Friday, September 23, 2016

The Effect of Binaural Beats on Working Memory Capacity


Background

It has been suggested that cognitive and executive functioning is accompanied by specific brain wave oscillations. Overall, the brain activity within alpha rhythm (7.5 – 12.5 Hz in adults) has been associated with vigilance, inhibitory processes, attention, working memory, perceptual abilities, and information processing speed. Some authors have concluded that oscillations in alpha rhythm indirectly enhance performance in such a way that they filter out irrelevant information and prevent disruptions caused by conflicting stimuli (Klimesch et al., 2007; Rihs et al., 2007; Tuladhar et al., 2007).

One way of ensuring induction of electrical activity in the brain is through binaural beats (BB). BB are subjective auditory sensations caused by presenting tones of slightly different frequencies separately to each ear. As a result, the listener perceives sound with an amplitude that changes with a frequency equal to the difference of frequency in the presented tones, and these two frequencies are integrated at the cortical level into the above-mentioned binaural beat. If the difference in frequencies corresponds to the alpha range (7.5 – 12.5 Hz), then the electrical activity of both hemispheres should merge into one synchronized activity.

Method

In this study, consisting of 50 university/college students, each participant was randomly assigned to either an experimental or control group. The subjects took a computer-administered test consisting of a training period and actual test. During the task, a person is asked to retain randomly presented series of 3 to 7 defined letters. The letters were presented one at a time for 800 milliseconds. After the presentation of each letter, a simple mathematical equation appears on the screen (ex. (2*3) + 7 = ?)

The participant has to assess whether the proposed solution is correct. The mathematical operation is presented to each participant for a specific amount of seconds calculated from his/her individual tempo as measured during his/her individual rehearsal task + 2 SDs. Afterwards, a letter comes up for 800 ms. This process is presented anywhere between 3 and 7 times. Afterwards, a set of letters (a table of all possible letters) is presented to the participant. The participant has to choose the letters that were presented in that trial. The whole task consists of 3 series of each set size. The set sizes range from 3 to 7 letters plus the mathematical operations. In total, 75 letters and 75 mathematical operations are administered to the participant. After completing the AOSPAN task, two scores related to the assessment of working memory capacity were computed. The first score, the Ospan score, has an absolute scoring method, and it represents the sum of all correctly recalled sets of letters in the correct order. The second additional score reflects the total number of errors made solving the mathematical operations.

The baseline measure of the AOSPAN was obtained at the beginning of the experiment. After the first completion of the AOSPAN, participants were randomly assigned to either music with a BB or music without a BB. All participants then listened to a 12 minute long recording of one of the recordings. After those 12 minutes they were asked to retake
the AOSPAN. Both the experimental and control group were exposed to the same procedure with the exception of the inclusion of BB in the music in the experimental condition. Completing the experiment took approximately 50 minutes.

Findings

The results of the study illustrate that BB frequencies corresponding to alpha range of brain activity had a temporary positive effect on the capacity of working memory. Participants undergoing a 12-minute BB stimulation of 9.55 Hz frequency achieved a significant increase in the capacity of their working memory in comparison to a control group, which was not exposed to BB stimulation. Participants exposed to BB just for 12 minutes showed an improvement in their working memory capacity on average by 4.6 points in their score. In terms of the control group, this group either remained unchanged by means of measured performance, or deteriorated by the maximum of one set on average (deterioration of 2.45 points). Thus, the ultimate difference between the experimental and control group represents the difference of 1-2 correctly recalled sets, roughly a range of 7 – 13 %. While the experimental group improved by an average of slightly more than one remembered letter, the control group deteriorated by almost 3 letters in total. The overall mean difference between the two groups was, on average, 4 correctly recalled letters.

Critique

Although this study presents findings that confirm the authors’ hypothesis and further validates previous studies, the sample was composed of young, healthy students. It would be interesting to see results achieved by individuals with memory or other cognitive deficits, older individuals, or people without university/college experience. Additionally, it would be appropriate to extend the time between the solving of the two AOSPAN tasks to reduce the potential effect of fatigue on the test subjects. 

Source

Kraus, J., & Porubanova, M. (2015). The effect of binaural beats on working memory capcity. Studia Psychologica 38 (2), 135-145. 

8 comments:

  1. Very interesting article Hank. I found it quite interesting that just 12 minutes of exposure showed that degree of work improvement among the tested subjects.

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    1. Yeah, I thought this was an interesting study as well, especially given that many I researched didn't necessarily show positive benefits regarding the aspects tested.

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  2. Hank, great way of putting it, "BB are subjective auditory sensations caused by presenting tones of slightly different frequencies separately to each ear." With your understanding of music theory, etc. do you think BB is on to something?

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    1. There are many studies about the benefits music has on an individual, but I'm not sure how much of a relationship BBs have to music. In this study the recordings were sounds like water at the beach and rain, and from what I could gather the BBs were not necessarily an 'obvious' aural feature. It would be quite fascinating to see a study that tested BBs in actual music!

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  3. Hank, great way of putting it, "BB are subjective auditory sensations caused by presenting tones of slightly different frequencies separately to each ear." With your understanding of music theory, etc. do you think BB is on to something?

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    1. I couldn't help but think of the "magical number 7, plus or minus 2" reading we had in our intel theories and applications class. BBs might be a great way to enhance this level of short-term memory.

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  4. Throughout this study Hank, did they mention any persons that were outliers in terms of both the experimental and control groups. Particularly in reference to BB decreasing their memory score in the experimental group; and people that performed beyond average in the control group when it comes to memory? I realize these are very hard and objective outliers potentially, but I'd wonder if they did this on a larger scale of say 100s if it would close the gap significantly between the two groups recalling memory in reference to BB.

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    1. That's a good point, Roland. The study didn't mention any outliers specifically, but some people were screened from the study at the beginning based on their ability to answer mathematical questions. Though relatively simple questions, the few who did not correctly answer enough were not allowed to participate in the study.

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