<p>Short answer: Most literature reviews and meta-analyses on <a href="https://en.wikipedia.org/wiki/Transcranial_direct-current_stimulation" rel="nofollow noreferrer">cognitive enhancement from tDCS</a> have found some promising effects, but it is too early to tell which specific effects will replicate.</p>
<blockquote>
<p>... there is mixed evidence about whether tDCS is useful for cognitive
enhancement in healthy people. Several reviews have found evidence of
small yet significant cognitive improvements.  Other reviews found no
evidence at all ...</p>
</blockquote>
<p>For examples of at least partially favourable reviews, covering many hundreds of studies, see <a href="https://doi.org/10.1016/j.bandc.2014.01.008" rel="nofollow noreferrer">Brunoni &amp; Vanderhasselt (2014)</a>, <a href="https://doi.org/10.1016/j.neuroimage.2013.07.083" rel="nofollow noreferrer">Coffman, Clark &amp; Parasuraman (2014)</a>, <a href="https://doi.org/10.1016/j.brs.2015.06.013" rel="nofollow noreferrer">Price et al (2015)</a>, <a href="https://doi.org/10.1016/j.brs.2016.04.006" rel="nofollow noreferrer">Dedoncker et al (2016)</a> and <a href="https://doi.org/10.1007/s00702-016-1558-x" rel="nofollow noreferrer">Dedoncker et al (2016)</a>, <a href="https://doi.org/10.1016/j.brs.2015.10.006" rel="nofollow noreferrer">Hill, Fitzgerald &amp; Hoy (2016)</a>, <a href="https://doi.org/10.1162/jocn_a_00956" rel="nofollow noreferrer">Mancuso et al (2016)</a>, <a href="https://doi.org/10.1016/j.arr.2015.11.004" rel="nofollow noreferrer">Summers, Kang &amp; Cauraugh (2016)</a>, <a href="https://doi.org/10.1016/j.bandc.2015.11.005" rel="nofollow noreferrer">Hashemirad et al (2016)</a>, <a href="https://www.ncbi.nlm.nih.gov/pubmed/28559804" rel="nofollow noreferrer">Weinberger, Green &amp; Chrysikou (2017)</a>, <a href="https://doi.org/10.1080/13825585.2016.1176986" rel="nofollow noreferrer">Martins et al (2017)</a>, <a href="https://doi.org/10.1007/978-3-319-57379-3_25" rel="nofollow noreferrer">Katsoulaki, Kastrinis &amp; Tsekoura (2017)</a>, <a href="https://doi.org/10.1007/s41465-016-0004-1" rel="nofollow noreferrer">Strobach &amp; Antonenko (2017)</a>, <a href="https://doi.org/10.1007/s41465-016-0006-z" rel="nofollow noreferrer">Schroeder et al (2017)</a>, <a href="http://dx.doi.org/10.5958/0974-360X.2017.00064.6" rel="nofollow noreferrer">Ali, Mansoury, &amp; Samaneh (2017)</a>, <a href="https://doi.org/10.1007/s41465-016-0005-0" rel="nofollow noreferrer">Schroeder &amp; Plewnia (2017)</a>, <a href="https://doi.org/10.1007/s41465-017-0010-y" rel="nofollow noreferrer">Reteig et al (2017)</a>, <a href="https://doi.org/10.1007/978-3-319-57505-6_8" rel="nofollow noreferrer">Sellaro, Nitsche &amp; Colzato (2017)</a>, <a href="https://doi.org/10.3389/fnbeh.2018.00167" rel="nofollow noreferrer">Lucchiari, Sala &amp; Vanutelli (2018)</a>, <a href="https://doi.org/10.1093/geronb/gbz130" rel="nofollow noreferrer">Huo et al (2019)</a>, <a href="https://doi.org/10.1016/j.pnpbp.2019.109814" rel="nofollow noreferrer">Mayer et al (2020)</a>, and <a href="https://en.wikipedia.org/wiki/Neuroenhancement#Transcranial_direct_current_stimulation" rel="nofollow noreferrer">Wikipedia</a>.</p>
<p><strong>Stimulation protocols:</strong></p>
<p>One notable exception is <a href="https://doi.org/10.1016/j.brs.2015.01.400" rel="nofollow noreferrer">Horvath, Forte &amp; Carter (2015)</a>, which found no evidence of cognitive enhancement from tDCS.  Aside from the criticisms that this review has received (see <a href="https://doi.org/10.1016/j.brs.2015.06.001" rel="nofollow noreferrer">here</a>, <a href="https://doi.org/10.1016/j.brs.2015.03.007" rel="nofollow noreferrer">here</a>, and <a href="https://doi.org/10.1016/j.brs.2015.03.008" rel="nofollow noreferrer">here</a>), it did serve to highlight certain issues within this field.  A few more recent reviews concur: eg, <a href="https://doi.org/10.1027/2151-2604/a000396" rel="nofollow noreferrer">Barti et al (2020)</a>, <a href="https://doi.org/10.1016/j.brs.2018.11.008" rel="nofollow noreferrer">Galli et al (2019)</a>.</p>
<p>Reasons for the mixed results found in some reviews may be that many <a href="https://doi.org/10.3389/fnhum.2016.00453" rel="nofollow noreferrer">studies are under-powered</a> (see also <a href="https://doi.org/10.1016/j.cortex.2017.06.021" rel="nofollow noreferrer">Medina &amp; Cason (2017)</a>), or <a href="https://doi.org/10.1007/s41465-017-0007-6" rel="nofollow noreferrer">not long enough</a> (see also <a href="https://doi.org/10.1016/j.neuropsychologia.2017.07.031" rel="nofollow noreferrer">Westwood &amp; Romani (2017)</a>).</p>
<p>More importantly however, tDCS interventions are still in an exploratory phase, and protocols are <a href="https://doi.org/10.3389/fnins.2016.00157" rel="nofollow noreferrer">not yet established and consistent</a> across studies.  There is variability in stimulation location, polarity, intensity, definition, and arrangements.  Thus, studies reporting null results do not necessarily indicate ineffectiveness - rather, they may just be setting boundaries on effective protocols.  Time will tell.</p>
<p>This issue is further exacerbated by the potential specificity of protocol to task and possibly even to individuals.  Although the likelihood of 20 years of research involving numerous experiments by many independent labs being found entirely spurious is fairly low, it is too early to tell which findings will ultimately pan out.  As many of the literature reviews conclude: More replication is desperately needed.</p>

CC BY-SA 4.0
2020-06-01T22:44:32.233Z
2020-08-06T15:58:15.610Z
2020-08-06T15:58:15.610Z
Arnon Weinberg
<p>From the book "The future is faster than you think" by Peter Diamandis, Steven Kotler:</p>

<p>“Consider the nine-dot problem, a classic test of creative problem-solving. Connect nine dots with four lines in ten minutes without lifting your pencil from the paper. Under normal circumstances, fewer than 5 percent of the population can pull this off. In a study run at the University of Sydney in Australia, none of their test subjects did. But then the researchers took a second group of subjects, and used transcranial direct stimulation to artificially mimic many of the changes produced during flow. What happened? Forty percent solved the problem—a record result.”</p>

<p>What is the current scientific consensus on this question?</p>

<p>This appears to be the study mentioned:<br>
Brain stimulation enables the solution of an inherently difficult problem<br>
<a href="https://www.sciencedirect.com/science/article/abs/pii/S0304394012003618" rel="nofollow noreferrer">https://www.sciencedirect.com/science/article/abs/pii/S0304394012003618</a></p>

<p>An APA reference to the study was requested.<br>
Here is one such reference:<br>
Using transcranial direct current stimulation to enhance creative cognition: Interactions between task, polarity, and stimulation site.<br>
<a href="https://psycnet.apa.org/record/2017-24133-001" rel="nofollow noreferrer">https://psycnet.apa.org/record/2017-24133-001</a></p>

<tdcs>
Does Transcranial Direct-Current Stimulation (tDCS) enhance cognitive function?
Alex Ryan
# Does Transcranial Direct-Current Stimulation (tDCS) enhance cognitive function?

(Asked by: username_0 on 2020-04-07)

From the book "The future is faster than you think" by Peter Diamandis, Steven Kotler:

“Consider the nine-dot problem, a classic test of creative problem-solving. Connect nine dots with four lines in ten minutes without lifting your pencil from the paper. Under normal circumstances, fewer than 5 percent of the population can pull this off. In a study run at the University of Sydney in Australia, none of their test subjects did. But then the researchers took a second group of subjects, and used transcranial direct stimulation to artificially mimic many of the changes produced during flow. What happened? Forty percent solved the problem—a record result.”

What is the current scientific consensus on this question?

This appears to be the study mentioned:  
Brain stimulation enables the solution of an inherently difficult problem  
<https://www.sciencedirect.com/science/article/abs/pii/S0304394012003618>

An APA reference to the study was requested.  
Here is one such reference:  
Using transcranial direct current stimulation to enhance creative cognition: Interactions between task, polarity, and stimulation site.  
<https://psycnet.apa.org/record/2017-24133-001>

**Tags:** tdcs


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## 1 answers

### Answer by username_1 on 2020-06-01. Score: 1

Short answer: Most literature reviews and meta-analyses on [cognitive enhancement from tDCS](https://en.wikipedia.org/wiki/Transcranial_direct-current_stimulation) have found some promising effects, but it is too early to tell which specific effects will replicate.

> ... there is mixed evidence about whether tDCS is useful for cognitive
> enhancement in healthy people. Several reviews have found evidence of
> small yet significant cognitive improvements. Other reviews found no
> evidence at all ...

For examples of at least partially favourable reviews, covering many hundreds of studies, see [Brunoni & Vanderhasselt (2014)](https://doi.org/10.1016/j.bandc.2014.01.008), [Coffman, Clark & Parasuraman (2014)](https://doi.org/10.1016/j.neuroimage.2013.07.083), [Price et al (2015)](https://doi.org/10.1016/j.brs.2015.06.013), [Dedoncker et al (2016)](https://doi.org/10.1016/j.brs.2016.04.006) and [Dedoncker et al (2016)](https://doi.org/10.1007/s00702-016-1558-x), [Hill, Fitzgerald & Hoy (2016)](https://doi.org/10.1016/j.brs.2015.10.006), [Mancuso et al (2016)](https://doi.org/10.1162/jocn_a_00956), [Summers, Kang & Cauraugh (2016)](https://doi.org/10.1016/j.arr.2015.11.004), [Hashemirad et al (2016)](https://doi.org/10.1016/j.bandc.2015.11.005), [Weinberger, Green & Chrysikou (2017)](https://www.ncbi.nlm.nih.gov/pubmed/28559804), [Martins et al (2017)](https://doi.org/10.1080/13825585.2016.1176986), [Katsoulaki, Kastrinis & Tsekoura (2017)](https://doi.org/10.1007/978-3-319-57379-3_25), [Strobach & Antonenko (2017)](https://doi.org/10.1007/s41465-016-0004-1), [Schroeder et al (2017)](https://doi.org/10.1007/s41465-016-0006-z), [Ali, Mansoury, & Samaneh (2017)](http://dx.doi.org/10.5958/0974-360X.2017.00064.6), [Schroeder & Plewnia (2017)](https://doi.org/10.1007/s41465-016-0005-0), [Reteig et al (2017)](https://doi.org/10.1007/s41465-017-0010-y), [Sellaro, Nitsche & Colzato (2017)](https://doi.org/10.1007/978-3-319-57505-6_8), [Lucchiari, Sala & Vanutelli (2018)](https://doi.org/10.3389/fnbeh.2018.00167), [Huo et al (2019)](https://doi.org/10.1093/geronb/gbz130), [Mayer et al (2020)](https://doi.org/10.1016/j.pnpbp.2019.109814), and [Wikipedia](https://en.wikipedia.org/wiki/Neuroenhancement#Transcranial_direct_current_stimulation).

**Stimulation protocols:**

One notable exception is [Horvath, Forte & Carter (2015)](https://doi.org/10.1016/j.brs.2015.01.400), which found no evidence of cognitive enhancement from tDCS. Aside from the criticisms that this review has received (see [here](https://doi.org/10.1016/j.brs.2015.06.001), [here](https://doi.org/10.1016/j.brs.2015.03.007), and [here](https://doi.org/10.1016/j.brs.2015.03.008)), it did serve to highlight certain issues within this field. A few more recent reviews concur: eg, [Barti et al (2020)](https://doi.org/10.1027/2151-2604/a000396), [Galli et al (2019)](https://doi.org/10.1016/j.brs.2018.11.008).

Reasons for the mixed results found in some reviews may be that many [studies are under-powered](https://doi.org/10.3389/fnhum.2016.00453) (see also [Medina & Cason (2017)](https://doi.org/10.1016/j.cortex.2017.06.021)), or [not long enough](https://doi.org/10.1007/s41465-017-0007-6) (see also [Westwood & Romani (2017)](https://doi.org/10.1016/j.neuropsychologia.2017.07.031)).

More importantly however, tDCS interventions are still in an exploratory phase, and protocols are [not yet established and consistent](https://doi.org/10.3389/fnins.2016.00157) across studies. There is variability in stimulation location, polarity, intensity, definition, and arrangements. Thus, studies reporting null results do not necessarily indicate ineffectiveness - rather, they may just be setting boundaries on effective protocols. Time will tell.

This issue is further exacerbated by the potential specificity of protocol to task and possibly even to individuals. Although the likelihood of 20 years of research involving numerous experiments by many independent labs being found entirely spurious is fairly low, it is too early to tell which findings will ultimately pan out. As many of the literature reviews conclude: More replication is desperately needed.


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