988). In a pivotal piece of work, Oltras et al. (1987) found a significant increase (p < .01) in p-endorphin levels in nine elite runners in anticipation of a 22,000-meter officially sanctioned race. Blood samples were drawn as a baseline immediately before a regular training session several days before the race, before the warming-up period (20 min before the beginning of the race), and shortly after completion of the race. All samples were drawn between 8:40 P.M. and 10:40 P.M. in order to control for the diurnal variation in plasma p-endorphin levels (Stewart, 1985). A significant increase (p < .01) in plasma p-endorphin was found in the samples drawn immediately before the race when compared with the baseline samples. Samples drawn after the race contained a significantly higher level (p < .05) of P-endorphin than the prerace samples. This study is crucial to the relationship of P-endorphin to the perceived-risk recreation experience in that it indicates an anticipatory response to physical stress triggered by a psychological mechanism. In another study that related p-endorphin release to psychological stress, students exposed to emotional stress immediately before examinations were found to have elevated p-endorphin levels, and this elevation was found to be correlated with the extent of the emotional reaction to that stress situation (Breidenbach, Konig, Davies-Osterkamp, Luckhardt, & Nowacki, 1979). In fact, the activation of the hypothalamic-pituitary-adrenal axis has been viewed as the classical response to stress. This response leads to the release of corticotropin-releasing factor, causing the pituitary to secrete both ACTH and p-endorphin (Morley et al., 1991). This stance has received support with the finding that both intravenous and intracerebroventricular corticotropin-releasing factor injection will cause ACTH and p-endorphin to be released from the anterior pituitary (Ritchie & Nemeroff, 1991). Other findings suggest that psychological factors may play a role in mediating this response. Rose (1985) stated, "The influence of the endogenous opiates may be greater when cognitive appraisal modifies the intensity of the stressful stimuli" (p. 664). This suggestion fits well with the anatomical data that indicate direct or indirect innervation of the hypothalamus, which controls secretions from the pituitary via blood flow in the portal veins, from virtually all areas of the brain (O'Riordan et al., 1988). It becomes apparent that higher brain centers may elicit P-endorphin secretion in response to cognitive appraisal of exogenous stimuli and p-endorphin may also be secreted as part of the normal endocrine response to endogenous stimuli that may not be subject to such cognitive appraisal (i.e., a "hardwired" response). Behavioral effects: As with other opiates, the behavioral effects of p-endorphin are dependent on the dose. Low levels of secretion of p-endorphin have been found to increase locomotor activity (Mansour, Khachaturian, Lewis, Akil, & Watson, 1988; Szekely, 1983), ameliorate respiratory depression (Mansour et al., 1988), and decrease anxiety and

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provide for a markedly ebullient mood. Characterizations of mood under the influence of p-endorphin range from ''feelings of pleasantness" to "euphoria" (Bird & Kuhar, 1977; Rosenfeld, 1985; Schull, Kaplan, & O'Brien, 1981; Szekely, 1983; Wildmann, Kruger, Schmole, Neimann, & Matthaie, 1986). Higher doses of (i-endorphin have been shown to provide profound analgesia for painful stimuli (McGivern, Lobaugh, & Collier, 1981; Szekely, 1983), as well as more generalized depressive effects (Szekely, 1983). These effects are in keeping with two other classically recognized trademarks of opiates, tolerance and dependence. Pert (1976) determined that chronic administration of two types of OLPs, enkephalins and (i-endorphin, would elicit both tolerance to and dependence on the neurochemical.

Other Rewarding Neurotransmitters Although we delimited this study to exploring the possible role of p-endorphin in the perceived-risk recreation experience, we should note that electrical stimulation of a number of structures of the brain has been found to be reinforcing (Carlson, 1986). This suggests that more than one neurotransmitter system is involved in reinforcement. Of particular interest are dopamine, norepinephrine, and epinephrine. Dopamine is a catecholaminergic neurotransmitter and the immediate neurochemical precursor of norepinephrine. Cocaine is a widely recognized substance that functions as a dopamine agonist (a substance that either increases secretion or prevents reuptake, thereby making more of the biochemical available). Koob (1992) determined that the acute reinforcing effects of cocaine are dependent on the release of dopamine. It is interesting to note that dopaminergic and opiate reinforcement are somewhat interrelated. The reinforcing actions of opiates are dopamine-independent in the nucleus accumbens but dopamine-dependent in the ventral tegmental area (Koob, 1992). In a supporting study, Stinus, Cador, and LeMoal (1992) determined that chronic dopamine blockade reduced by 800% the amount of systemically administered heroin required to act as a reinforcing stimulus in place-preference experiments. However, this opiate supersensitivity was found to be specific to the nucleus accumbens as behavioral effects of opiate infusion to the ventral tegmental area were completely abolished by dopamine blockade. In addition to dopamine's role in reinforcement, it has also been suggested that dopamine is involved in the control of movement (Carlson, 1986) and in the initiation of responses to stimuli (Buck, 1988; Panksepp, 1986). Norepinephrine is the major neurotransmitter of the sympathetic nervous system and the immediate neurochemical predecessor of epinephrine. In addition to its role as a neurotransmitter, norepinephrine is secreted into the bloodstream by the adrenal medulla (Buck, 1988). Panksepp (1986) maintained that norepinephrine serves to increase the organism's sensitivity to relevant stimuli. Also, the sympathetic nervous system is partially responsible for an aroused affective state. The major role of epinephrine is as a hormone secreted from the adrenal medulla that provides for an increase in heart rate, the constricting of peripheral blood vessels, and an increased rate of metabolism (Carlson, 1986). It is interesting to note that the subjective experiences associated with epinephrine and norepinephrine are markedly different. Schildkraut and Kety (1967) concluded that secretion of norepinephrine is related to anger and aggression as compared with epinephrine secretion, which is related to anxiety and fear.


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Neurotransmitter Model of Perceived-Risk Recreation As a heuristic device, a model for high perceived-risk recreation experiences has been generated (Figure 1). The model addresses four levels of a singular experience along a timeline beginning with a perception of risk and ending with the conclusion of that singular event. The levels of the experience addressed are as follows: (a) the observable aspects of the engagement, (b) the cognitive aspects of the experience within the framework of attribution literature, (c) the subjective experience, and (d) the predominant neurotransmitter(s) relative to the subjective experience. Although we have not addressed the attribution literature to this point, the cognitive aspects of the perceived-risk recreation experiences could not be excluded from this heuristic device. Attribution theory addresses the perception of causative factors relative to events in the lives of individuals. Although attribution theory has been used extensively, it is important to note that it is a general approach that does not feature a singular theory (Morris, 1992). Weiner (1979) asserted that causal attributions occur along the continuous dimensions of internality, stability, and globality. The internality dimension varies from causative factors internal to the individual to those external to the individual. The stability dimension refers to relative permanence over time and varies from stable to unstable. The globality dimension varies from global to specific and addresses causation relative to the number of events (a singular event vs. all events). The neurotransmitters associated with each stage of the experience were chosen on the basis of the studies previously cited. In this study, we attempted to verify the opiate aspect of the model by testing hypotheses addressing increased p-endorphin secretion during perceived-risk activity involvement.

Observable

Cognition

Subjective Experience

Exposure to - Perceived— Risk Recreation Risk Opportunity Evaluation-

Arousal

I

r

Avoid-

• Engage-

Total Failure —tContinuum Total Success-

Predominant Neurotransmitter -Dopamine

—Arousal-

-Dopamine/ Norepinephrine

-Attention Diverted To Next Task

-Relaxation/ Low Dominance

-Return to Homeostasis

-AttentionFocused

-Arousal-

-Norepinephrine/ Dopamine

-Internal/ Stable/Global Attribution I External/ Unstable/Specific Attribution

-Fear/ Frustration

-Epinephrine/ Norepinephrine

t -Frustration/ Low Dominance 1

-Norepinephrine I

-Pleasure,ArousalLow Dominance

-fi-endorphin/ Norepinephrine

t —Internal/ Stable/Global Attribution

Desire To Repeat

Figure 1. Neurotransmitter model of a high perceived-risk recreation experience.

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Hypotheses For the individual in a stressful situation, such as a perceived-risk recreation experience, a low-dose release of P-endorphin would result in optimizing that individual in regard to coping with the perceived risk. The individual would experience less anxiety, tend toward a positive mood state, breathe more deeply, and be more active than normal. This would be an adaptive state for an individual under stress. Research by Oltras et al. (1987) indicated that this p-endorphin release response could occur in anticipation of an actual risk. In essence, the individual is rewarded by p-endorphin release for approximating the risk. It is likely that the stresses so integral to perceived-risk recreation would elicit secretion of p-endorphin. Further, it is likely that the reinforcing properties long associated with opiates provide for a positive association between exposing oneself to risk and some form of positive mood state and generally optimized physical functioning. It therefore seemed reasonable to test the hypothesis that P-endorphin will be secreted in response to engaging in an activity that features a perception of risk. We formulated two hypotheses to test the proposed interaction between perceived risk and time: H^

p-endorphin levels will be higher in the postevent, high-risk condition than in the other three treatment conditions.

H2:

p-endorphin levels will be higher before engaging in the high perceivedrisk treatment condition than before or after engaging in the low perceived-risk treatment condition.

We delimited the study to the issue of p-endorphin secretion under varying levels of perceived risk. This delimitation was established because of an anticipated insufficient sample size for adequate assessment of effects of risk and time on the subjective variables contained within the conceptualization of this study (arousal, pleasure, and desire to repeat the experience). However, it was appropriate to address these variables within the context of exploratory analyses. Hypotheses for these analyses are denoted ExHn. ExHj:

Arousal means will be significantly higher under the high perceivedrisk treatment condition than under the low perceived-risk treatment condition.

ExH2:

Pleasure means will be significantly higher under the high perceivedrisk treatment condition than under the low perceived-risk treatment condition.

ExH3:

Desire-to-repeat-the-experience means will be significantly higher under the high perceived-risk treatment condition than under the low perceived-risk treatment condition.

Method Research Participants We used statistical power analysis (Cohen, 1977) to determine the sample size needed for the experiment. On the basis of results of a study on p-endorphin levels of elite runners (Oltras et al. 1987), we used an effect size of .73 for the estimation. This effect size provided an F-test power of .93 for a sample of 9 and a power of .98 for a sample of 12.

Risk Variation and

fi-Endorphin

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This level of power was considered acceptable for the experiment; Cohen suggested .80 as a minimum level for statistical power. On the basis of these estimates, 14 students were recruited from undergraduate classes at a western university. Of these 14 volunteers, 12 completed the protocol. Nine were female and 3 were male. Ages ranged from 18 to 30 years, with the majority being in their early 20s. Recruitment involved visiting classes and providing a general statement of the study's purpose, an overview of the experimental manipulation, and information concerning the necessity of drawing blood on four occasions during the course of the experiment. Individuals with height or needle phobias were asked to not volunteer because phobic anxiety has been linked to release of p-endorphin (Thyer & Matthews, 1986). In addition, individuals with bleeding disorders or who were currently undergoing radiation therapy or chemotherapy were asked to not volunteer because of the risks to those individuals that are associated with repeated venipunctures. Design We used a 2 x 2 factorial design with repeated measures across both factors. The factors included time and perceived risk. The two levels of the time factor were pre- and postevent. The events involved two levels of perceived risk, high and low. These high and low perceived-risk treatment conditions were created through use of two ropes course events. Under the low perceived-risk condition, research participants were asked to walk 8.5 m along the top of a stable horizontal log that ranged in diameter from 18.5 cm to 16.5 cm. The distance from the top of the log to the ground was only 0.4 m. Under the high perceived-risk condition, research participants were asked to don a helmet, connect to a belay system, and walk 8.5 m on a horizontal log suspended 8.7 m above the ground. This "catwalk" log varied in diameter from 15.0 cm to 16.8 cm. To gain access to the catwalk, research participants climbed a 2.4-m ladder and then up a series of heavy-duty staples driven into one of the two vertical logs that supported the catwalk log. On conclusion of the traverse across the catwalk, research participants were lowered slowly to the ground by means of the belay system. The order of the two risk events was counterbalanced. Measurement $-endorphin: We assessed plasma p-endorphin levels through analysis of blood samples. Blood draws were performed after the research participants were shown the event and had been presented a description of the procedure, but before participation (preevent) and immediately after participation (postevent). The venipunctures were performed by registered nurses from the Clinical Research Center of the sponsoring university. The blood samples were collected in 3-ml EDTA tubes and were immediately placed in crushed ice. To enable the sample to be assayed in duplicate, 400 (il of blood were drawn at each of the four sampling sessions. After each session, the samples were removed from the ice and centrifuged at 2,000 rpm for 10 min. The samples were then placed in a medical sample freezer and kept frozen at -40° C until the blood assay was performed. The samples were analyzed by means of the Nichols Institute Diagnostics Allegro p-endorphin test kit. This is a double-antibody immunoradiometric assay that is designed specifically for determining the level of p-endorphin present in serum or plasma samples.

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The assay functions by binding the P-endorphin to a plastic bead that is coated by a solid-phase antibody during a 24-hr incubation period. The p-endorphin bound to the bead is exposed to a radioisotope-labeled antibody that completes the solid-phase antibody- and p-endorphin-labeled antibody "sandwich" coating the outside of the bead. All unbound materials are then rinsed away, and the level of bound radioactivity is measured with a gamma counter. The concentration of the P-endorphin in the sample is directly proportional to the level of radioactivity that is present. One source of measurement error in assays of this type is cross-reactivity. In a cross-reactivity situation, substances other than those of interest bind to the antibodycoated bead and are erroneously identified as the target substance. The Nichols Institute reported a total of 16.1% cross-reactivity of P-endorphin with other substances, the most notable of which is p-lipotropin. The measurement of p-endorphin in this study, therefore, can be considered to be approximately 83.9% accurate. The intra-assay variance was 2.7%, which was somewhat lower than the coefficient of 4.1% reported by the manufacturer of the assay. Because the assay kits were manufactured in the same lot and all assays were performed on the same day, we considered it unnecessary to evaluate interassay variance. Arousal and pleasure: Arousal and pleasure were measured through use of adjectives from Mehrabian and Russell's (1974) Semantic Differential Measures of Emotions scale. That scale uses 18 bipolar adjectives to quantify pleasure, arousal, and dominance. The dominance dimension was not considered relevant to the conceptual foundation of this study, so we do not discuss results based on that variable here. Examples of adjectives from the arousal dimension are unaroused-aroused, stimulated-relaxed, and wide awakesleepy. Examples of adjectives from the pleasure dimension are happy-unhappy, annoyed-pleased, and satisfied-unsatisfied. For this study, the bipolar adjectives served as anchor points on a 100-mm line, with incremental numbers marking each 10-unit interval (10, 20, 30, etc.). We asked research participants to mark a point on each line to indicate their "feelings right now." Desire to repeat: One assumption implied by the conceptualization of the study was that heightened p-endorphin levels would be associated with greater desire to repeat the activity. We quantified desire to repeat, therefore, by asking research participants to indicate, along a 100-mm line, the likelihood that they would choose to repeat the event if given the opportunity (0 = very unlikely, 100 = very likely). Manipulation check: As a manipulation check of the perceived-risk variable, we asked research participants to rate their perceived risk on a 100-mm line ranging from 0 (no risk) to 100 (extreme risk). These assessments were taken before engagement in each event and after each event. Procedure Data were collected on three consecutive Thursdays in July, providing a minimum of 1 week between experimental sessions. Blood samples were collected between the hours of 5:00 P.M. and 7:00 P.M. on each of the dates in order to control for the diurnal cycle of p-endorphin secretion (Stewart, 1985). To avoid contamination through exposure to other research participants, all testing was conducted individually. Preevent measures were taken after the research participants had been shown the


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Table 1 Treatment condition means and standard deviations Marginal means Variable

Preevent Postevent

P-

35.93 9.43 346.71, 54.54 438.88 53.57 — —

endorphin Arousal Pleasure Desire to Repeat

36.80 9.01 413.71, 77.94 462.46 61.12 — —

High risk

Cell means Low risk

Prelow

Postlow

Prehigh

Posthigh

40.05. 32.70, 32.58 32.83 39.31 40.78 12.50 8.04 16.82 5.89 4.06 12.11 476.04c 284.38C 245.38 323.17 447.83 504.25 61.61 85.21 74.94 106.04 75.84 77.00 452.88 448.88 454.50 442.42^ 423.25^ 482.50, e 55.27 59.11 56.51 78.57 67.86 53.84 — — — — 62.17 71.00 — — 35.17 39.81 — —

Note. Means with the same subscript are significantly different at p < .05.

event and provided a description of the task to be accomplished for each event. Postevent measures were taken within 3 min of research participants' completion of the event. For reasons of sanitation, both pre- and postevent measures were taken in a room that was approximately a 90-s walk from the event setting. The absence of a closer room was of some concern to us because the lag time between exposure to the event and the subsequent venipuncture allowed additional time for p-endorphin to bind to receptor sites, thereby decreasing the amount of p-endorphin captured in the sample. Data Analyses We calculated arousal, pleasure, and P-endorphin means and standard deviations for each treatment condition. Hypothesis tests were conducted by means of repeated measures analysis of variance procedures. Significant interaction effects were followed up with t tests to examine differences between cell means.

Results Manipulation check The manipulation check supported the effectiveness of the operationalization of perceived risk. The mean perceived-risk score for the low-risk event condition was 2.84 and that for the high-risk event was 55.92, F(l,44) = 149.03, p < .001. These results clearly showed that research participants evaluated the high-risk event as being substantially greater in perceived risk than the low-risk event. Tests of Hypotheses Results of hypotheses tests are summarized in Table 1. That table includes marginal means representing the main effects as well as cell means, on which interaction effects are based. We found a risk main effect in the analysis of p-endorphin. The high-risk event mean was 40.05 pg/ml, and the low-risk event mean was 32.70 pg/ml. The difference between these two means was found to be significant, F(l,44) = 5.16, p = .04. Thus, P-endorphin varied

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as a function of perceived risk, without respect to actual behavioral engagement in the activity. Table 1 also summarizes results of the analyses involving arousal, pleasure, and desire to repeat. In the analysis of arousal, main effects were identified for both risk, F(l,44) = 72.05,p < .001, and time, F(l,44) = 25.61,/? < .001. Examination of the pattern of means revealed that arousal scores were higher postevent than preevent (413.71 vs. 346.71) and that arousal scores were higher in the high-risk condition than in the low-risk condition (476.04 vs. 284.38). We found a significant Time x Treatment interaction effect in the analysis of variance of the pleasure variable, F(l,44) = 22.99, p < .001. Follow-up tests between cell means revealed significant differences between post-high and pre-high event means (482.50 vs. 423.25, respectively); £(11) = 3.89, p - .003, and between post-high and post-low event means (482.50 vs. 442.42, respectively, t{\\) = 2.45, p = .032. In the analysis of the desire-to-repeat variable, we found the means to be consistent with the hypothesis that desire to repeat would be stronger in the post-high condition than in the post-low condition. The post-high mean was 71.00, and the post-low mean was 62.17. This difference was, however, found to not be significant, t(ll) = .59, p = .566.

Discussion (3-endorphin was found to be secreted in significantly (p = .04) higher amounts as a result of exposure to an activity featuring a perception of risk. We should note that this difference was identified despite the time lag between the treatments and the blood sampling sessions, thereby decreasing the amount of unbound (3-endorphin that could be captured in the samples. This increased secretion of an endogenous opiate may serve as a powerful incentive to engage in risk-taking behaviors. As the previously identified motivations for participating in perceived-risk recreation activities have been psychological in nature, the identification of a psychophysiological substrate for participation opens the door for new insights into activities of this genre. This is important as failure to address motives from sources other than the psychosocial will limit and bias understanding of why individuals act as they do. The hypothesized interaction between risk and time relative to (3-endorphin levels was not supported. The previously mentioned time lag between treatments and sampling sessions may have masked such an interaction if it exists. A second possible explanation for failure to support this hypothesis is a conceptualization versus operationalization limitation with perceived risk. Participants were asked how risky they thought walking down the log would be preevent and was postevent. The tendency would be for participants to provide a similar rating rather than cope with cognitive dissonance resulting from a shifting appraisal. If this is the cause for failure to support the interaction hypothesis, it demonstrates how the subtleties of wording in questionnaires can influence outcomes. A secondary purpose of this study was to test the conceptualization of factors ostensibly involved in a high perceived-risk experience. The factors involved in this study were arousal, pleasure, and desire to repeat the experience. The results support a role for both arousal and pleasure in experiences of this type. Although the hypothesis for desire to repeat the experience was not supported, this may have been due to the operationalization of high perceived risk (some participants found it to be a bit extreme). This hypothesis should be reexamined in a more sensitive manner. The findings of this study generally support the aspects of the model examined. The cognitive evaluation of the high-risk event did lead to an increase in the subjective

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experience of arousal. In addition, engagement in the high-risk event did result in increases in the subjective experiences of pleasure and arousal as well as the secretion of β-endorphin. The proposed increase in the desire to repeat the experience was not supported by the findings, but this may be due to the extremes of the manipulation of the perceived-risk variable, as has been previously discussed. This study and the associated model view reasons for participation from a perspective quite different from the more generally accepted psychosocial approach. However, examining the substrates of participation from only one approach is like trying to understand a tiger by looking only at its tail. If we are to ultimately understand why individuals take risks as a form of recreation, we must admit that there is no homunculus.

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