Conceived and designed the experiments: JC JK PG KB AC MH. Performed the experiments: PG KB AC MH. Analyzed the data: JC JK PG. Contributed reagents/materials/analysis tools: JK. Wrote the paper: JC JK PG.
The authors have declared that no competing interests exist.
Binaural beats are an auditory phenomenon that has been suggested to alter physiological and cognitive processes including vigilance and brainwave entrainment. Some personality traits measured by the NEO Five Factor Model have been found to alter entrainment using pulsing light stimuli, but as yet no studies have examined if this occurs using steady state presentation of binaural beats for a relatively short presentation of two minutes. This study aimed to examine if binaural beat stimulation altered vigilance or cortical frequencies and if personality traits were involved. Thirty-one participants were played binaural beat stimuli designed to elicit a response at either the Theta (7 Hz) or Beta (16 Hz) frequency bands while undertaking a zero-back vigilance task. EEG was recorded from a high-density electrode cap. No significant differences were found in vigilance or cortical frequency power during binaural beat stimulation compared to a white noise control period. Furthermore, no significant relationships were detected between the above and the Big Five personality traits. This suggests a short presentation of steady state binaural beats are not sufficient to alter vigilance or entrain cortical frequencies at the two bands examined and that certain personality traits were not more susceptible than others.
Externally produced modulation of cortical frequencies can be witnessed via electrophysiological recordings using simple stimuli such as light oscillating at a stable frequency
The Five Factor Model (FFM) of personality
It is currently unknown whether cortical activity is alterable through the FFM using auditory stimuli to generate entrainment. One such method purported to generate cortical entrainment are binaural beats. Binaural beats occur when two sinusoidal waves at slightly differing frequencies are presented separately to each ear
Studies have shown a neurological basis of binaural beats perception which have assisted in identifying subcortical regions associated with processing phase differences between sounds. These have been found to be generated by neurons in the inferior colliculus, auditory cortex
A study examining binaural beat alterations on neuropsychological factors
Based on the above, this study had three main aims:
To examine the effect of binaural beat stimulation on vigilance in a zero-back task,
To determine if cortical frequency entrainment is possible using steady state binaural beats, and
To partially replicate and extend Stough et al.
As Stough et al. found that Beta and Theta frequencies were correlated with personality traits and alterations in vigilance; the current investigation employed these same frequencies for analysis. We hypothesised that, when undergoing stimulation by the Beta frequency carrier tones, participants would show increased vigilance as evidenced by faster reaction times to stimuli and there would be increased Beta and Theta cortical frequency power during binaural beat stimulation. It was also hypothesised that the magnitude of scores in O and C would be positively correlated with perceptual speed and overall cortical power of Theta and Beta frequencies. Finally, we hypothesised that those who scored higher in A would show higher Beta frequency power in the left temporal and central cortical areas. No specific hypotheses were made relating to baseline periods, Neuroticism or Extraversion and entrainment.
Forty-five participants were initially recruited from the general public and from a Melbourne university community. Exclusion criteria for the study consisted of any reported neurological disorder or known hearing damage or loss. Data from 14 participants was removed from the study due to file corruption, missing electrophysiological or behavioural data, (4 females, 3 males), excessive artifact on the EEG (2 females, 3 males) and reports of not being able to perceive the binaural beats (1 female, 1 male). This left a total cohort of 31 participants in the study (20 females, 11 males) with ages ranging from 18 to 60 (
Participants' personality trait scores were measured using the NEO Five Factor Inventory (NEO FFI) questionnaire
Binaural beats at 7 Hz (Theta) and 16 Hz (Beta) were produced using BrainWave Generator software version 3.1.12 (
All binaural beat tones were two minutes in length, with a total of 4 minutes continued presentation while white noise baseline was presented between binaural beat stimulation epochs. Two minutes of constant stimulation per ear was deemed an acceptable timeframe to detect entrainment as studies applying binaural beats for less than two seconds have detected event related potential modulation
The experimental procedure was presented using E-Prime version 2.0.8.22 on a Dell Optiplex 755 computer. A common paradigm used in neuroimaging
EEG data was collected using an Electrical Geodesics Inc. (EGI) EEG acquisition system consisting of a 128-channel Hydrocel Geodesic Sensor Net and a Net Amps 300 high-impedance amplifier. The data were recorded using EGI's acquisition software (i.e., Net Station version 4.2.4) on an Apple Mac Pro computer running OS 10.4. Impedances were kept at less than 50 kΩ as per the manufacturer's instructions (Electrical Geodesics, Inc, Eugene, OR) and examined for electrode bridging. The EEG signal was sampled at 500 Hz.
Note: FL = Front Left, FR = Front Right, CL = Central Left, CR = Central Right, TL = Temporal Left, TR = Temporal Right, PL = Parietal Left, PR = Parietal Right, OL = Occipital Left, OR = Occipital Right.
Participants were seated in a quiet recording room and asked to complete a demographic questionnaire which included items on gender, age and handedness. The participant's head was measured for the appropriate electrode net size and an audiometric test was performed. During the test, participants were played a tone over a 10-second period that alternated from the left to right channel at the 5-second mark. The tone consisted of a 400 Hz sinusoidal waveform and was played at 70 dB SPL.
Following the audiometric test, participants listened to a 30-second example of binaural beat recording at alpha frequency (13 Hz) to minimize any potential interactions on the frequencies of interest. Participants then completed the NEO FFI questionnaire. After completion of the questionnaire the electrode net was place on the participant's head and secured as suggested by the manufacturer's instructions (Electrical Geodesics, Inc, Eugene, OR).
The experiment consisted of eight epochs, with four binaural beat presentations; two of Beta (16 Hz) and Theta (7 Hz) frequencies to left and right ears respectively (See
In order to maintain engagement, test vigilance and control for eye movement artifact, participants were asked to do two consecutive tasks during the recording session. The first was a continuous 0-back task similar to that described in
The recorded EEG was analysed using Brain Vision Analyzer version 2.
Data was converted from Net Station format to Brain Vision Analyzer format via an EEGLAB plug-in. The data were filtered using a low cut of .05 Hz (12 dB per octave) and a high cut of 35 Hz (48 dB per octave) with an averaged electrode reference. All participant data was segmented into blocks relative to the condition presentation time and corrected for EOG using the Gratton, Coles and Donchin
The NEO FFI questionnaire scores were compiled and calculated using a Teleform scanner. NEO FFI scores were divided into low, average and high to examine possible effects of personality trait strength. Categories were created by calculating the means and standard deviations for each personality trait and split according to one standard deviation. A score of low for each of the personality traits were one standard deviation below the mean or less, while a score of high was one standard deviation above the mean or more. Additionally, as the FFM is thought of as a continual construct, NEO FFI scores were also kept as non-categorical, interval data for correlational analysis.
Individual binaural beat stimulation reaction time data was calculated by taking the mean of all target letters that appeared during the binaural beat conditions (for example, left Beta carrier tone, right Beta carrier tone) while mean Beta and Theta reaction time data was calculated from left and right reaction times in the particular frequency range. Baseline reaction times were calculated from target stimuli presented during the two white noise conditions.
In order to increase statistical power, the counterbalanced groups were collapsed into a single collection. Chi square tests revealed no significant difference between the groups for sex (
NEO Group | Range | Total | Percentage % |
Neuro | Low | 9 | 29 |
Average | 16 | 51.6 | |
High | 6 | 19.4 | |
Extra | Low | 4 | 12.9 |
Average | 22 | 71 | |
High | 5 | 16.1 | |
Open | Low | 5 | 16.1 |
Average | 22 | 71 | |
High | 4 | 12.9 | |
Consc | Low | 2 | 6.5 |
Average | 25 | 80.6 | |
High | 4 | 12.9 | |
Agree | Low | 3 | 9.7 |
Average | 24 | 77.4 | |
High | 4 | 12.9 |
N = 31.
Note: Neuro = Neuroticism, Extra = Extraversion, Open = Openness to Experience, Consc = Conscientiousness, Agree = Agreeableness.
To examine if binaural beats affected vigilance, paired samples t-tests were conducted. The tests did not reveal any significant difference between left Beta carrier tone stimulation and right Beta carrier tone stimulation reaction times (
Condition | Reaction Time Mean (S.D.) |
Beta Left Carrier | 645.17 (317.39) |
Beta Right Carrier | 615.22 (133.61) |
Theta Left Carrier | 582.35 (125.23) |
Theta Right Carrier | 619.32 (254.54) |
Beta | 643.52 (279.67) |
Beta Control | 629.47 (297.13) |
Theta | 596.42 (154.98) |
Theta Control | 631.95 (162.15) |
N = 31.
Correlational analysis was employed to determine if there were interrelationships not detected by the t-tests due to the formation of three categorical groups. NEO personality traits and reaction times in the vigilance task were examined on a continuous dimension, however no significant results between the two were found (
Neuro | Extra | Open | Consc | Agree | BetaRT | BContRT | ThetaRT | TContRT | |
Neuro | 1.00 | ||||||||
Extra | −0.54 |
1.00 | |||||||
Open | −0.34 | 0.18 | 1.00 | ||||||
Consc | .46 |
.41 |
0.25 | 1.00 | |||||
Agree | −0.24 | 0.31 | 0.04 | 0.15 | 1.00 | ||||
BetaRT | 0.10 | −0.03 | −0.23 | −0.07 | 0.08 | 1.00 | |||
BContRT | .207 | −.151 | −.238 | −.189 | .022 | .951 |
1.00 | ||
ThetaRT | 0.26 | −0.19 | −0.31 | −0.23 | 0.05 | .39 |
0.45 | 1.00 | |
TContRT | −.144 | .200 | −.124 | .173 | .154 | .516 |
.494 |
.380 |
1.00 |
N = 31.
. Correlation is significant at the 0.01 level (2-tailed).
. Correlation is significant at the 0.05 level (2-tailed).
Note: Neuro = Neuroticism, Extra = Extraversion, Open = Openness to Experience, Consc = Conscientiousness, Agree = Agreeableness, BetaRT = Beta Reaction Time, BContRT = Beta Control Reaction Time, ThetaRT = Theta Reaction Time, TContRT – Theta Control Reaction Time.
To determine if cortical frequencies could be entrained through binaural beat stimulation, a repeated measures ANOVA was employed. No statistical differences were detected between Beta control and stimulation conditions (
Condition | Power Mean (S.D.) |
Beta Control | 15.70 (1.07) |
Beta Experimental | 16.55 (1.24) |
Theta Control | 45.23 (1.71) |
Theta Experimental | 44.52 (2.20) |
N = 31.
To examine the viability of the hypothesis that those who scored high on the O and C personality traits would have increased Beta and Theta cortical power spectral density respectively during binaural beat stimulation, 3(Neo trait score)×2(Condition) ANOVAs were conducted for each of the personality traits and binaural beat frequencies used in the study . The table below (
Power (µV) Mean (S.D.) | |||
Condition | Low | Average | High |
Neuro Beta Control | 13.79 (1.37) | 16.88 (1.38) | 15.43 (3.71) |
Neuro Beta Experimental | 13.44 (1.15) | 18.31 (1.36) | 16.49 (4.99) |
Extra Beta Control | 14.00 (1.79) | 16.06 (1.45) | 15.48 (1.40) |
Extra Beta Experimental | 14.40 (2.77) | 17.36 (2.77) | 14.67 (0.86) |
Open Beta Control | 18.46 (1.27) | 14.35 (1.33) | 19.70 (2.34) |
Open Beta Experimental | 18.51 (1.78) | 15.29 (1.54) | 21.01 (3.20) |
Consc Beta Control | 9.73 (4.80) | 16.72 (1.19) | 12.36 (1.47) |
Consc Beta Experimental | 10.72 (3.58) | 17.58 (1.43) | 12.96 (1.22) |
Agree Beta Control | 15.41 (2.60) | 16.12 (1.32) | 13.4 (1.37) |
Agree Beta Experimental | 14.87 (1.97) | 17.21 (1.56) | 13.83 (1.01) |
N = 31.
The ANOVA found no significant interactions between white noise control and Beta stimulation condition for any of the NEO personality traits (N (
Power (µV) Mean (S.D.) | |||
Condition | Low | Average | High |
Neuro Theta Control | 50.00 (8.25) | 43.62 (9.99) | 42.40 (8.69) |
Neuro Theta Experimental | 50.64 (12.05) | 40.75 (10.26) | 45.40 (10.86) |
Extra Theta Control | 45.82 (4.92) | 44.68 (10.10) | 47.21 (10.86) |
Extra Theta Experimental | 45.43 (9.55) | 44.39 (13.59) | 44.37 (8.79) |
Open Theta Control | 45.68 (9.39) | 45.25 (9.36) | 44.59 (13.12) |
Open Theta Experimental | 45.30 (16.31) | 44.55 (11.76) | 43.40 (12.78) |
Consc Theta Control | 48.37 (10.74) | 43.92 (9.61) | 51.87 (6.90) |
Consc Theta Experimental | 61.30 (2.87) | 43.31 (2.88) | 49.97 (11.55) |
Agree Theta Control | 42.18 (8.81) | 44.53 (9.81) | 51.72 (6.76) |
Agree Theta Experimental | 42.97 (10.02) | 43.66 (12.51) | 50.88 (12.67) |
N = 31.
The statistical analysis conducted found no significant interactions between the NEO traits, score or Theta stimulation condition for N (
Examination of the fourth hypothesis was conducted using a correlational analysis as performed in the study by Stough et al. Correlations for personality traits and cortical spectral density power in both Beta and Theta stimulation conditions in the temporal-central region are shown in
Neuro | Extra | Open | Consc | Agree | |||||||||||||||||
Condition | Beta | BCon | Theta | TCon | Beta | BCon | Theta | TCon | Beta | BCon | Theta | TCon | Beta | BCon | Theta | TCon | Beta | BCon | Theta | TCon | |
Frontal | Left | 0.12 | 0.04 | −0.23 | −0.25 | −0.10 | −0.04 | 0.04 | 0.02 | −0.07 | 0.05 | 0.05 | 0.27 | −0.30 | −0.24 | −0.01 | 0.22 | −0.06 | −0.15 | 0.23 | 0.19 |
Right | 0.21 | 0.17 | −0.24 | −0.27 | −0.23 | −0.15 | 0.12 | 0.04 | −0.17 | 0.02 | 0.05 | 0.10 | −0.31 | −0.22 | 0.07 | 0.26 | −0.10 | −0.24 | 0.20 | 0.15 | |
Central | Left | 0.14 | 0.07 | −0.04 | −0.14 | −0.10 | −0.01 | −0.10 | −0.05 | −0.08 | 0.06 | −0.05 | 0.01 | −0.32 | −0.15 | −0.07 | 0.11 | −0.09 | −0.23 | 0.21 | 0.29 |
Right | 0.18 | 0.16 | −0.05 | −0.28 | −0.18 | −0.13 | −0.03 | −0.01 | −0.18 | 0.00 | −0.02 | −0.01 | −0.30 | −0.21 | 0.03 | 0.26 | −0.15 | −0.24 | 0.16 | 0.11 | |
Temporal | Left | 0.23 | 0.12 | −0.01 | −0.17 | −0.09 | 0.01 | −0.04 | 0.07 | −0.20 | −0.01 | 0.07 | −0.04 | −0.18 | −0.03 | −0.10 | 0.14 | −0.03 | −0.24 | 0.20 | 0.29 |
Right | 0.11 | 0.09 | −0.10 | −0.37 | −0.06 | −0.04 | 0.04 | 0.13 | −0.12 | 0.13 | 0.07 | 0.03 | −0.18 | −0.18 | −0.09 | 0.05 | −0.06 | −0.14 | 0.24 | 0.23 | |
Parietal | Left | 0.25 | 0.19 | −0.20 | −0.26 | −0.22 | −0.19 | 0.16 | 0.32 | −0.21 | −0.02 | 0.06 | 0.08 | −0.24 | −0.18 | 0.08 | 0.27 | −0.13 | −0.32 | 0.16 | 0.24 |
Right | 0.24 | 0.18 | −0.08 | −0.27 | −0.22 | −0.19 | 0.08 | 0.13 | −0.17 | 0.13 | −0.01 | 0.07 | −0.24 | −0.23 | 0.01 | 0.21 | −0.19 | −0.28 | 0.25 | 0.13 | |
Occipital | Left | 0.23 | 0.16 | −0.04 | −0.21 | −0.09 | −0.02 | −0.02 | 0.18 | −0.21 | −0.02 | 0.10 | −0.16 | −0.24 | −0.17 | −0.09 | 0.21 | −0.08 | −0.29 | 0.14 | 0.19 |
Right | 0.10 | 0.05 | −0.13 | −0.37 | −0.05 | 0.01 | 0.04 | 0.16 | −0.13 | 0.09 | 0.05 | −0.08 | −0.20 | −0.20 | −0.09 | 0.07 | −0.05 | −0.12 | 0.24 | 0.22 |
N = 31.
= Significant to 0.05 (Two tailed).
= Significant to 0.01 (Two tailed).
Note: Neuro = Neuroticism, Extra = Extraversion, Open = Openness to Experience, Consc = Conscientiousness, Agree = Agreeableness, BCon = Beta Control, TCon = Theta Control.
As can be seen from the table, no significant correlations were detected between the NEO traits, cortical area or spectral density powers at Control, Beta or Theta frequencies. This did not support the hypothesis that increases in A score would show increases in Beta power in the left temporal-central cortical areas. It also suggests that personality traits as measured by the FFM do not increase or decrease the power of cortical frequencies in either the Beta or Theta range.
This study aimed to determine if binaural beats presented at frequencies corresponding to Beta (16 Hz) and Theta (7 Hz) could alter the cognitive faculty of attention through a vigilance task, if they could be used to entrain the brain to their particular resonance, and if personality traits as measured by the NEO FFI mediated either of the previous variables. Four hypotheses were formulated based on previous findings in order to test the aims; that Beta frequency stimulation would assist in sustaining vigilance, binaural beat stimulation at either Beta or Theta frequencies would increase overall cortical power at those frequencies, that the personality traits of O and C would show increased susceptibility to Beta and Theta beat entrainment respectively and that A would show increased power in Beta frequency in the left temporal-central areas. Statistical analysis revealed that none of the four hypotheses were supported. There were no significant changes in reaction times in either Beta or Theta stimulation or across the NEO traits, which is contrary to the results reported by Lane et al. This may be due to the frequencies in which binaural beats were presented to participants or differences in measurement of vigilance between the two studies. The current study played four minutes (two minutes per ear) of each frequency binaural beat to participants, and used 16 Hz and 7 Hz as the intended entrainment frequencies. By contrast, Lane et al. used a 30-minute task in which participants were presented with binaural beats at 1.5, 4, 16 and 24 Hz, with carrier frequencies cycling from 100 to 300 Hz and combined lower and higher frequencies into pools of Delta/Theta and Beta. Wahbeh et al. used a similar stimulation time for their study yet failed to note any entrainment, which suggests the length of stimulation may not be a factor. Therefore it may be possible the higher vigilance noted in Lane's study was due to the use of both an interaction between the 16 and 24 Hz frequency cycling binaural beats. Secondly, the tasks used to measure vigilance were not identical and may have tapped into difference cognitive domains.
This study used reaction time as an analogue for vigilance, as it was thought that those who are more engaged would be more likely to respond faster to a target than those who are not. Correct versus incorrect measures were recorded, however all included participants successfully identified the target stimuli 100% of the time, suggesting the task may have been too easy. Lane et al. used target hits to non-target false alarm key presses as their measure, which it could be argued may not just reflect vigilance but also the ability to inhibit irrelevant stimuli. Future studies may wish to design a task that adequately measures both in order to elucidate.
Entrainment of Theta frequency as evidenced by increased power spectral density was not observed in this study. Additionally increased Beta power during the stimulation period was also not observed. These results differ from those found by Brady et al., however support those found in the follow up study by Stevens et al. and Wahbeh et al. In contrast, Karino et al. found increased Theta components, however this study used event related presentations to elicit alterations in cortical frequencies.
No direct differences between personality traits and cortical power through binaural beat stimulation, or correlates between the two were detected. This did not support the results of Stough et al., who found that using photic stimulation at Beta and Theta frequencies produced higher overall cortical entrainment in those who scored higher in O and C, while A was associated with increased Theta activity in the left temporal-central area. The obvious answer for these differences would be the unlike methods of attempting entrainment, as photic driving uses pulses of light presented at a steady state in order to generate similar frequency neuronal firing where as in this study steady state binaural beats were used.
While several studies have used binaural beats in conjunction with photic driving into order to generate psychological effects; for a review see
A final consideration is the use of pink noise, overlaid music or sound, to generate some sort of effect. One study
In conclusion, this study aimed to examine if binaural beats were able to alter psychological processes and entrain cortical frequencies. Furthermore it aimed to examine if personality traits modulated entrainment. No statistically significant changes or relationships were detected between binaural beat stimulation at Beta and Theta frequencies and white noise control conditions in any personality trait, the vigilance task or EEG power spectra analysis. These results suggest that relatively short presentation steady state binaural beat stimulation at Beta and Theta frequencies are insufficient to generate entrainment and in turn this lack of entrainment does not seem to be related to personality traits. Additionally it appears that short presentation stimulation of binaural beats is ineffective at altering vigilance.
The authors would like to thank Emily Miller for assisting with formatting.