Physiology of Behaviour; Sex differences in physiological responses of the cold pressor test. Abstract This lab report aims to analyse the sex differences in a physiological responses to a potentially aversive physiological stress inducing stimuli. This was conducted by a cold pressor test. 8 males and 8 females participated. Heart rate, respiration rate, and galvanic skin was recorded whilst participants undertook the CPT test. Results showed no significant differences that there is a gender difference in experimental induced stimuli of pain. Introduction
To say that male and females are biologically and physiologically the same is denying physical reality’s differentiation takes place immediately as the male or female begins to develop within the womb. The sex hormones --primarily oestrogen and testosterone--have a significant impact on the behaviour of males and females. Why do boys typically like to play with trucks and girls like to play with dolls? Feminists usually claim this is the result of socialization, but there is growing scientific evidence that boys and girls are greatly influenced by their respective hormones.
Within biological psychology the biology and physiological differences are studied thoroughly between male and female. In biological psychology, physiological pain has been studied frequently. Furthering this, the differences between male and female pain response and threshold for pain have been measured in several experiments. Pain is often described as an uncomfortable response to unpleasant stimuli. Different physiological responses take place when pain is perceived.
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The International Association for the Study of Pain's widely used definition states: "Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage". (Bonica,1979) Pain motivates the individual to remove themselves from these unpleasant stimuli or situations, to protect the body. Pain is a part of the body’s defence system. Humans attempt to avoid similar painful and unpleasant experiences in the future. (Lynn,1984)Most pain resolves promptly once the painful stimulus is removed and the body has healed, but sometimes pain persists despite removal f the stimulus and apparent healing of the body; and sometimes pain arises in the absence of any detectable stimulus, damage or disease. (Raj,2007) People report a pain threshold and a pain tolerance. The pain threshold is the point at which sensation becomes pain, where as Pain tolerance is the amount of pain a person can handle without breaking down, either physically or emotionally. Men and women have reported over several studies different measures of pain threshold and pain tolerance in this following study I aim to review the literature between the sex differences of men and women in line with pain tolerance and pain threshold. Previous tests for pain threshold and tolerance that have been used are the electric shock test, tooth pulp stimulation, and tourniquet induced scheme (von Baeyer, 2007. ) The pain experiment that will be used in this lab report is the cold pressor test. The cold pressor test is a cardiovascular test performed by immersing the hand into an ice water container, usually for one minute, and measuring changes in blood pressure and heart rate. Its response is clinically indicative concerning vascular response and pulse excitability.
The cold pressor test has been used for several years as a means of measuring experimentally induced pain. The cold pressor test is a preferred method to experimentally induce pain. Even though inducing pain seems unethical, as it is a necessity for psychological research, this method is preferred. It does not cause any psychology damage, it does not cause any damage to tissue or limbs, and minimum means of stimulation is used in comparison to other experimental induced pain methods. Methodology needs to be clear and concise for carrying out the cold pressor test to be accurate.
Temperature of the water is important to take into consideration when carrying out the cold pressor test, as temperature activates the sympathetic nervous system to release physiological responses. In a study researching the difference that the temperature of the water can make to the results showed significant outcomes. Twenty-six participants (12 men, 14 women) underwent 4 cold pressor trials with temperature order counterbalanced across 1°C, 3°C, 5°C, and 7°C, temperatures representative of the range used in previous literature.
Significant main effects of temperature were found for tolerance time, with higher temperatures resulting in longer times, and pain intensity, with lower temperatures resulting in higher intensities. Gender differences were obtained, with men tolerating the stimulus for significantly longer than women. Mitchell et al has found that water variations in CPT pain response in adults elicited by temperature variations of as little as 2°C. The local warming changes the pain stimulus, enhancing the likelihood of longer tolerance.
In conclusion, small differences in water temperature have a significant effect on pain intensity and tolerance time. Methodology has to be carefully followed to ensure that the water temperature does not change across the study as very minor changes in experimental protocol can produce significant differences in the cold pressor test. (Mitchell, 2004). Other measures can also be obtained from the cold pressor such as pain threshold and pain tolerance. (Lowery, 2006)This is done by requiring a participant to place their hand in the cold pressor for as long as they can.
Once pain is present, they let the researcher know. Once the pain is unbearable, the participant removes his/her hand. This provides a measure of threshold (first feeling pain) and tolerance (total time minus threshold). Within the human race, the vast majority of studies obtained results that women are more sensitive than men to experimentally induced pain, as evidenced by the cold pressor test. (Dixon, 2004) In a meta-analysis of 17 studies, Riley et al (1998) found that the effect sizes for sex differences in pain threshold and tolerance were moderate to large.
Nevertheless, different experimenters suggested that these sex differences might not be as strongly supported. (Berkley, 1997) In their 1995 review, Fillingim and Maixner summarized 34 human studies. In 24 of these studies, men exhibited less pain than women, but sex differences were reported in only one of several measures or conditions examined in 7 of the 24 studies. .) In 10 of the 34 studies, sex differences were not found. . (Fillingim, 1995). The menstrual cycle plays a big part in the explanation of gender differences of pain tolerance and threshold.
Studies have previously shown that higher oestrogen levels produce a greater pain perception. One study analysed the difference using the cold pressor test where 22 female students participated at two different phases of the menstrual cycle (days 2–4 and days 20–24). A control group of nineteen male students participated on two occasions, separated by a three week period were used. The results showed that men have a higher pain threshold than women, and women seemed to have a greater threshold for pain in the second period of their cycle. (Helstrom, B. amp; Lundberg, U. 2000) After reviewing and assessing the literature relating to gender differences in pain using the cold pressor test, we have decided to test the following 3 hypotheses; 1. Females and males will differ in pain threshold. 2. Females and males will differ in tolerance to pain. 3. There will be sex difference in physiological stress response (as measured by heart rate, respiration rate, and galvanic skin response) Participants The participants used were a random sample of 8 males and 8 females within an age range of 18-23. The mean age was 20.
No participants were wearing tights or clothing that would disrupt the results of the physiological measures All subjects were assumed as English as a first language therefore understanding the instructions of the experiment. All subjects did not suffer from any medical issues outlined in the medical history form which included Reynaud’s Syndrome, high or low blood pressure, diabetes or epilepsy, recent injury or surgery, neurological illness, chronic pain or any type of pain that might influence the results of the experiment. Materials One bucket of iced water at 20% of ice and 80% of water.
A towel was used, a biopac physiological recording unit, a computer, a thermometer, electrode pads, timers, and recording sheets. Procedure Experimenters set up the lab, got ice for the bucket and measured the temperature of the water being between 3-5 degrees using a thermometer. The biopac was opened on the computer and electrode pads were set up to be ready for use. Participants were recruited, and asked to read the information sheets and sign the consent forms. Then the participants were brought into the lab where they were then hooked up to the biopac. Electrode pads were placed on the finger, wrist, and ankles.
An experiment then explained to the participant the procedure. Participants were asked to take a deep breath when they heard the calibrate button, then a to relax for 2 minutes as a baseline was taken. The participants were then told that they would place their hands in a bucket of iced water. They were told when they began to felt pain say ‘uncomfortable’ and when they could not uphold a further threshold to say ‘stop’. Participants were facing away from the computer so they could not see the recordings. The experimenters then calibrated the biopac as the subject took a deep breath.
The experimenters then recorded a baseline measurement of the participants GSR, Heart rate, and respiration. After 2 minutes the participants were then asked to place their hands in the ice bucket of water and the experimenters then measured tolerance and thresholdThe participants were then given a towl to watm their hands and they were debriefed. Experimenters then took note of the results from the GSR, heart rate and respiration rate from the baseline measurement, when the participant said ‘uncomfortable’ and when the participant said ‘stop’. The data was then analysed through means of SPSS. Results Hypothesis 1
When reviewing the overall mean for the differences in male and female response to pain threshold, there was different means found; Females 28. 0 Males; 45. 8. The hypothesis that females and males will differ in pain threshold scores was tested by means of a t-test for independent group samples. The results were as follows; t=1. 83 df=10 p;0. 98, 2tailed. The hypothesis was therefore not upheld. There was no significant difference between the pain threshold scores and gender. Hypothesis 2 When reviewing the overall mean for the differences in male and female results for tolerance to pain; the following means were obtained Females; 110. Males; 45. 8. The hypothesis that females and males will differ in tolerance to pain scores was tested inferentially by means of a t-test for independent group samples. The following results were obtained t=1. 16, df=10, p;0. 273. The hypothesis was therefore not upheld. There was no significant difference between pain tolerance scores and gender. Hypothesis 3 A 2 way ANOVA was carried out to asses the sex differences in physiological responses. The results showed no significant differences in relation to sex differences in Heart Rate df=1, f=. 066, p=. 802, GSR- df=1, f=. 534, p=. 82, and Respiration rate- df=1, f=. 410, p=. 885 Discussion The results that were collected from the data did not support any of the 3 hypotheses. This can be due to several different reasons. Our results were in line with several different studies, where sex differences were not found in pain tolerance and pain threshold. .) In 10 of the 34 studies reviewed, sex differences were not found to be statistically significant. (Fillingim, 1995). However, other studies have found that gender differences did support significant results. . In 24 studies reviewed by Riley et al, men exhibited less pain than women.
Several variables in different studies have been taken into account which produces different outcomes of results. In several studies, it shows that hunger can be important in the threshold and tolerance of pain. One study reported the effects of 2, 10, 14, and 24 hr. of food deprivation (hunger) and of 0, 2, 3, and 4 min. of cold-pressor stimulation. This study found that the relationship between intensity of hunger and level of autonomic response is not linear and that there seemed to be no gender difference between hunger and pain. (Engel, 1959). Personality factors have also shown in some studies to show a difference in pain perception.
This study effects of personality and pain catastrophizing upon pain tolerance and pain ratings and to examine the impact of an experimental pain induction on subsequent ratings of catastrophizing. The results found were t that sex differences in catastrophizing and pain responsivity are partially accounted for by the dispositional tendency to describe oneself as emotionally vulnerable. Females tended to describe themselves more emotionally vulnerable than males resulting in males having a higher threshold for pain. (Thorn, 2004). Anxiety can also possibly play a part in the effects of a cold pressor test.
It has been found that anxiety based situations can provoke a higher intensity of pain. In Jones (2002) they found that, contrary to previous results, that men had a higher rating of intensity of pain in anxiety provoked situations compared to women. A major issue that has been addressed in the introduction plays a big role to why women can possibly have a higher intensity of pain compared to men. Previous studies have found that it can depend what time in the menstrual cycle that women are in can have an effect on their ratings and perceptions of pain.
The hormone oestrogen seems to produce a higher sensitivity to pain and when conducting the cold pressor test this is a serious issue to be taken into consideration. evaluated sex differences in response to cold pressor pain in normally menstruating women (NMW), women maintained on oral contraceptives (OCW), and men. Testing occurred during 5 phases of the menstrual cycle. All participants completed 10 sessions (2 sessions per phase). During the cold presser test, participants immersed the forearm into water maintained at 4°C, and pain threshold and tolerance were measured.
The results were analysed and the study supports the notion that differences in pain perception between the sexes and among menstrual cycle phases are subtle. However, normally menstruating women showed an increase in pain tolerance and threshold over repeated stimulation, whereas men only exhibited a minor increase in pain threshold, therefore it shows a sex difference in reaction to repeated painful stimuli between men and women. Following our results, it is believed that our results could have been implicated due to the distractions of the participants.
The cold pressor test was conducted in a lab where there was other cold compressor tests being conducted, therefore with the level of noise it was easy to be distracted. This can be an issue for methodology. A previous study has undertaken a study on how distraction can affect experimental pain results. The results were found that distraction had varying impact on different aspects of pain responding, and affectively neutral distraction during pain stimulation reduced the sensory pain ratings but not pain tolerance.
Affectively neutral distraction may be used to manage a patient's reaction to brief, painful stimulation, but may not work in long term chronic pain (Hodes, 1990). Also as discussed in the introduction, temperature is an extremely important methodological factor when carrying out the CPT. In this experiment we found it very difficult to keep a perfect modulation of the temperature. Previous studies have shown that this minor glitch in the experiment can have an affective major impact on the results. Although water temperature only had risen to an extra one degree, this should be still taken into account for the outcome of the results.
Within our sample size, we obtained 16 subjects. (8 males and 8 females). Although the results are weighted, one can feel that this is too small a sample size to draw correct inferences and conclude from. In the future a bigger sample size should be obtained as there will be a greater sensitivity to the results and different results could possibly have an outcome. In continuation with the methodology implications of the participants, they should of not known what the experiment was about. Some of the subjects stated after the experiment that they already knew this experiment via the media.
Therefore, participants could of possibly tried to withstand a threshold for longer as they knew what exactly the experimenters were testing. As the experimenters were all female, in sociological aspects, men could have possibly pretended to not feel pain, in order to impress the experimenters. This can affect the results to an extent. There also could be an implication of anticipation of pain versus actual pain. If the subject is anticipating feeling pain, this can make them think that they feel more pain as they have psychologically believed that this experiment will amount to a certain level of pain.
Even though some would conclude that inducing pain and stressors on individuals is ethically wrong, psychology needs a mean to test experimental pain for a growth in psychology. The cold pressor test was the best test to carry out to induce pain as it does not cause any psychological or physiological harm, the participants’ control over the process (i. e. , their ability to withdraw the limb), and the pain only mounts very slowly, the subject can withdraw their hand if it reached a level of any severe pain.
After analysing and assessing various discursive points and implications of the study, this study can conclude that there are methodological implications within the cold pressor test. Different studies all have different outcomes on whether there is an actual sex difference within pain tolerance and pain threshold, and this can be due to different variables being used within studies. Further research should progress in the areas of the affect of a difference in water temperature, and anxiety provoked situations in relation to gender difference as there has been previously little research conducted.
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