Behavioral assessment of pain detection and tolerance in monkeys

Cebus albifrons monkeys received electrical stimulation of the hindlimbs over a wide range of intensities. On trials signalled by a blue light, the animals were permitted to escape shock by pressing a disc, or shock was terminated after 8 sec (free escape). Escape force (disc pressure) was found to increase as stimulation intensity increased well beyond escape threshold, while shock duration curves reached plateau at the mid-range of intensities. The shock duration curves generated by free escape responses should be comparable to pain detection functions obtained by similar operations in humans, and the curves were stable over months of testing, as is generally found in pain-detection studies. On trials signalled by a red light, the animals received intense tail shock immediately after escape responses (punished escape), or, if they endured leg shock for 8 sec without escaping, then they could avoid tail shock with a panel press. The shock duration curves generated by punished escape responses should be comparable to pain tolerance functions as defined for human subjects, and the escape thresholds were considerably higher on red-light trials. As in human studies, the tolerance curves were not stable over repeated testing sessions, and some feature of the paradigm forced a progression toward extremely high levels of tolerance.     

Effects of suppression, acceptance and spontaneous coping on pain tolerance, pain intensity and distress

Wegner's Theory of Ironic Processes has been applied to study the effects of cognitive strategies to control pain. Research suggests that suppression contributes to a more distressing pain experience. Recently, the acceptance-based approach has been proposed as an alternative to cognitive control. This study assessed the tolerance time, the distress and the perceived pain intensity in three groups (suppression, acceptance and spontaneous coping groups) when the participants were exposed to a cold pressor procedure. Two hundred and nineteen undergraduates volunteered to participate. The suppression group showed the shortest tolerance time and the acceptance group showed the longest tolerance time. The acceptance group showed pain and distress immersion ratings that were significantly lower than in the other two groups, between which the differences were not significant. In the first recovery period, the suppression group showed pain and distress ratings that were higher than in the other two groups. In the second recovery period, although the acceptance group showed pain and distress ratings that were significantly lower than in the other two groups, the suppression and the spontaneous coping groups did not differ. The presence of a 'rebound' of physical discomfort and the effects of suppression on behavioural avoidance are discussed. These results support the acceptance approach in the management of pain.     

Alone but feeling no pain: Effects of social exclusion on physical pain tolerance and pain threshold, affective forecasting, and interpersonal empathy

Prior findings of emotional numbness (rather than distress) among socially excluded persons led the authors to investigate whether exclusion causes a far-reaching insensitivity to both physical and emotional pain. Experiments 1-4 showed that receiving an ostensibly diagnostic forecast of a lonesome future life reduced sensitivity to physical pain, as indicated by both (higher) thresholds and tolerance. Exclusion also caused emotional insensitivity, as indicated by reductions in affective forecasting of joy or woe over a future football outcome (Experiment 3), as well as lesser empathizing with another person's suffering from either romantic breakup (Experiment 4) or a broken leg (Experiment 5). The insensitivities to pain and emotion were highly intercorrelated.     

Cognitive mediators of pain perception and tolerance

A social learning model of pain perception and tolerance was evaluated. Responses to cold-pressor pain were examined in 4 groups of 20 Ss each. One group was given instruction in cognitive coping strategies, the 2nd was given a monetary incentive contingent on tolerance time, the 3rd was given both cognitive training and monetary reinforcement, and a no-treatment control group was given neither. Incentive and coping instructions significantly increased tolerance but did not alter pain perception. A path analysis indicated that pain tolerance was affected by self-efficacy, which in turn was predicted by pain expectancy and the provision of incentives. Incentive also had an impact on tolerance that was independent of self-efficacy. Pain perception was strongly affected by pain expectancy, but was unrelated to self-efficacy.     

Hypnosis, suggestion, and placebo in the reduction of experimental pain

Two experiments compared placebo and hypnotic analgesia in high and low hypnotizable subjects. Experiment 1 demonstrated that hypnotic and placebo analgesia were equally ineffective in low hypnotizables, but that hypnotic analgesia was much more effective than placebo analgesia in high hypnotizables. Experiment 2 replicated these results, but also included low and high hypnotizables who were given a nonhypnotic suggestion for analgesia. Both the low and high hypnotizables in this group reported greater suggested than placebo analgesia and as much suggested analgesia as high hypnotizable hypnotic subjects. Both experiments found substantial discrepancies between the amount of pain reduction subjects expected from the various treatments and the amount of pain reduction they actually reported following exposure to those treatments. In Experiment 2, subjects in all treatments who reduced reported pain engaged in more cognitive coping and less catastrophizing than those who did not reduce pain. Theoretical implications are discussed.     

Visual stimuli in distraction strategies for increasing pain tolerance

Recent experimental studies in pain control have questioned the value of pleasant affect in strategies employing distraction. It appears that pleasant affect may have been systematically confounded with task complexity or novelty in past research that found pleasant imagery or slides effective in increasing pain tolerance with the cold pressor test. The present study was a follow-up to a study conducted by this author (Greenstein, 1984) in which unpleasant slides had significantly increased pain tolerance above pleasant slide level. In the present study, 69 college students (35 females, 34 males) rated either the pleasant or unpleasant slides used in the original study on their perceived pleasantness, complexity, and uniqueness (novelty). Results indicated that the unpleasant slides were rated significantly more complex (P<0.001) and unique (P<0.001) than the pleasant slides. Additionally, as in the earlier study, ratings of the unpleasant slides on pleasantness deviated significantly farther from neutrality than did ratings of the pleasant slides (t=5.04,P<0.001). Thus the unpleasant slides were also perceived as being more significant (i.e., pertinent) than were the pleasant slides. The results indicate that affect was confounded with other stimulus characteristics in the Greenstein (1984) pain control study and probably in a significant number of other studies as well. Researchers are cautioned to control for the stimulus characteristics of visual distraction strategies used in pain control studies. The assumption that pleasantness,per se, contributes to strategy effectiveness is no longer tenable; future research must demonstrate an independent effect. Further, the implication that stimulus significance may increase the effectiveness of distraction strategies opens up a potentially fruitful avenue of research in pain control.     

Relationship of pain tolerance with human aggression

In research with animals as well as samples of chronic pain patients and elderly persons, pain has been positively correlated with measures of irritability, hostility, and aggression. The present investigation examined the relationship of pain tolerance with aggression. 72 men participated in the Response Choice Aggression Paradigm, described previously by Zeichner and colleagues, in which aggressive response to provocation was possible but not required of participants. Subjective pain tolerance, defined as maximal electrical shock willingly tolerated by participants, was assessed. Significant but small Pearson product-moment correlations between pain tolerance and aggression ranged between .21 and .32, with the largest accounting for 9% of variance.     

Alexithymia is not related to tolerance for cold pressor pain

To test the hypothesis that higher scores on alexithymia are associated with reduced tolerance for cold pressor pain, 116 college undergraduates completed the Toronto Alexithymia Scale-20 of Bagby, Parker and Taylor and engaged in the cold pressor test. Their alexithymia scores were not associated with tolerance for cold pressor pain, suggesting that individuals scoring high on alexithymia do not show a general hypersensitivity to a cold stimulus.     

After images and pain tolerance: a descriptive study on their interrelationship

After images are based on physiological processes, they can also be treated as subjective phenomena with a psychological meaning. This statement also applies to pain. The basic working hypothesis of this study concerned the relationship between the two phenomena. Forty-one respondents (23 females, 18 males, age range 20-45 years) were given the Cold Pressor Test and the Serial After Image Technique. The data analysis was done by means of cross-tables and an exploratory optimal scaling program (OVERALS). Three pain tolerance groups (low, medium, high) could be differentiated fairly well on the basis of the after image characteristics of the respondents. Pain intolerant respondents more frequently had small and "immature" after images, whereas highly pain tolerant respondents had more large and "mature" after images. The implications of these results for a bio-psycho-social theoretical frame of reference for pain are discussed.     

Self-efficacy and perceived control: cognitive mediators of pain tolerance

The cold-pressor task was used with 102 female undergraduates in 2 experiments to determine (a) whether self-efficacy has validity as a true causal determinant of behavior change or is a correlate of change that has already occurred and (b) how perceptions of control and self-efficacy interact to determine choice behavior, persistence, and the impact of an aversive stimulus. Results of Experiment 1 indicate that self-efficacy expectations affected performance beyond what would have been expected from past performance alone. Changes in self-efficacy expectations predicted changes in cold-pressor tolerance. These findings suggest that self-efficacy expectations can be causal determinants of behavior in an aversive situation. Results of Experiment 2 indicate that self-efficacy was separable from control and that performance was best if both high levels of perceived control and self-efficacy were present. These findings support the notion that self-efficacy expectations can mediate the desirability of providing control, in that those who benefit most from control are those who are most confident they can exercise it.     

Fake feedback on pain tolerance impacts proactive versus reactive control strategies

It is well-known that beliefs about one’s own ability to execute a task influence task performance. Here, we tested the hypothesis that beliefs about a specific self-control capacity, namely pain tolerance, modulate basic cognitive control processes. Participants received fake comparative social feedback that their ability to tolerate painful stimulations was either very poor or outstanding after which they performed an unrelated go/no-go task. Participants receiving low-tolerance feedback, relative to high-tolerance feedback, were less successful at inhibiting their responses and more influenced by previous trial conditions, as indicated by an increased slowdown following errors and more failed inhibitions following go-trials. These observations demonstrate a shift from a more proactive to a more reactive control mode. This study shows that providing feedback about one’s own capacity to control impulsive reactions to painful stimulations directly influences low-level cognitive control dynamics.