Common Physical Properties Improve Metaphor Effect Even in the Context of Multiple Examples

Full reference: Criollo, A. B., Díaz-Muelle, S., Ruiz, F. J., & García-Martín, M. B. (2018). Common physical properties improve metaphor effect even in the context of multiple examples. The Psychological Record, 68(4), 513-523. https://doi.org/10.1007/s40732-018-0297-9

Study type: Laboratory experiment with factorial analogue design investigating basic relational learning processes in acceptance and commitment contexts.

Background and objectives

Metaphors are powerful tools in psychological interventions, particularly in acceptance and commitment therapy (ACT). From a relational frame theory (RFT) perspective, metaphors function by facilitating the derivation of relations among different contexts. A previous study by Sierra et al. (2016) demonstrated that including common physical properties among metaphor elements improved their effect in promoting pain tolerance. However, prior research also suggests that presenting multiple examples of a metaphor could enhance generalization of metaphoric effects.

The aim of the present study was to experimentally examine the effects of two factors: (a) the presence or absence of common physical properties in the metaphor content, and (b) the presence or absence of multiple examples of the metaphor. The authors employed a 2×2 factorial design to analyze how these two variables interact in promoting pain tolerance during a cold-presser task. The primary hypothesis was that common physical properties would be the key component enhancing the metaphor effect, independent of whether multiple examples were presented. Additionally, the authors predicted that multiple examples would have no significant effect, given that prior research on relational generalization suggests that multiple examples may be unnecessary when relations among metaphor elements are well-established.

Method

Participants

The study included 84 undergraduate participants (40 women), with ages ranging from 18 to 28 years (M = 20.50, SD = 2.45). Participants were recruited from students across different courses at a Colombian university. Exclusion criteria included history of cardiac problems, high blood pressure, diabetes, epilepsy, chronic pain conditions, or other medical problems that could interfere with the cold-presser task. One participant was excluded because he reached the maximum admissible pain tolerance during prior exposure, resulting in a final analyzed sample of 80 participants.

Experimental design

The study employed a 2×2 factorial design. Independent variables were: (a) presence/absence of common physical properties in the metaphor (Present vs. Absent), and (b) presence/absence of multiple examples of the metaphor (Present vs. Absent). This resulted in four experimental conditions:

1. Metaphors with common physical properties and multiple examples
2. Metaphors with common physical properties without multiple examples
3. Metaphors without common physical properties but with multiple examples
4. Metaphors without common physical properties and without multiple examples

Dependent variables were: (a) pain tolerance (total duration of time the participant kept their hand in the cold water), and (b) pain intensity (score on a 10 cm visual analogue scale). As a control measure, the Acceptance and Action Questionnaire-II (AAQ-II) was used to assess participants' experiential avoidance.

Materials and apparatus

The primary experimental task was a standard cold-presser task. Participants submerged their right hand up to the wrist in a glass container (30×20×20 cm) containing circulating water at a temperature of 4.5 to 5.5°C. A digital thermometer continuously monitored temperature. Two water pumps (26 liters per hour) maintained water circulation. An ice maker was used to maintain constant water temperature. A stopwatch measured the total duration the participant's hand remained in the water (pain tolerance). After each cold-presser task exposure, participants rated pain intensity using a 10 cm visual analogue scale (VAS), where 0 represented "no pain" and 10 represented "maximum imaginable pain."

The metaphor protocols were presented via audio files (~5 minutes duration each) that participants listened to through headphones. Each protocol presented a metaphor relating sensations experienced during the cold-presser task to broader life contexts of the participant, providing a framework for tolerating discomfort. For example, in the swamp metaphor protocol, participants heard detailed narrative descriptions relating the sensation of cold water to the experience of crossing a swamp, emphasizing common physical properties (cold water, sensation of discomfort) shared between the task and the metaphoric context. In the multiple examples protocols, three slightly modified versions of the same metaphor were presented.

Procedure

The procedure was divided into four phases:

Phase 1: Preexperimental measures (10 minutes): After providing informed consent, participants completed an explicit consent form describing procedures and participation conditions. Demographic information was collected. At this point, participants were told that the study aim was to analyze what strategies people with chronic pain use to cope with situations accompanied by significant discomfort. They were informed the goal was to analyze their strategies and that they could consult people suffering from constant chronic pain to help them with their efforts. Additionally, participants completed the AAQ-II during this phase.

Phase 2: Prior cold-presser task (Pretest): Participants were first exposed to the cold-presser task. They received the following instruction: "Insert your right hand into the container and keep it there as long as possible. Remember that you can remove it at any time." The total duration the participant's hand remained in the water (prior pain tolerance) was measured. At the end of exposure, participants provided a VAS rating of the pain intensity experienced.

Phase 3: Metaphor protocols: Participants were randomly assigned to one of the four experimental conditions. Participants sat and listened to the metaphor protocol corresponding to their assigned condition through headphones. Experimenters did not know in advance which protocol each participant would hear (random assignment procedure).

Phase 4: Posterior cold-presser task (Posttest): After listening to the metaphor protocol, participants were again exposed to the cold-presser task using the same instructions as Phase 2. Pain tolerance and pain intensity were measured again. Subsequently, participants were debriefed about the study objectives.

Data analysis

JASP 0.8.5 software was used to conduct Bayesian analyses of variance (Bayesian ANOVAs). Bayesian analyses provide Bayes factors (BF), which quantify the relative evidence favoring the null hypothesis (no effect of the factor) versus the alternative hypothesis (presence of factor effect). A BF > 1 indicates evidence favoring the alternative hypothesis (effect present), whereas a BF < 1 indicates evidence favoring the null hypothesis (no effect). The authors used the following interpretation of Bayes factors: 1–3 = anecdotal evidence; 3–10 = moderate evidence; 10–30 = strong evidence; 30–100 = very strong evidence; > 100 = extreme evidence.

Changes in pain tolerance (posttest score – pretest score) were calculated and used as the primary dependent variable in analyses. Changes in pain intensity across conditions were also compared.

Results

First, it was confirmed that participants in all conditions were randomly assigned equivalently, with no significant differences between groups in prior pain tolerance (AAQ-II scores) or prior pain intensity.

Main analysis of the common physical properties factor: The Bayesian ANOVA analysis showed that the common physical properties factor (present vs. absent) was the only variable significantly associated with an increase in metaphor pain tolerance. In participants assigned to conditions with common physical properties present, a significant increase in pain tolerance from baseline to posttest was observed. Specifically, the Bayes factor for the effect of common physical properties was BF = 7.105, providing moderate to strong evidence that the presence of common physical properties significantly improved the metaphor effect on pain tolerance. This result was independent of whether multiple examples were presented.

Effect of the multiple examples factor: The Bayesian analysis found no significant evidence that the presence of multiple examples had a main effect on pain tolerance or pain intensity. The Bayes factor for the effect of multiple examples was approximately 1, indicating that the data were equally consistent with the hypothesis that there is no effect of multiple examples as with the alternative hypothesis.

Interaction between factors: No significant interaction was found between the common physical properties and multiple examples factors. The model in which only the common physical properties factor explained the data was superior to the complete model including both factors and interaction.

Specific effect on tolerance vs. pain intensity: Subsequent analyses revealed that the effect of common physical properties was specific to pain tolerance (duration of exposure). No significant effects were observed on pain intensity (VAS rating) reported by participants. This suggests that common physical properties improved participants' ability to continue exposing their hand to cold water, but did not necessarily reduce the perceived aversiveness of the experience.

Meta-analysis with Sierra et al. (2016): The authors combined their data with those from the prior study by Sierra et al. (2016), which also examined the effect of common physical properties in metaphors for pain tolerance. The Bayesian meta-analysis of these two studies produced a Bayes factor of BF = 104.54, providing extremely strong and compelling evidence that common physical properties in metaphors significantly improve the metaphor effect on pain tolerance.

Discussion and conclusions

The results of the present study provide strong support for the hypothesis that common physical properties between the metaphoric context and the individual's immediate experience are a key component facilitating the metaphor effect. From a relational frame theory perspective, these findings suggest that the derivation of relations (a central process in RFT) is facilitated when common physical properties are shared among elements of the relational frame established by the metaphor.

A particularly notable finding was that multiple examples had no significant effect. This is consistent with prior research on relational generalization, which suggests that when a relation is clearly established through a specific relation (in this case, a well-structured metaphor with relevant common physical properties), introducing multiple examples may be unnecessary to achieve generalization of the derived relation. This result has important practical implications for therapists using metaphors in ACT: it suggests that investing time in developing a single well-designed metaphor with relevant common physical properties may be more efficient than presenting multiple examples of the same metaphor.

The finding that the effect was specific to pain tolerance (not reported pain intensity) is also theoretically significant. It suggests that the mechanism by which common physical properties function might not be simply through reducing the perceived aversiveness of the experience, but rather through facilitating valued behaviors (in this case, tolerance behavior) in the presence of discomfort. This aligns with the underlying theory of ACT, which emphasizes that the goal is not necessarily to reduce perceived pain or discomfort, but rather to enable people to engage in valued behaviors even in the presence of adverse internal experiences.

Study limitations include its relatively small sample size (N = 80) and use of a convenience sample of undergraduate students. Additionally, the study examined the effect of metaphors in an analogue laboratory task (the cold-presser task), so generalization to clinical contexts of chronic pain would require additional research.

Significance and contribution

This study significantly contributes to understanding the basic mechanisms of metaphorical functioning in psychological contexts. It provides rigorous experimental evidence (confirmed by meta-analysis) that common physical properties between metaphorical elements are a critical component enhancing the effectiveness of metaphors in promoting distress tolerance. The findings have theoretical implications for understanding how analogical reasoning operates in learning and cognition, as well as practical implications for designing interventions that utilize metaphorical resources to improve emotional and behavioral regulation.