Are there placebo or nocebo effects in balancing performance?

Horváth et al. Cognitive Research: Principles and Implications https://doi.org/10.1186/s41235-023-00476-z (2023) 8:25 Cognitive Research: Principles and Implications Open Access ORIGINAL ARTICLE Are there placebo or nocebo effects in balancing performance? Áron Horváth1,2,3, Attila Szabo2,4* , Vera Gál2, Csilla Suhaj2, Blanka Aranyosy4 and Ferenc Köteles1,2 Abstract Placebo and nocebo effects could influence the perceived, actual, or both postural stabilities. Therefore, this experiment examined whether postural stability is susceptible to placebo and nocebo effects. Driven by expectations, these cognitions could influence the motor stability of people in physical rehabilitation and those with motion instability. We randomly assigned 78 participants to a placebo, nocebo, or control group. Then, we applied a sham sports cream with positive, negative, or neutral instructions about its impact on balance. Next, we tested postural stability with a modified version of the Modified Clinical Test of Sensory Interaction in Balance, including standard, proprioceptive, visual, and vestibular tests before and after the intervention. Further, we measured expected and perceived performance with visual analog scales and assessed trait anxiety, change in state anxiety, optimism, holistic thinking, persistence, and cooperation with questionnaires. The intervention did not affect actual test performances; similarly, trait and state variables and expectations did not have an impact. Furthermore, the experimental manipulation and trait and state variables did not significantly affect perceived performance. However, the association between expectation and perceived performance was strong (ϱ = 0.627, p < 0.001). These findings suggest that postural stability is not susceptible to placebo and nocebo influences. Still, there is a dissociation between objective and subjective performance, showing that expectations impact perceived but not actual performance, which could fuel motivation in rehabilitation settings. Keywords Balance, Expectations, Placebo, Postural stability, Nocebo Significance statement Postural stability is essential in locomotion, and it is critical in rehabilitation after accidents, sports injuries, or at an older age to avoid the risk of falls. Our research sought to establish whether placebo and nocebo effects, defined in this case as positive and negative suggestions, affect balance, the critical element of postural stability. *Correspondence: Attila Szabo 1 Institute of Psychology, Károli Gáspár University of the Reformed Church in Hungary, Budapest, Hungary 2 Institute of Psychology and Institute of Health Promotion and Sport Sciences, ELTE Eötvös Loránd University, 1117 Budapest, Hungary 3 Doctoral School of Psychology, ELTE Eötvös Loránd University, Budapest, Hungary 4 Institute of Psychology, ELTE Eötvös Loránd University, Budapest, Hungary We examined changes in four conditions (standard, proprioceptive, visual, and vestibular) before and after the respective intervention and presumed that the intervention would affect balancing performance. In this way, we adopted a reverse strategy in which results from applied research would generate research questions and hypotheses for basic research to determine the cognitive mechanisms of the expected effects. The results suggest that these balance tasks are not susceptible to placebo and nocebo effects. However, we used a mild external placebo/nocebo agent, an inert white cream. Still, a dissociation between actual (observed) and perceived (thought) performance was evident in our study. Accordingly, expectations affected the perceived (subjective) but not the actual (objective) performance. Based on (perceived) competence motivation, these findings could have implications for motivation in adherence to interventions © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Horváth et al. Cognitive Research: Principles and Implications (2023) 8:25 aimed at improving postural stability. Indeed, if people believe that their performance is better due to an agent (in our case, an inert cream), they experience ‘positive results.’ These results are the rewards associated with an action (attending therapy). Therefore, they could reinforce the desired behavior and motivate the individual to adhere to physical therapy even though the objective (actual) results appear only later. Are there placebo or nocebo effects in balancing performance? In many cases, believing or expecting something could be a self-fulfilling prophecy that leads to the predicted outcome. In a medical context, this process is called a placebo response if the expectation and the result are positive (i.e., beneficial) (Benedetti, 2009) and a nocebo response if the anticipation and the outcome are negative (i.e., harmful or unpleasant; (Hahn, 1997, 1999). For example, when somebody receives a pharmacologically inert treatment with information about the expected improvements and side effects, they may experience and report the predicted consequences. There are at least three main mechanisms that can drive placebo and nocebo responses: conscious expectations (Kirsch, 1997), classical or social conditioning (Benedetti, 2009), and the so-called meaning response (Moerman, 2002a, 2002b). Placebo and nocebo responses may manifest as peripheral physiological or behavioral changes (de la Fuente-Fernández et al., 2001). Still, in most cases, they dominantly influence the subjective experience (i.e., the perception of the physical condition or performance) without any peripheral or behavioral change (Köteles, 2021; Spiro, 2000). Motor performance is highly susceptible to top-down influences (Bérdi et al., 2011; Horváth et al., 2021; Hurst et al., 2019). On a neural level, it was revealed that placebo and nocebo responses could modify the activity of the opioid, endocannabinoid, and dopamine neurotransmitter systems that regulate pain, fatigue, motivation, and arousal, i.e., factors that can substantially impact motor performance (Beedie et al., 2020). Several empirical studies support this idea; for example, Benedetti et al. (2007) administered morphine in the prep (...truncated)