Indivdual Differences In Pain Tolerance Psychology Essay

Indivdual Differences In Pain Tolerance Psychology EssayIt is gener tout ensembley agreed that the perception of perturb does not only depend on the noxious input, but similarly on a variety of psychological variables including an individuals mad state. The corpus amygdaloideum is one area of the brain linked with the regulation of two emotion and smart (Lapate, Lee, Salomons, van Reekum, Grieschar Davidson, 2012). This region has also been implicated in character onset and the act of cursing. The current occupy aimed to expand on previous work looking into the hypoalgesic install of swearing on aggravator (Stephens, Atkins and Kingston, 2009 Stephens Umland 2011) whilst also examining the office of trait onset and sex activity. Participants consisted of 50 students from the University of Central Lancashire. They took part in two heatless vasoconstrictor task trials whilst either cursing or repeating the volume chair. They also completed the Trait Aggression Quest ionnaire (Buss Perry, 1992). Physiological readings of heart browse and systolic/diastolic rake haul were downn along with common cold pressor latency. It was show that swearing had no impact on pain tolerance and there were no differences in physiologic reading amidst any of the marks. However, the results showed that both(prenominal) staminates and females who patsyd high-pitched on the trait antagonism questionnaire could harbor the cold pressor task for endless than those low in trait aggression. Males also lasted lengthy on the cold pressor task than females crossways both the swearing and non-swearing positions. The lack of findings with regards to swearing could be due to the manner in which participants were asked to curse. Despite this, the findings do go for the idea that individual differences affect to be taken into account when studying pain and when dealing with pain in the clinical population.Physical pain has been field of honor to vast amounts of research across various disciplines. From an evolutionary point of view, pain serves an important purpose. For example, it motivates action to escape or avoid noxious stimuli (Ploghaus, Tracey, Gati, Clare, Menon, Matthews, Nicholas Rawlins, 1999). The more(prenominal) that is discovered about the physiological and psychological processes involved in the perception of pain, the more complex it has become (Ogden, 2007). Traditionally, the main body of research into pain has been on the pharmacological control of pain and has been foc consumptiond on the spinal cord processes of pain relief. As more is be learnt about the different types of pain modality bodys it is nice clearer that pharmacology is not the only way to manipulate these mechanisms (Villemure Bushnell, 2002). More recent evidence has been provided using neuroimaging as a center to advertize explore these mechanisms. useful neuroimaging has shown that certain areas of the brain are activated when pain is exp erienced. These include the thalamus, somatosensory and prefrontal cortices and the anterior cingulate cortex (Ploghaus et al, 1999). However, recent research on pain has focussed more on the spot that emotions play in pain regulation. The current view is of pain is much more multidimensional. This means the perception of pain does not necessarily depend on the level of noxious input rather it is heavily influenced by many psychological variables (Wiech Tracey, 2009). The turned on(p) dimension of pain is further supported by findings that show a large percentage of neurons in the medial thalamus that respond to noxious stimuli applied directly to the skin are chatoyant depending on the motivational and affective state of the animal (Price, 2002 cited in Wickens, 2009). in that respectfore it is necessary to study other(a) areas of the brain in relation to pain.More and more research is showing that the amygdaloid nucleus may play an important role in the integration of affec tive regulation and pain perception (Lapate, Lee, Salomons, van Reekum, Grieschar Davidson, 2012). victimization a combination of behavioural, physiological and neuroimaging methods (Lapate et al. (2012) demonstrated that both pain and emotion regulation are reflected in amygdala function. Other recent studies have also focused on the influence emotions have on pain. For example, Godinho,Magnin,Frot,Perche Garcia-Larrea (2006) demonstrated that empathy with other peoples suffering increased a participants own reported pain intensity. In addition, De Wied and Verbaten (2001) conducted a study looking at the effect positive and prejudicial pictures would have on participants pain tolerance. They found that participants viewing the positive pictures prior to the task could withstand pain for eight-day than participants viewing the negative pictures before the task. With regards to negative emotions it has been found that inducing anger or sadness (Rainville, Bao Chrtien, 2005) or a depressed image (Berna, Leknes, Holmes, Edwards, Goodwin Tracey, 2010) in healthy participants increases pain intensity and leads to individuals rating pain as more unpleasant than if these negative emotions had not been induced. Given that emotions are linked to the make of pain, research has also explored the role they play in its regulation. For example recent research has looked at the effects of swearing on pain tolerance.The use of proscribed linguistic communication, or swearing, is a prominent yet understudied part of human language (Van Lancker Cummings, 1999) which is used across all cultures (Pinker, 2007). Swearing can be used as a means to express emotion, particularly negative. The primary meanings of offensive boys are connotative (Jay Janschewitz, 2008) rather than denotative meaning they have an emotional aspect distinct from the actual meaning of the word. As soon as a child learns to speak, they learn to curse. Children learn that cursing is a form of co ping with accent mark and it has been hypothesised that being punished for cursing as a child can lead to the words holding a negative emotional connotation for the substance abuser (Jay, King Duncan, 2006). Therefore it is important to explore how swear words effect emotions compared to normal language.It has been suggested that the connotations and denotations of words are actually processed and stored in different unwrap of the brain, with denotation being primarily dealt with in the neocortex of the left hemisphere and connotation being processed across connections betwixt the neocortex and the limbic system in the right hemisphere (Pinker, 2007). Interestingly it appears that the neuropathology of swearing is distinct from the main language areas of the brain. This can be capturen in cases of severely aphasic patients where cursing is make with almost perfect articulation in comparison to the patients disabilities in other areas of language and speech (Van Lancker Cummi ngs, 1999). It has also been found that for patients suffering from coprolalia (the obscene linguistic outbursts of Gilles de la Tourettes syndrome) the symptoms are the same (although culturally specific taboos) in different languages which is evidence to support the act of cursing as having a neurobiological basis (Pinker, 2007). The amygdala has also been implicated in swearing with neuroimaging studies showing increased activation in this area of the brain on hearing/saying taboo words (Jay, 2000). However, despite swearing being common in both clinical and non-clinical populations, it is a relatively neglected area of study. This may be due partly to a universal negative reaction to profanity (Van Lancker Cummings, 1999). In particular it is surprising that swearing as a repartee to pain has assembled such(prenominal) little attention in the scientific community.To date there appears to be only two studies in the area of swearing as a reception to pain, both of which were conducted by Dr Richard Stephens (Stephens, Atkins and Kingston, 2009Stephens, et al. 2009 Stephens Umland 2011).In the first-year of these studies Stephens et al. (2009) looked at swearing as a retort to pain by asking participants to submerge their hand in halt cold ice water (the cold pressor task). They hypothesised that swearing would be a maladaptive response to pain. In total 67 participants took part in a swearing and non-swearing trial. In the swearing trial they were asked to repeat a swear word they would use if in pain and in the non-swearing trial they were asked what word they could use for a table. Stephens took heart rate readings as well as using a perceived pain get over. In this study he found that swearing increased cold pressor latency (i.e. the time that they could keep their hand in the ice water), lowered pain perception and was accompanied by an increased heart rate. The increased heart rate is indicative of openhearted nervous system activation, or th e fight or flight response. As this study included both male and female participants the element of gender based differences in pain tolerance had to be considered. While this is a physical difference, the emotional effect of swearing for males compared to females could affect pain tolerance.The main gender difference with regard to pain tolerance found in Stephens et al.s (2009) study was that males could withstand the cold pressor task for longer than females. Women have been found to show greater sensitivity to experimentally induceds pain than men (Riley, Robinson, Wise, Myers Fillingim, 1998) although a review of studies conducted over the other(prenominal) ten years looking at pain and gender suggests that pain tolerance is the only measure in which there is momentous difference between males and females during the cold pressor task (Racinea, Tousignant-Laammec, Kloda, Dione, Dupuis Choinire, 2012). Other gender differences in the study by Stephens et al. (2009) were obser ved with females having a greater reduction in perceived pain and a greater increase in heart rate during the swearing condition. This could be due to gender differences in swearing. For example, it has been found that females perceive more index number in swear words than males (Dewaele, 2004). It has also been found that although swearing frequency is similar across both genders, males tend to be more offensive than females (Jay Janschewitz, 2008). There have also been inconsistent results in studies looking at physiological responses to pain in men and women. Maixner and Humphrey (1993) found that women responded to pain with an increased heart rate, as shown in Stephens et al. (2009), and men responded to pain with an increase in rail line squeeze. However a more recent study conducted by alAbsi, Peterson and Wittmers (2002) found a alliance between blood pressure and pain perception only amongst their female participants whilst other studies have found no evidence of gende r differences when looking at the blood pressure/pain relationship (Helfer McCubbin, 2001 Poudevigne, OConner Pasley, 2002). These gender differences could go some way to explain why swearing has the different effects on pain perception and physiological responses.In a second study conducted by Stephens Umland (2011) doubled earlier findings in a second study on 71 participants. , most of the results from the first study were replicated. Participants were able to keep their hand in the cold water for longer if they were swearing, and heart rate was also increased. With regards toHowever, when they looked at gender differences they found males lasted longer during the cold pressor task than females as before but this time there was no dramatic change in heart rate for the female participants.One possible reason for swearing being an effective response to pain is that it could activate part of the brain known as the Rage Circuit. This is an evolutionary response in mammals which g oes from part of the amygdala, through the hypothalamus then into the midbrain. It is like a sudden reflex response to pain or frustration. When this happens the rage circuit triggers the move of the brain connected with negative emotion including words with a strong emotional connotation such as swearing (Pinker, 2007). Indeed, Stephens et al. (2009) suggested that swearing may be effective due to it inducing a negative emotion despite previous research suggesting that negative emotion actually decreases pain tolerance and increases pain perception (Berna et al., 2010 De Wied Verbaten, 2001 Rainville et al., 2005). It should be noted however that such research tends to consider the emotional state prior to the experience of pain rather than the emotional response to noxious stimuli (Rainville, Bao Chrtien, 2005).Another explanation for the hypoalgesic effect of swearing could be the role of the amygdala in the fight or flight response. The central nucleus of the thoroughfare p rojects to the hypothalamus which then triggers the sympathetic nervous system resulting in the fight or flight response of raised heart rate and blood pressure (Wickens, 2009). This response can be activated by a number of different stimuli including pain and can increase pain tolerance and decrease the perception of pain. moreover activation of the amygdala, such as through swearing, may increase physiological reactions further resulting in this mechanism being even more effective against pain. interdict emotions such as anxiety and depression have received a lot of attention in the field of pain research. It is becoming apparent that other negative emotions, such as anger, fear and aggression may also be involved in the perception of pain (Quartana, Bounds, Yoon, Goodin Burns, 2010). Aggression is one of the negative emotions that have been suggested to be linked to swearing (Stephens Umland, 2011). Many studies have been conducted in the past on whether pain elicits aggressio n, but there has been little research into whether aggression as a trait has an effect on pain tolerance and pain perception. In a study conducted by Seguin, Pihl, Boulerice, Tremblay Harden (1996) adolescent boys were asked to take part in a pain tolerance task assessed via finger pressure pain. Trait aggression was disced as stable, unstable or no history. The results suggested that boys classed as unstable aggressors displayed the lowest pain tolerance, whereas boys classed as stable aggressors displayed the highest pain tolerance. Another study found that male participants who displayed higher levels and frequency of aggression could comport longer periods of pain compared to males with lower levels of aggression (Niel, Hunnicut-Ferguson, Reidy, Martines Zeichner, 2007). This seems to suggest that aggression does, in some way, play a role in pain tolerance. The main aftermath arising from these studies is that they only included male participants. A more recent study lookin g at a sample of both males and females found no significant relationship between pain tolerance and trait aggression once the mens conformity to a masculine gender role had been controlled for (Reidy, Dimmick, MacDonald, Zeichner, 2009). These conflicting results highlight the need for further research into the role of trait aggression in the experience of pain alongside the effects of swearing and including both male and female participants.The amygdala has already been mentioned in connection with pain modulation, swearing and emotion however it has also been linked with trait aggression. In a recent study 20 volunteers underwent brain scans which revealed a significant negative correlation between trait aggression and amygdala volume (Matthies, Rusch, Weber, Lieb, Phillipsen, Tuescher et al., 2012). Due to this and the previous inconclusive research into the role of trait aggression and pain, a high/low trait aggression condition will be included in the current study to see if there is any fundamental interaction between trait aggression and swearing during the cold pressor task.The main aim of the current study is to try and replicate the results found by Stephens et al. (2009 2011). A cold pressor task will be used as the noxious stimuli with swearing, gender and trait aggression being compared with regards to cold pressor latency. Heart rate will be record as in Stephens et al. (2009 2011) but the current study will also record systolic and diastolic blood pressure. These physiological responses were not measured in the original studies on swearing and pain and would provide more evidence that the sympathetic nervous system is activated to a greater degree whilst swearing as well as giving more insight into the blood pressure and pain relationship (Helfer McCubbin, 2001 Poudevigne, OConner Pasley, 2002).Based on previous research several hypotheses were generated. In line with the findings of Stephens et al. (2009 2011) it is hypothesised that cold p ressor latency will be longer in the swearing condition compared to the non-swearing condition for males and females. It is also expected that physiological responses (systolic/diastolic blood pressure and heart rate) will be higher in the swearing condition compared to the non-swearing condition. Additionally, males are expected to withstand the noxious stimulus (cold pressor task) for longer than females across the swearing and non-swearing conditions. In line with Stephens et al. (2009), but not Stephens Umland (2011) it is hypothesised that females will display a greater increase in heart rate (and therefore systolic and diastolic blood pressure) in the swearing condition in comparison to the males.HypothesisIn line with Stephens et al., (2009 2011)Cold pressor latency will be longer in the swearing condition compared to the non-swearing condition for males and females.Systolic blood pressure will be higher in the swearing condition compared to the non-swearing condition for ma les and females.Diastolic blood pressure will be higher in the swearing condition compared to the non-swearing condition for males and females.Heart rate will be higher in the swearing condition compared to the non-swearing condition for males and females.Overall males will withstand the noxious stimulus (cold pressor task) for longer than females across the swearing and the non-swearing conditions.In line with Stephens et al., (2009), but not Stephens Umland (2011)Females will display a greater increase in heart rate (and therefore systolic and diastolic blood pressure) in the swearing condition in comparison to the males.Due to the inconclusive research into the role of trait aggression and pain tolerance no specific hypothesis will be generated for this variable. Instead it will be examined whether trait aggression will have any effect on systolic blood pressure, diastolic blood pressure, heart rate and cold pressor latency across the swearing and non-swearing conditions and als o whether there are any gender differences.METHODDESIGNA 2 x 2 x 2 mixed subjects design was employed for this study. The between subjects factors were gender (male/female) and trait aggression (high/low). The within factor was swearing with all participants taking part in both the swearing and the non-swearing condition. The order of conditions (swearing/non-swearing) was counterbalanced for each participant. The dependent variables measured were systolic blood pressure (mmHg), diastolic blood pressure (mmHg), heart rate (BPM) and cold pressor latency (length of time participants kept their hand in the cold water in seconds). The cold pressor task was employed as the painful stimulus. To avoid demand effects participants were not informed of the true character of the task until they were debriefed.PARTICIPANTSThe participants consisted of 50 students attending various courses at the University of Central Lancashire. They were recruited using both opportunity sampling and through th e research participation pool where students receive credit for taking part in research. Participation was entirely voluntary. There were 25 females and 25 males with ages ranging from 18 to 44 years. Mean age was 23.4 years (SD = 5.71). Participants were screened for quick heart conditions, high/low blood pressure and circulatory problems. No participants were excluded from the study on the basis of this screening.MATERIALSPrior to taking part in the study, participants were disposed a brief sheet (see vermiform process 1 for brief) and screened using a health screening questionnaire provided by the University of Central Lancashire (see Appendix 2 for Health covert Questionnaire). For the Cold Pressor Task a bucket filled with a mixture of cold water and ice was used. Prior to each task a thermometer was used to check the temperature was 0C. For baseline readings and between tasks a bucket containing room temperature water (25 C) was used. Physiological readings were obtained u sing a LifeSource UA-767 Plus machine which measures both blood pressure (systolic and diastolic) and heart rate.Trait aggression was measured using a trait aggression questionnaire (Buss Perry, 1992). This questionnaire consists of 29 items which participants rank on a likert scale of one to five with one being not at all like you and five being completely like you. Examples of statements are Once in a while I cant control the urge to strike another person and I tell my friends openly when I disagree with them. indoors the questionnaire are four subscales which measure verbal aggression, physical aggression, hostility and anger. For the purposes of this study the overall trait aggression score was used where a higher score on the questionnaire equals a higher level of trait aggression. The questionnaire has been shown to have good internal consistency ( = .89) as well as test-retest reliability (r = .80 Buss Perry, 1992). (See Appendix 3 for Trait Aggression Questionnaire). Afte r completing the aggression questionnaire participants were made fully aware of the nature of the study through the debrief (see Appendix 4 for debrief).PROCEDUREFor the task students individually attended a research laboratory on campus at the University of Central Lancashire. They were informed that the study would be looking into physiological responses to the cold pressor task and asked to complete a health screening questionnaire. Following this participants were asked to make themselves comfortable whilst the blood pressure/heart rate calamity was placed around their non-dominant arm before submerging their dominant hand up to the wrist in a bucket of room temperature water for trine minutes. At the end of the threesome minutes a baseline blood pressure and heart rate reading were put down. Participants were then asked for what swear word they would use if they were to bang their thumb with a hammer and also what word they would use to describe a chair. Whilst repeating th eir chosen word for either cursing or chair, participants submerged their dominant hand in the cold water. They were given the instruction to keep their hand in the water until it became too uncomfortable or painful. A time limit of three minutes was imposed due to safety reasons and 11 participants reached the limit in one or both conditions. During the task, heart rate and blood pressure were recorded every 30 seconds. Once they removed their hand they were asked to submerge it back in the bucket of room temperature water for three minutes. Following this participants were asked to repeat the initial cold pressor task, this time repeating the chosen word not used in the first condition. Order of conditions was counter-balanced for all participants.Following both cold pressor tasks participants were asked to complete the aggression questionnaire before being fully debriefed. The trait aggression questionnaires were scored and then a median give out performed. Possible trait aggres sion scores range from 29 145. Participants in this study scored from 49 113 with a median of 69.5. Trait aggression was then split into high or low, with high being equal to, or more than 69.5, (n25) and low being less than 69.5 (n25). The research was conducted with the approval of the ethics committee at the University of Central LancashireThe research was conducted with the approval of the ethics committee at the University of Central LancashireRESULTSFor the purpose of outline, averages were taken of the systolic, diastolic and heart rate readings for male and female participants with high and low trait aggression in each condition (swearing/non-swearing). Cold pressor latency was recorded in seconds. the trait aggression questionnaires were scored and then a median split performed. Possible trait aggression scores range from 29 145. Participants in this study scored from 49 113 with a median of 69.5. Trait aggression was then split into high or low, with high being equal to, or more than 69.5, (n25) and low being less than 69.5 (n25). (For raw data distinguish to Appendix 5)The effects of swearing/aggression on systolic blood pressure during the cold pressor taskSystolic blood pressure (mmHg) was recorded during the cold pressor task. remand 1 shows the means and standard deviations of systolic blood pressure during the swearing and non-swearing conditions for high/low trait aggressive males and females.Table 1 Means (and standard deviations) of Systolic Blood Pressure (mmHg) across swearing/non-swearing conditions for high/low trait aggressive males/females.HIGH AGGRESSION low-down AGGRESSION replete(p) expressMALE125.24(20.95)129.21(16.05)127.15(18.48)FEMALE123.31(12.45)119.81(11.65)121.49(11.92)TOTAL124.31(17.07)124.32(14.45)124.32(11.92)NON SWEARINGMALE121.45(16.46)129.48(19.54)125.30(18.09)FEMALE119.33(13.77)116.44(11.28)117.82(12.36)TOTAL120.43(14.95)122.70(16.82)121.56(15.79)A 2 (trait aggression high/low) x 2 (gender male/female) x 2 (swea ring/non-swearing) mixed subjects factorial analysis of variance revealed no significant main effect of swearing condition on systolic blood pressure (F(1,46) = 1.57, p = 0.217, Eta = 0.033). There was a non-significant main effect of gender (F(1,46) = 2.95, p = 0.093, Eta = 0.060) and a non-significant main effect of trait aggression (F(1,46) = 0.13, p = 0.718, Eta = 0.003). In addition, the interaction between swearing and trait aggression showed no significance (F(1,46) = 0.29, p = 0.593, Eta = 0.006). The interaction between swearing and gender was non-significant (F(1,46) = 0.19, p = 0.662, Eta = 0.004) as was the interaction between gender and trait aggression (F(1,46) = 1.42, p = 0.240, Eta = 0.030). Overall there was no significant 3-way interaction between swearing, gender and trait aggression (F(1,46) = 0.16, p = 0.691, Eta = 0.003). (For analysis output on systolic blood pressure see Appendix 6).The Effect of swearing/aggression on diastolic blood pressure during the cold pressor taskDiastolic blood pressure (mmHg) was recorded during the cold pressor task. Table 2 shows the means and standard deviations of diastolic blood pressure during the swearing and non-swearing conditions for high/low trait aggressive males and females.Table 2 Means (and standard deviations) of Diastolic Blood Pressure (mmHg) across swearing/non-swearing conditions for high/low trait aggressive males/females.HIGH AGGRESSIONLOW AGGRESSIONTOTALSWEARINGMALE78.73(17.66)87.37(12.75)82.88(15.81)FEMALE85.63(9.85)79.50(16.37)82.44(13.72)TOTAL82.04(14.58)83.28(14.99)82.66(14.65)NON SWEARINGMALE80.56(13.05)86.24(13.05)82.88(15.81)FEMALE85.21(8.81)85.74(10.06)85.49(9.29)TOTAL82.79(11.24)85.98(11.78)84.39(11.51)A 2 (trait aggression high/low) x 2 (gender male/female) x 2 (swearing/non-swearing) mixed subjects factorial ANOVA revealed no significant main effect of swearing condition on diastolic blood pressure (F(1,46) = 0.65, p = 0.425, Eta = 0.014). There was a non-significant main effe ct of gender (F(1,46) = 0.07, p = 0.801, Eta = 0.001) and a non-significant main effect of trait aggression (F(1,46) = 0.48, p = 0.491, Eta = 0.010). In addition the interaction between swearing and trait aggression showed no significance (F(1,46) = 0.21, p = 0.651, Eta = 0.004). The interaction between swearing and gender was non-significant (F(1,46) = 0.40, p = 0.531, Eta = 0.009) as was the interaction between gender and trait aggression (F(1,46) = 2.51, p = 0.120, Eta = 0.030). Overall there was no significant 3-way interaction between swearing, gender and trait aggression (F(1,46) = 1.41, p = 0.241, Eta = 0.030). (For analysis output on diastolic blood pressure see Appendix 7).The Effect of swearing/aggression on heart rate during the cold pressor taskHeart rate (BPM) was recorded during the cold pressor task. Table 3 shows the means and standard deviations of heart rate during the swearing and non-swearing conditions for high/low trait aggressive males and females.Table 3 Mean s (and standard deviations) of heart rate (bpm) across swearing/non-swearing conditions for high/low trait aggressive males/females.HIGH AGGRESSIONLOW AGGRESSIONTOTALSWEARINGMALE83.79(11.45)81.93(15.86)82.90(13.48)FEMALE92.10(16.79)87.34(16.14)86.92(16.29)TOTAL87.78(14.59)84.74(15.91)86.26(15.19)NON SWEARINGMALE84.57(20.16)84.91(16.13)84.73(17.96)FEMALE89.88(12.40)85.17(16.42)87.43(14.53)TOTAL87.12(16.76)85.04(15.94)86.08(16.22)A 2 (trait aggression high/low) x 2 (gender male/female) x 2 (swearing/non-swearing) mixed subjects factorial ANOVA revealed no significant main effect of swearing condition on heart rate (F(1,46) = 0.01, p = 0.934, Eta = .000). There was a non-significant main effect of gender (F(1,46) = 1.40, p = 0.243, Eta = 0.030) and a non-significant main effect of trait aggression (F(1,46) = 0.46, p = 0.503, Eta = 0.010). In addition the interaction between swearing and trait aggression showed no significance (F(1,46) = 0.09, p = 0.770, Eta = 0.002). The interaction be tween swearing and gender was non-significant (F(1,46) = 1.14, p = 0.292, Eta = 0.024) as was the interaction between gender and trait aggression (F(1,46) = 0.24, p = 0.628, Eta = 0.005). Overall there was no significant 3-way interaction between swearing, gender and trait aggression (F(1,46) = 0.08, p = 0.780, Eta = 0.002). (For analysis output on heart rate see Appendix 8).The Effect of swearing/aggression on cold pressor latency during the cold pressor taskCold pressor latency (the length of time participants kept their hand in the ice water) was recorded in seconds. Table 4 shows the means and standard deviations of cold pressor