We Still Don't Know Jack About 'Cognitive Enhancement'

Cognitive neuroscientist Martha Farah offers a warning.

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Oct 25 2015, 3:00pm

Image: Tony Webster/Flickr

Humans in 2015 have a small arsenal of tools available to at least temporarily upgrade our brains via the increasingly popular paradigm of "cognitive enhancement."

This is a different boost than that offered by sketchy as-seen-on-NPR brain training schemes, offering literal, physiological neuro-manipulations via either chemistry or electricity. It's no secret that drugs like Adderall and Ritalin are widely sought after among healthy populations looking for an extra push, while electronic stimulant headsets are seeing a somewhat quieter or at least less fretted-about rise. Do they really work? We mostly don't know, warns cognitive neuroscientist Martha Farah in this week's issue of Science.

However popular, the enhancement effects of stimulant drugs and electrical stimulation headsets remain mostly unproven for otherwise healthy populations, Farah says. In the case of stimulant drugs, the effect offered to healthy users might not be enhanced executive functioning so much as increased motivation and-or improved mood.

"Contemporary attempts at cognitive enhancement involve an array of drugs and devices for modifying brain function," she writes, "such as pills taken by students to help them study, or electrical stimulators focused on prefrontal cortex by electronic game players to sharpen their skills. What is known about current methods of cognitive enhancement? What specifically do they enhance, for whom, and with what risks? We know surprisingly little."

For one thing, studies so far have mostly utilized too-small sample sizes, usually involving less than 50 participants. Complicating things further is the fact that researchers are attempting to explore a highly subjective series of metrics with many means of experimentation and interpretation. Turns out that enhancing a brain has a whole lot to do with the biology and physiology of the particular brain in question.

It seems reasonable to assume that a pill offering improvements to focusing and multitasking abilities in patients with existing deficits would offer improvements to healthy users as well. If an ADHD patient at 90 percent can get to 100 percent with an Adderall dose, then, hey, what's to say a person already at 100 percent can't get to 110 percent?

This intuition may not hold, according to Farah.

"The current evidence suggests a more complex state of affairs," she writes. "The published literature includes substantially different estimates of the effectiveness of prescription stimulants as cognitive enhancers. A recent meta-analysis suggests that the effect is most likely real but small for executive function tests stressing inhibitory control, and probably nonexistent for executive function tests stressing working memory."

"The only large-scale trial we may see is the enormous but uncontrolled and poorly monitored trial of people using these drugs and devices on their own."

And yet the drugs remain highly sought after. A recent report based on interviews with college students found that the benefits were more likely to be motivational or mood-related than strictly cognitive. "Subsequent research confirmed the role of these noncognitive factors for students enhancing with Adderall," Farah continues. "Although they differed minimally from nonusers on attention task performance, they exhibited substantially greater differences in motivation and worse study habits, along with more depressed mood."

It's ultimately pretty hard to separate the notions of motivation and cognitive improvement. A study that finds no gains in executive functioning may not have much to say about motivation's role in improved work quality and quantity. Again, this stuff winds up being subjective and the utility of pharmaceutical stimulants can be expected to vary greatly.

The devices behind transcranial direct current stimulation (TDCS), a more recent trend based on passing weak currents across the brain, are exempted from FDA oversight. Data is scarce, but one attempt at a review study found no improvement. These results have since been attacked as being unnecessarily conservative and even biased, Farah notes.

"At present, there is little to no scientific evidence for or against the effectiveness of these specific systems, nor is there evidence concerning the physiological and psychological effects of regular use over months or years in humans or in animals," she writes.

As the utility of cognitive enhancement methods is largely unknown, so are the risks, particularly when it comes to stimulant drugs. And the companies don't have too much motivation to conduct better studies either—the stimulant use in question is illegal, while TDCS machines can continue to be sold without the backing of evidence.

As a result, Farah concludes, "the only large-scale trial we may see is the enormous but uncontrolled and poorly monitored trial of people using these drugs and devices on their own."