8.2 The Study: Psychopathy and Pain Tolerance
Psychopathy is a trait marked by reduced empathy, emotional response, and behavioural control. Past research has demonstrated a positive association between psychopathy and higher pain tolerance. Some researchers believe that a higher tolerance for physical pain may be linked to a lack of empathy and willingness to harm others, which are characteristic traits of people with high levels of psychopathy. At the same time, most research on psychopathy has used samples of incarcerated people, and there has been relatively little attention paid to psychopathy within the general (i.e., non-incarcerated) population. The goal of this study is to investigate the association between psychopathy and pain tolerance in a non-incarcerated sample.
8.2.2 Procedure
Participants will be 110 undergraduate students recruited through SONA. This study will be completed in-person under the supervision of a trained research assistant. After providing informed consent, participants will respond to a questionnaire which includes questions about demographic characteristics and a measure of psychopathy. They will then be fitted with a heart rate monitor and their baseline heart rate will be established. Participants will then complete a cold pressor test. They will be compensated for their time by receiving course credit in a participating course.
8.2.3 Measures
Psychopathy will be measured using the Levenson Self-Report Psychopathy Scale (LSRP). The LSRP was designed to measure psychopathy in non-institutionalized settings (Levenson & Fitzpatrick, 1995). It is free to use and simple to administer. Participants report their agreement with 26 statements, using the response options: 1 (disagree strongly), 2 (disagree somewhat), 3 (agree somewhat), and 4 (agree strongly). Some items are reverse-coded, and then all items are summed to produce a composite measure of psychopathy. Levenson & Fitzpatrick (1995) proposed the following cut-offs:
- 0–48: non-psychopathic,
- 49–57: mixed,
- ≥58: psychopathic.
Pain tolerance will be measured using a cold pressor test. The cold pressor test is a standardized and widely used measure of pain tolerance. Participants are asked to submerse one hand in a cold water container (3–4 °C) for as long as they can. They are instructed to inform the research assistant as soon as they begin to feel pain and to remove their hands from the cold water when the pain becomes intolerable. Each participant’s pain tolerance is the amount of time between reporting first feeling pain and removing their hand from the water.
8.2.4 Analytic Strategy
We will conduct a directional null hypothesis significance test of the simple bivariate correlation between LSRP total scores and pain tolerance at the traditional \(\alpha\) = .05.
8.2.5 Sample Size and Power Analysis
We plan to recruit 110 participants to complete this study. This is based on a power analysis that identified N = 101 is required to for 95% power if the population effect size is r \(\ge\) .32. This effect size corresponds to approximately 10% shared variance between two variables. We are aiming to recruit 110 participants to allow for the possibility that some participants may need to be excluded from analysis (e.g., if data are missing).