Maybe you have heard of binaural beats, a soundwave stimulus that has spread across the internet for having positive effects on mood and cognition. Binaural beats are auditory illusions that occur when presenting two tones with a slight frequency mismatch to each ear separately. Some evidence support that such acoustic stimulation can train the brain signals, altering both, specific brainwaves and connectivity patterns. Other evidence indicates just placebo effects suggesting no better benefits than monoaural beat stimuli. Today, the assumed exceptional effects of binaural beats on human emotion and cognition remain still unclear. Regardless of such discrepancies, what is the scientific evidence of its claimed effects on the human brain?
What are Binaural Beats?
Binaural beats (BB) are auditory illusions that you can experience yourself using stereo headphones. When a constant tone is played at two slightly different frequencies (i.e. tones less than 1000Hz ) in each ear separately, the resonance between the two frequencies is interpreted as a third sound. For example, if a sound with a frequency of 240 Hz is played in your right ear and a frequency of 250 Hz is played in your left ear, the brain creates a binaural beat of 10Hz. The sound of the third rhythm that you perceive actually does not come through the speakers. It is just an illusion created by our brain because it confuses the mixture of two neighboring sounds. In a similar way as the eyes can be tricked into seeing an optical illusion, so can the ears be tricked into hearing a sound that does not really exist.
Indeed, what your brain is actually doing is to activate a compensation process to amend for the frequency difference by adding a third tone somewhere between the two actual tones.
This particular acoustic beat stimulation has long been of interest for its potential applications. Since the early sixties, binaural beats were envisioned as a tool in research and medicine, allowing researchers to investigate the neuronal basis of hearing. Later, Robert Monroe, founder of The Monroe institute (1962), pioneered the used of binaural beats as a therapeutic tool to treat patients with a variety of illnesses. Today, a whole industry patented by Hemi Sync Technology has emerged based on the statement that binaural beats can improve mind wellbeing. An overwhelming variety of binaural beats in video/audio formats are offered as self-affordable tools to influence brainwave activity in such a way that listeners are better able to focus and relax.
What is so Engaging about Binaural Beats?
The use of sounds and rhythms as mood enhancers is not something new. For ages, humans have used music to tune into the “right mood” (e.g. Vivaldi effect). Scientific research on the benefits of music exposure suggest some cognitive improvement after-effects (Mammarella et al., 2007; Tarr et al., 2014) which generalize across cultures and age groups (Schellenberg et al., 2007). Therefore, the potencial of binaural beats as modulators of cognition or mood states makes them an interesting candidate not only for research purposes but for cost-effective clinical applications (e.g. Garcia-Argibay et al., 2019).
Another reason why binaural beats have become so trendy on the internet relates to the seemingly people´s increasing difficulty to focus and be productive in their daily activities. Nowadays, the use of electronic devices such as smartphones has led society to a permanent distraction and being focused can be an ordeal. As a consequence, people are constantly searching for new ways of mentally engaged while improving their cognitive skills. Just by broswing at current digital platforms, you will found out that binaural beats playlists are massively displayed as cognitive (e.g., attention) and mood (e.g., anxiety) enhancers. It is well-known that experiencing these positive effects is highly rewarding, which makes it very attractive to almost anyone.
But let’s breakdown further the mechanisms that justify these brain activity changes induced by BB.
How Binaural Beats Influence Brainwaves?
Brainwaves (delta, theta, alpha, beta and gamma) are neural rhythms oscillating at different frequencies. This brain activity can be measured with an Electroencephalogram (EEG), a technique that places electrodes on the scalp surface to capture the activity of many neurons firing in real-time.
We know from hundreds of studies that different EEG frequency bands are associated with specific cognitive functions, such as selective attention and memory (for a review, see Herrmann et al., 2016).
As brainwaves are much connected to mental states, a main question is whether BB influence EEG signals in a particular way. The main principle is based on the “frequency-following response” (FFR) hypothesis which means that the human brain has the tendency to change its dominant frequency towards the frequency of the external stimulus (Wahbeh, Calabrese, & Zwickey, 2007). To ilustrate this, the dominant frequency of your brainwave activity (e.g. 30Hz) will change to 7 Hz after listening to a 7 Hz binaural beat.
Based on this simple FFR mechanism, BB are assumed to affect brainwaves activity in two possible ways, that is, through entrainment of neural oscillations or by inducing synchronization of brain signals.
- Entrainment: Brainwave entrainment is the brain electrical response to a rhythmic sound or light. When presenting an external stimulus set to a certain frequency for enough amount of time the brain cells start firing at the same frequency as the one presented in the stimulation (Lane et al., 1998; Wahbeh et al., 2007). This is indeed the frequency-following response and reflects the neuroplasticity legacy of the human brain (Coffey et al., 2019). The extent to which this response indicates that someone can increase focus on task performance simply by listening to a beta wave binaural beat or sleep better after listening to a delta wave binaural beat continues to be debated.
- Synchronization: refers to the coordination of brainwaves in time and across different brain regions. When listenting to BB, both left and right hemispheres cooperate to extract the third tone out of the two, thus leading the whole brain into a synchronization (Solcà et al., 2016). Such cooperation between the right and left hemispheres creates homeostasis in the central nervous system that is essential for learning, produce more organized speech, thinking intelligently, and become proficient in whatever it is we are engaged in (Benet & Benet, 2008; Cook, 2002; Hoptman & Davidson, 1994).
Since the publication of “Auditory Beats in the Brain” by Dr. Gerald Oster (Scientific American, 1978), the use of binaural beats to enhance mood and cognition based on brainwaves modulation has been a source of speculation and large debate in the scientific community (Huang and Charyton, 2008; Vernon, 2009). A main question is whether changes in brainwave oscillatory activity necessarily leads to a change in cognition or emotional estate. If so, how can we be sure that showed effects did not come up due to other reasons such as placebo, autosuggestion, or just by chance?
Lets get to know better what evidence exist about claimed benefits of binaural beats.
Scientific Evidence Review
Much scientific research has been conducted on brain responses to binaural beat stimuli. A main focus of interest refers to whether binaural-beat training is effective to affect cognition and mood. According to a recent analysis of more than 30 studies modest effects on attention, memory, anxiety, sleep and pain perception are reported after BB stimulation. Although interesting, the results are controversial and still, today continue to be debated. Several factors like beat and tone frequency, exposure duration, and recording procedures interfere with the validation of the procedures, as these are key factors that affect brain responses. Moreover, the differences in these factors prevent clear comparisons between studies.
Let’s get to know a little better the spotlight of current evidence supporting brain beats effects in cognition.
Prolonged exposure to binaural-beats may affect verbal memory recall. Particularly, alpha, beta, gamma and theta BB exposure may affect the performance in memory recall tasks (Garcia-Argibay, Santed & Reales, 2017). However, the direction of the improvement depends on the frequency used. For instance, stimulation at 7 Hz during 30-min, decreases verbal memory recall (Wahbeh et al., 2007). In contrast, a 15 min binaural-beat stimulation at 5Hz twice per day for 15 days, results in a significant increase memory recall (Ortiz et al., 2008).
In order better clarify the role of binaural beats on such memory effects, direct changes in neural frequencies need to be investigated further.
BB stimulation at alpha range frequencies has a temporary positive effect on the capacity of working memory. In some studies it is concluded that binaural impulses improve working memory performance by increasing theta band (4-8 Hz) activity (Kraus & Porubanova, 2015; Kalyan & Kaushal, 2016). Further, listening to 15Hz binaural beats during performance of a visuospatial working memory task have been also shown to increase the response accuracy (Beauchene et al. (2016).
Findings reveal some effectiveness of binaural beats in reducing the amount of intraoperative anesthesia as well as in reducing patients´ perceived pain (Lewis et al. 2004; Roshani et al., 2019; Zampi, 2016). However, these studies do not specify which EEG brainwave frequencies should be stimulated to affect perception of pain which may limit the use of BB protocol for clinical purposes.
The effects of BB on reducing anxiety have been the subject of considerable scientific interest. In two controlled study in a sample of 100 people that were about to undergo surgery showed that pre-operative anxiety was significantly reduced after BB stimulation compared to no acoustic stimulation at all (Padmanabhan, Hildreth, Laws, 2005). Similar results were recently reported in a sample of 60 patients presenting to the surgical unit (Roshani et al., 2019). In non-surgical popultation (e.g. anxiety trait), research is not consistent enought. There are some studies supporting benefits on anxiety reduction after delta/theta binaural-beats exposure (e.g. Wahbeh et al., 2007) while in other studies appear unclear (e.g. Pluck & López-Avila, 2019).
Scientific findings on positive effects on attention after binaural-beat training appear pretty consistent. However, research needs to clarify the specific brainwaves affected by BB during task performance. For instance, some studies support improvements on the efficiency of attention allocation with BB entrainment when affecting gamma-band frequency (Colzato et al., 2017; Ross & Lopez, 2020). In contrast, other studies found attention improvement effects after affecting alpha and beta frequencies ( Park et al., 2018)
Binaural beats have been tested to treat Attention Deficit Hyperactivity Disorder (ADHD), showing no conclusive results (Kenel et al., 2010). While more research is needed, some potentially promising outcomes have been shown. A moderate effect on a sample of ADHD participants (14-62 age range) has been recently reported in a study led by the California State University Stanislaus (Lopez, 2019).
Most of available evidence is not consistent enough. A recent study conducted by researchers of the Laboratory for Brain, Music and Sound Research in Montreal (BRAMS; Orozco-Perez et al., 2020), fail to prove a mood enhancement after binaural beats entrainment, which contradicts previous findings supporting an effect on negative mood decrease (Chaieb et al, 2015; Jirakittayakorn & Wongsawat, 2017; Lane et al., 1998; Wahbeh, Calabrese & Zwickey, 2007). A possible explanation for these discrepancies can be found in the different listening times reported carried out studies. If the duration is too long, negative effects may arise, for example, increased fatigue, tiredness, while an adequate duration could explain the opposite effect. The problem is that for each person, the optimal exposure to BB may not be the same, which in part explains why a consensus has yet not been provided.
Insights of BB influence on sleep quality appear scarce. Recent research provides evidence of modulatory effects of BB on the quality and efficiency of different sleep phases (e.g. slow-wave sleep, REM sleep). Compared to a control group, reported results suggested relative improvements in a group of participants receiving 3Hz binaural beat stimulation (Jirakittayakorn & Wongsawat 2018). Since binaural beat stimulus corresponded to a single night, evidence of long-term exposure and habituation should be further investigated (e.g. Lee et al., 2019).
To know further about cited evidence, a recap of some relevant studies, the used methodology, and the reported BB effects (1998-2020) is depicted in the next table:
|Study||Participants||Tested Effects||Time Exposure (min)||Trained EEG frequency||N||Task||Control group||Exposure interval||Outcomes|
|Lane et al. (1998)||Healthy adults||Memory/Mood||30||Beta||29||Recognition task (hit)||Theta BB||During||> Exectution improvements, less consusion/fatigue|
|Padmanabhan et al. (2005)||Surgery patients||Pre-operative anxiety||30||NR||70||Anxiety levels||Blank tape||Before||Useful to produce anxiolysis|
|Lewis et al. (2004)||Healthy adults||Analgesia||130||NR||30||Amount of anesthesia||Blank tape||During||Reduction of analgesia dose intake|
|Wahbeh et al. (2007)||Healthy adults||Memory||30||Theta, Delta||4||Verbal working memory||Blank tape||During||No relative improvement|
|Wahbeh et al. (2007)||Healthy adults||Trait Anxiety||30||Delta||8||Quality of life & anxiety||Baseline||Before||> Relative Improvement|
|Ortiz et al. (2008)||Healthy adults||Memory||15||Theta, Beta||18||Verbal working memory||Baseline||During||> Enhancement|
|Dabu-Bondoc et al. (2010)||Surgery patients||Analgesia||30||Complex||60||Amount of anesthesia||WN||Before and during||Positive effects on pain reduction|
|Kennel et al. (2010)||ADHD children||Attention||20||Beta||20||Attention task||Music||During||No improvement|
|Lavallee, Koren & Persinger, 2011||Novice vs Experienced meditators||Deep meditation||40||Delta, Theta, Alpha, Gamma||8||Frequency band entrainment||Baseline/ Pink noise||During||> Enhancement with limitations|
|Crespo et al. (2013)||Healthy adults||Attention||20||Beta||60||Attention task||Music||Before||No improvement|
|McConnel et al. (2014)||Healthy adults||Relaxation||20||Theta||21||Heart rate variability||Pink noise||Before||Contradictory effects|
|Kraus and Porubanová (2015)||Healthy adults||Memory||12||Alpha||20||Working memory||Sea sounds||Before||> Enhancement|
|Reedijk et al. (2015)||Healthy adults||Attention||3||Gamma, Alpha||24||Attention task||Baseline||Before and during||> Enhancement but with limitations|
|Hommel et al. (2016)||Healthy adults||Attention/cognitive flexibility||40||Gamma||40||Attention task||WN||Before and during||>Enhancement|
|Beauchene et al. (2016)||Healthy adults||Memory||5||Beta, Theta & Alpha||28||Verbal working memory||Blank tape||During||>Enhacement|
|Solcà et al. (2016)||Healthy adults||Attention||4||Alpha||18||Dichotic digit task||Baseline||During||No relative improvement|
|Colzato et al. (2017)||Healthy adults||Memory||10||Gamma||40||Visual working memory||Constant tone||Before and during||> Enhancement episodic memory|
|Isik et al. (2017)||Healthy adults||Pre-operative anxiety||10||Theta||60||Anxiety levels||Blank tape||Before||Useful with limitations|
|Beauchene et al. (2017)||Healthy adults||Memory||5||Beta, Theta & Alpha||34||Visuospatial memory||Blank tape||During||> Enhacement|
|Colzato et al. (2017)||Healthy adults||Attention||3||Gamma||36||Attention task||Constant tone||Before and during||> Attentional focusing|
|Garcia-Argibay et al. (2017)||Healthy adults||Memory||17||Beta, Theta & Beta||32||Free recall task / Recognition task||WN||Before and during||Contradictory|
|López-Caballero & Escera (2017)||Healthy adults||Emotional Arousal||60||Theta, Alpha, Beta, Gamma||14||Heart rate and skin galvanic response||Pink noise||During||No changes in arousal autonomic measures|
|Orozco-Perez et al., (2020)||Healthy adults||Attention/ Mood||16||Theta, Gamma||16||Steady-State responses/Visual analogue scales||Monaural beats/Baseline||Before/ After||No relative improvement|
|Ross & Lopez (2020)||Healthy adults||Attention||80||Gamma||29||Attentional blink task||Beta BB||Between sessions||> Relative improvement on task performance|
Acronymes: NR not reported, WN white noise, BB binaural beat, FA false alarms
To be considered
Although the results of published studies are promising, it is important to note that they are not conclusive. The main suggestion is that binaural beats might have some positive effect on the brain correlating with a specific cognitive or mood state.
Part of the study outcomes inconsistencies are due to differences in the adopted methodological approaches.
Besides, several questions need to be answered first in order to demonstrate a long-term therapeutic efficacy of BBs and, above all, to ensure that these sounds actually influence brainwaves in a consistent and accurate way.
|To be investigated further|
|(1) Comparison of BB brainwaves entrainment mechanisms with other methods like Neurofeedback and non-invasive brain stimulation (e.g. tES, TMS) and with different types of sham controls.|
|(2) Placebo effects|
|(3) Influence of BB on the background brainwave activity (e.g. Auditory Steady-State Response).|
|(4) Definition of optimal parameters (EEG frequency, exposure duration, type of task or brain state, etc.) for enhancement or treatment of specific brain functions or pathologies.|
|(5) Validation of current findings in larger sample-size studies|
To beat or not to beat?
In the meantime, you might be wondering if binaural sounds are safe to use. As explained, binaural beats are just audio frequencies that interact with brainwaves. For example, they can be useful as a method of relaxation or meditation, such as other types of sound waves for that matter. So for most people, BBs are safe.
But, in case you belong to any of the following groups, it is advisable to consult a doctor before trying binaural beats:
- People with a histoy of seizures or epilepsy – the change in brainwaves can activate seizures events.
- Heart disease patients or who have a pacemaker– heart rhythm can be influenced by brainwaves changes.
- People taking drugs or with psyquiatric disorders
- Children- not recommended for neurodevelopment inmaturiy reasons
- Pregnant women
Taken together, current evidence suggests that binaural beats may affect cognition, mood and perceived pain in a passive way. They also indicate that the direction and the magnitude of the effect could be determined by the BB specific frequency, moment and duration of exposure.
The brain mechanisms of this acoustic stimulation and how it translates into psychophysiological changes are not well-defined yet. Hence, further investigation is needed to confirm the potential application areas where binaural beats may exhibit further efficacy.
Have you had any experience with binaural beats? Let me know in the comments section.
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