Summary Binaural auditory beats are a perceptual phenomenon that occurs when two tones of slightly different frequency are presented to each ear separately. It has been revealed that binaural beats can, among other things, influence cognition and mental states. The objective of this meta-analysis was to study the effect of binaural beats on memory, attention, anxiety, and pain perception. Twenty-two studies met our inclusion criteria for this meta-analysis. The results, based on 35 effect sizes, showed a mean, significant and constant overall effect level (g = 0.45). The meta regression results indicated that it does not appear necessary to mask binaural beats with white noise or pink noise in terms of efficiency, similar effects are obtained with unmasked binaural beats.
In addition, the results suggest that exposure to binaural beats before, and during the task gives superior results than exposure during the task. Duration of exposure significantly contributed to the model indicating that longer periods are recommended to ensure maximum efficacy. Our meta-analysis adds to the growing evidence that exposure to binaural beats is an effective way to affect cognition, beyond reducing anxiety levels and pain perception without prior training, and that the direction and magnitude of the effect depend on the frequency used, the exposure time and when the exhibition takes place.
Conclusion The objective of this meta-analysis was to provide an overall estimate of the effectiveness of binaural auditory beats on two cognitive functions (memory and attention), as well as on anxiety and analgesia. We intended to answer two questions: (a) what was the overall magnitude of the effectiveness of exposure to binaural beats on the selected outcomes, and (b) were there any attributes of binaural beats that systematically moderate this efficiency?
This meta-analysis provided strong, albeit modest, evidence regarding the effectiveness of binaural beats on memory, attention, anxiety, and analgesia. Based on our results, we can observe that exposure to binaural alpha (3 ES), beta (10 ES), gamma (1 ES) and theta (6 ES) beats affected the performance of memory-demanding tasks, and that this effect depends on the frequency used: positive effect for the alpha, beta and gamma, and negative for theta frequency (except Studies 2 and 27).
Additionally, binaural beats have been shown to be effective in reducing the amount of medication required for preoperative anesthesia. Studies 10 and 21 both applied multi-layered binaural beats, while that Study 25 did not report the frequency used. The efficacy of binaural beats in reducing anxiety levels after exposure to delta / theta was also confirmed in all included studies (k = 5), although Study 29 did not mention frequency used.
Finally, we note that attention was also affected by exposure to binaural sounds. All studies (k = 7), except study number 17, showed positive effects on attention using alpha, beta, and gamma frequencies; Based on our results, we can assume that the reduction in efficacy observed in Study 17 was due to the timing of exposure – only during task – and the masking of the binaural rhythm by music. With respect to these potential moderating variables, the results provided evidence supporting the hypothesis that the timing of exposure plays a critical role in the effectiveness of binaural beats, showing a greater effect when exposure occurs. before, and during the execution of a task. In addition, it appears that the exposure time does not habituate to binaural beats as was initially assumed (Vernon, Peryer, Louch, & Shaw, 2014). On the contrary, our results indicate a positive relationship between the exposure time and the size of the effect, reflecting the fact that not only is it advisable to go through an induction phase to ensure that the frequency desired is driven by when the event or task to be measured begins, but also that the exposure time must be long enough to obtain maximum benefit.
In accordance with this suggestion, it is recommended to carry out an induction phase to ensure that the desired frequency is driven by when the event or task to be measured begins, but also that the exposure time is long enough to get maximum benefit. Recent studies have shown that in order to cause changes in almost all cortical regions, exposure to binaural beats must last 9-10 minutes (Jirakittayakorn & Wongsawat, 2017; Seifi Ala, Ahmadi-Pajouh, & Nasrabadi, 2018).
Regarding the masking of binaural beats, our findings indicated that the unmasked beats were associated with larger effect sizes than the binaural beats masked by music, but no difference was found regarding pink noise or white noise. We can hypothesize that the lower efficiency observed with binaural beats embedded in music might be due to some interference between frequencies present in music and binaural beats, as it has been reported that musical rhythms, even when not strictly periodic, cause body movement (London, 2004; McAuley, 2010; Phillips-Silver & Keller, 2012).
Regarding the frequency of binaural beats, our results indicate that complex frequency binaural beats (i.e., multi-layered) produced the greatest effect. Due to the limited number of studies that have looked at multi-layered binaural beats (k = 3), it is plausible that these results are only valid for surgical procedures and cannot be generalized to a wider range of applications such as improving memory or reducing anxiety. Future studies should address this question and determine whether the reduction in analgesia can be extrapolated to all types of surgical procedures and other areas of cognitive enhancement, and whether multi-layered binaural beats provide a greater effect than single binaural beats. .
Although most studies have found significant differences between binaural pacing and control conditions, it is necessary to identify why some studies could not find such differences. There are some variables that could potentially explain the differences between studies in effectiveness. For example, one of the variables that could play a crucial role in the effectiveness of binaural beats would be the carrier frequency, which would benefit from being studied in future research to determine whether different frequency ranges produce different results. Exposure time, timing of exposure (i.e. before and during the task), and the type of sound that was used to mask the binaural beat are other variables that may moderate the effectiveness of binaural beats that we included in this meta-analysis.
In addition, we should not forget that there is a difference in the perception of binaural beats between males and females (Oster, 1973; Tobias, 1965) and that other inter-individual differences may moderate the results. For example, individual meso-striatal dopamine levels – measured directly by the rate of spontaneous blinking – have been found to determine the degree to which binaural gamma beats affect cognition (Reedijk et al., 2013; Reedijk et al. , 2015). This could potentially be explained by increased sensitivity and a more responsive meso-striatal dopaminergic system that initiates neural processes more efficiently due to a hypodopaminergic state, which can be predicted by the rate of spontaneous blink (Jongkees & Colzato, 2016). This greater sensitivity is common in extroversion differences and involves increased sensory responsiveness, such as lower hearing and sound thresholds (Smith, 1968; Stelmack & Campbell, 1974), and larger potential amplitudes related to early visual events such as N1 (Rammsayer & Stahl, 2004).
In addition, introverts appear to be more sensitive to induced changes in dopaminergic activity, while extroverts exhibit a more efficient compensatory mechanism by which neurotransmission homeostasis is maintained (Rammsayer, Netter & Vogel, 1993). It is therefore essential to determine how these variables affect the efficiency of binaural beats and what is the optimum carrier frequency in order to be able to use the most efficient parameters and thus get the most out of the binaural beats. For the above reasons, the frequency of the binaural beats should be adjusted according to the gender of the listener in order to obtain similar and comparable results taking into account individual differences related to extraversion. One way to reduce these extraversion-related differences might be to use carrier tones at higher frequencies where no significant difference in sensitivity between extroverts and introverts has been observed (Stelmack & Campbell, 1974).
A number of limitations may have influenced the results obtained in the present meta-analysis. For example, with the exception of Study 29, the other included studies had a modest sample size (n <70) which may compromise statistical power and estimates by overestimating the effectiveness of auditory beats. Publication bias is still an issue in the meta-analysis, although statistical testing did not suggest the presence of publication bias. We cannot rule out the possibility that if we had included all insignificant and therefore unpublished studies, the estimate of effect sizes might have been lower. In addition, more studies are needed, as there are currently a very small number of studies that have looked at the practical applications of binaural auditory beats.
Also, despite the importance of carrier frequency, we were unable to include it in our analysis because many of the included studies (33%) did not report such information. It is essential to follow the notification guidelines in order to make progress in this area. Finally, due to the limited number of included studies (k = 22), interaction effects could not be examined and it is possible that the statistical power was not sufficient to perform a meta regression. The associations obtained in meta-regression should be viewed with caution, as they have a lower interpretive capacity than those obtained from randomized comparisons due to their observational and non-causal nature (Thompson & Higgins, 2002).
The results of this meta-analysis are encouraging and should be validated by studies on larger samples to ensure that the observed efficiency can be replicated and applied to other areas such as implicit and episodic memory. Moreover, the results obtained from the meta regressions should also be confirmed in future studies, as they are limited, as the predictors were not based on theory. It is also essential to validate the idea that exposure before, and during the task produces greater efficiency than during the task alone.
Taken together, these results suggest that binaural auditory beats affect memory, anxiety levels, attention, and perceived pain passively and automatically, and that the direction and magnitude of the effect is determined by the frequency of binaural beats, timing and duration of exposure. The mechanisms that explain how binaural stimulation results in psychophysiological changes are still unknown. Therefore, further work in this area is needed and could lead to a better understanding of this phenomenon and to new practical applications in which binaural beats may prove to be more effective.
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Sources: Efficacy of binaural auditory beats in cognition, anxiety, and pain perception: a meta-analysis. Psychological Research 83, 357–372 (2019). https://doi.org/10.1007/s00426-018-1066-8
Miguel Garcia-Argibay, Miguel A. Santed, José M. Reales International authors
Article published in the SVB 2020 available here.
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