Table 3.
Studies investigating the role of the experimenter/clinician nonverbal behaviors.
| Study | Design | N (Female) | Sample | Type of provider | Nonverbal behavior | Target outcome | Result |
|---|---|---|---|---|---|---|---|
| Egbert et al (46)* | Between subjects | 97 (63) | Abdominal surgery patients | Clinicians | Enthusiasm and rapport | Narcotic usage, physical and emotional status, postoperative pain intensity | Enthusiastic clinicians induced less postoperative narcotics and a better physical and emotional condition. |
| Gryll and Katahn (63)* | Mixed design | 160 (75) | Dental patients | Clinicians | Warm or neutral behavior of clinicians | Pain intensity, state anxiety | Enthusiastic messages generated lower pain intensity, less anxiety, and higher placebo effects in subjects. |
| Brown et al. (64) | Mixed design | 101 (49) | Healthy participants | Experimenters | Active support (reassuring, encouraging, more understanding, more concern, more eye contact and body gestures), passive supports (small talk, few comments, trying to distract the participant, no eye contact or body gestures) | Pain intensity | Active and passive support of providers generated lower pain intensity compared to alone condition. |
| Kaptchuk et al. (57) | Between subjects | 262 (199) | Patients with IBS | Clinicians | A placebo acupuncture augmented by a warm and friendly manner, active listening and empathy VS a placebo acupuncture alone (limited) and a waiting list | Placebo, global improvement, adequate relief, symptom severity, quality of life | Warm and friendly manner of clinicians generated higher global improvement, adequate relief of symptoms, better quality of life, and lower symptom severity scores in participants. |
| Verheul et al. (65) | Between subjects | 30 (30) | Patients with menstrual pain | Clinicians | Warm and empathic communication (directing gaze and body posture toward participants) VS cold and formal communication (directing gaze and body posture away from participants). | State anxiety, affective state and outcome expectancies | Warm and empathic communication combined with positive expectations led to lower state anxiety. Affect-oriented communication style of providers influenced the positive and negative affects of participants. |
| Modi´c Stanke and Ivanec (66) | Mixed design | 48 (48) | Healthy participants | Experimenters | Physical distance | Pain reports | No significant effects for the physical distance of unfamiliar observers on participants’ pain reports. |
| Bohns and Wiltermuth (67) | Between subjects | 89 (44) | Healthy participants | Experimenters | Personal space and tone of voice | Pain threshold | Preserving the personal space and speaking softly led to higher pain thresholds. |
| Valentini et al. (68) | Within subjects | 27 (12) | Healthy participants | Experimenters | Observation of facial expressions with different emotional content (neutral, pain, and happy) | Pain intensity, placebo effect | Facial expressions (especially happy faces) boosted the placebo analgesia. |
| Ruben and Hall (69) | Within subjects | 95 (55) | Healthy participants | Experimenters | Nonverbally supportive provider (friendly voice, leaning forward, open body posture, eye contact, nodding, and smiling) VS nonverbally unsupportive provider (rarely looking to camera, looking down frequently, folding arms, leaning back, distancing, cold tone of voice). | Judging the intensity of pain in the target (either with a supportive or a unsupportive clinician) | Nonverbally supportive experimenters generated more valid impressions of pain ratings and judges had higher accuracy in their pain assessment when viewing participants tested by supportive clinicians than subjects tested by nonverbally unsupportive clinicians. |
| Ruben et al. (70) | Mixed design | 205 (129) | Healthy participants | Experimenters | High nonverbal support: leaning forward, eye contact, nodding, smiling, gesturing, and using a warm voice tone; low nonverbal support: poor eye contact, looking down frequently, folded arms, leaning back, distancing from participants, and a cold voice tone. | Pain tolerance, pain intensity | Nonverbally supportive experimenters induced higher pain tolerance and a reduction in the expressed pain in participants, compared to less nonverbally supportive clinicians that induced lower pain tolerance in participants. |
| Czerniak et al. (71) | Between subjects | 122 (46) | Healthy participants | Experimenters | Performance status: scenario A: sitting, minimal eye contact, lack of tactile interaction like shaking hands; scenario B: sitting and standing, frequent eye contact, tactile interaction. | Pain threshold and tolerance | Scenario B resulted in an increase in pain threshold compared to scenario A. |
| Howe et al. (44) | Between subjects | 160 (80) | Healthy participants | Experimenters | High warm communication (more eye contact, more smile, less interpersonal distance), VS low warm communication (less eye contact, no smiles, more interpersonal distance). | Placebo and nocebo effects (positive and negative expectations) | Warmer experimenters enhanced the effects of positive expectations about a placebo cream on allergic responses. Less warm experimenters negated the effects of expectations about a placebo cream on allergic response. |
| Van Osch et al. (72) | Between subjects | 293 (293) | Patients with menstrual pain | Clinicians | Positive affect-oriented communication: warm, emphatic; VS negative: cold, formal | Anxiety, mood, expectations, satisfaction | Positive affect-oriented communication reduced anxiety, negative mood, and increased satisfaction, whereas negative communication negated positive expectations and led to higher negative mood and anxiety. |
| He et al. (73) | Between subjects | 89 (67) | Healthy participants | Experimenters |
Communication status: Warm: strong tone, animated facial expressions, frequent eye contact, expressive hand gestures, open posture. Neutral: monotonous voice, neural facial expression, less frequent hand gesture, minimal eye contact. |
Expectation of treatment outcome, motor coordination | Warm experimenters induced higher positive expectations of treatment outcome, more improvement in performance, and better balance and coordination, compared to neutral experimenters that induced lower positive expectations. |
*The procedure of these studies are not well described, but it seems a “social interaction” factor that referred to a warm or neutral behavior of the provider was at play, and also a “pill administration message” factor that reffered to the content of the information about the pill. However, this last factor is confusing and we are not completely sure about what was actually manipulated.