June 17, 2016 Podcast, Smart Drugs 4 Comments

Episode 133

Modern science is proving many traditional herbal medicines to be effective.  In Episode 133, Dr. Andrew Scholey of the Swinburne Centre for Human Psychopharmacology is back to talk about the benefits of Ginseng (see our episode on Bacopa for another example of a traditional herb backed by science).

Mood, Memory, and Mental Fatigue

Numerous studies have confirmed that Ginseng has cognition-enhancing properties, particularly when it comes to memory, mood, and mental fatigue.

A dose of 400mg of Ginseng results in significant improvement in memory throughout the day.  In one study, Dr. Scholey asked participants to learn unique lists of words throughout the day.  The memory-boosting effects of taking Ginseng in the morning lasted well into the afternoon.  Interestingly, the most effective dose was 400mg, not a higher dose of 600mg.

Ginseng also helps you perform better under mental fatigue.  Supplementing with Ginseng protects against low mood and improves cognitive function despite mental fatigue.

And Ginseng has benefits comparable to pharmaceutical heavy-hitters like Modafinil.  In a study comparing the effects of Ginseng and Modafinil, the largest effect size (a measure of how much of an effect a compound has) for Modafinil was 0.77, while the largest for Ginseng was 0.86, meaning that Ginseng had more noticeable effects on certain measures of cognition than Modafinil.  In the case of mental fatigue, Ginseng had double the effect of Modafinil!

Ginseng and Glucose

Everyone knows the brain is an energy hog and takes up about 20-30% of the body’s glucose and oxygen consumption.  You may not know that blood glucose levels are closely linked to cognitive performance.

Ginseng helps to regulate blood glucose levels.  Ginseng seems to help cells involved in cognition take up more glucose and use it more efficiently.  (Ginseng is made up of multiple compounds, so, as you can imagine, there are multiple mechanisms of action.)

American vs. Asian

There are two main types of Ginseng:  American (Panax quinquefolius) and Asian (Panax ginseng).  Asian Ginseng has been studied much more thoroughly and is what is used in traditional Chinese medicine.  The difference between the two types comes down to the levels of different ginsenosides (the active compounds in Ginseng).

American Ginseng has higher levels of Rb1 ginsenosides, while Asian Ginseng has higher levels of Rb2 and RBC ginsenosides.  What does this mean in terms of actual benefits?  American Ginseng boosts working memory (short-term memory), while Asian Ginseng generally improves memory processes — both short-term and long-term memory.  It also improves mood and cognitive performance despite mental fatigue.

Taking Ginseng

It’s important that you find a high-quality extract, since some of the supplements on the market may contain low levels of Ginseng (or even no Ginseng at all!) or contaminated extracts.  A dose of 400mg confers the biggest cognitive benefit.

Dr. Scholey recommends two brands that he’s used in his research:

With these brands, not only are you assured that you’re getting a high-quality extract, but you’re also supporting the companies that actually sponsor research.

There doesn’t appear to be any risk of developing a tolerance to Ginseng, since benefits have only been found after taking acute doses, e.g. immediately after taking Ginseng.  Likewise, there’s no loading period.  You take a pill, get the benefits, and then they wear off.

In terms of timing, there haven’t been any studies on the best time to take it, but for research purposes Dr. Scholey has always administered it in the morning.  Due to the fairly long half of Ginseng (6 hours), taking it too late in the day might disrupt your sleep.

Ginseng is pretty safe, although people with diabetes should discuss with their doctors before starting supplementation.  There have been a few reported cases of Ginseng toxicity, but this is very rare, and seems confined to cases where people took doses tens or hundreds of times the normal amount.

PS:  Ginseng may boost your mood, but so does our weekly newsletter.  Have you joined yet?

Episode Transcript hideshow

— This Week in Neuroscience --

Jesse: Okay, here's one that is a little bit surprising, but apparently there's something pretty good to be said about frequent use of the home computer where the brain is concerned.  In elderly people who may be candidates for oncoming Alzheimer's disease, frequent use of the home computer is negatively correlated with actually getting Alzheimer's.  In other words, a significant correlation was found between infrequent use and brain imaging symptoms commonly seen in early stage Alzheimer's patients.  The volume of the hippocampus is a well-known biomarker for Alzheimer's disease.  When this area starts to shrink, that is a bad sign, you don't want to see that. 

And this study conducted by OHSU, that's Oregon Health Sciences University, around where I come from, they have a Center for Aging and Alzheimer's Disease, and their study found that an additional hour of computer use daily was associated with a .025% larger hippocampal volume.  Which I guess means if you use your computer a whopping 20 hours a dayóI don't think anybody does thatóbut if you did, on average your hippocampus would be one half of a percent larger in size than a non-computer user.  Pretty counterintuitive that such a smaller discrepancy might actually make a difference, but according to this study, it does.  The researchers theorize that those with a smaller hippocampal volume may be less motivated to use their home computer because it requires the use of multiple cognitive domains, including attention, memory, and executive function.  So while it may be a good idea to tell your nine-year-old to get off the computer and go out and play outside, active computer use by the kid's grandparent might be a good sign that's not worth complaining about. 

-- Main Interview --

Dr. Scholey: This was one of the original herbs that was investigated for its cognition-enhancing properties.  I was quite interested because there's a link between blood glucose and cognitive function.  Your listeners are probably aware that the brain is a very greedy organ, so it's about 2% of our human body weight but it's consuming about 20% to 30% of glucose and oxygen.  And in fact, your capacity to regulate blood glucose is very tightly linked to cognitive performance.  There was some evidence showing that ginseng has glucose regulatory properties.  So, we sort of made the link that it possibly could have cognition-enhancing properties.  This was also in keeping to some degree with its traditional use in traditional Chinese medicine, where ginseng is purported to have a kind of anti-fatigue pick-me-up sort of property. 

Jesse: Now, just to clarify: when you say regulatory, is that to say it's bringing levels up if they're too low or suppressing them if they're too high, or a combination of both? 

Dr. Scholey: Yeah, it's actually more related to the former.  So it's the ability to drive the uptake of glucose.  For example, in the standard glucose tolerance test, and individual is given a glucose load and then the levels are recorded in the blood, they go up quite dramatically and then they fall again due largely to the action of insulin.  And it turns out that the rate at which they fall back to baseline is a very good predictor of cognitive function.  In fact, in a lot of disorders like diabetes, this is very tightly linked to glucose regulation, in fact, to the point that some individuals have described Alzheimer's disease as type 3 diabetes because of dysregulation of blood glucose is probably driven partly as well by insulin signaling, including in the brain, where we now know that insulin plays a very central role in some aspects of cognitive function. 

And so, the original studies that we did, this was back in, I think the first publication was in 2001, myself and my then PhD student, David Kennedy, we were at a university in the north of EnglandÖ A series of studies into a number of herbal extracts with purported cognition-enhancing properties, including ginseng.  So in the original study, we were really trying to capture these effects.  So, we did a trial where we used a battery of cognitive tests, the CDR battery.  We used a placebo and three doses of ginseng, a very highly standardized extract, which is very important in these sort of studies.  And then we gave single doses to a cohort of young adults and then tested their cognition an hour, two and half, four, and six hours later.  So, we were taking snapshots of cognitive function following dosing.  Of course, all of these trials I'm describing were done using strict double-blind placebo control conditions.  We found quite clearly an improvement in memory functioning over the course of the day.  It was very striking, actually.  So, these were high functioning young adults, college students, who, say, would come into the lab at 9AM, we tested their memory function during the day, and we found that their memory was still significantly better, say, 3 o'clock in the afternoon.  We just hadn't really extended the testing because we thought any effect would have decayed.  Actually when you look at the pharmacokinetics of the individual components of ginseng, there's a good reason why the effects should endure over that sort of period. 

Jesse: Question on the way that that memory study was done: were they memorizing something early in the day and then just checking back on those memories, or were they being asked to learn new material throughout the day? 

Dr. Scholey: Yeah, good question.  So, the answer is the second.  So, at each time point they underwent a battery of cognitive tests.  So the first thing that happens is they're presented with a list of words, a unique list for each occasion.  And then they do the other cognitive tests, and about 20 or 30 minutes later they're asked to recall the list of words, and there's also some pictures that they had to remember, but there was a different set at each time point.  And then the other thing that we found, which was surprising but one of these things that sometimes makes the whole area of research worthwhile, was that there was a reduction in self-rated alertness.  So, the market for ginseng was billions of dollars worldwide, people were taking it as a kind of pick-me-up, and yet we found that it had a negative effect on alertness actually at a different dose to the dose that improved memory.  But it just shows that these effects can be complex. 

Jesse: Now, you mentioned self-rated alertness.  Does that distinguish from actual alertness?  Were people feeling less alert or were they actually less alert? 

Dr. Scholey: We're talking about sort of mean effects here, so that's important.  This was across the group.  But the typical sort of measures that we use and are used quite widely in psychopharmacology, they're called the Bond-Lader mood scales, which were first developed in the ë70s and have been used in hundreds, probably thousands of drug trials.  The participant is presented with a set of lines.  At the end of each line there's an antonym, a word describing an opposite mood state.  So, maybe alert and drowsy would be one.  There are 16 of them, and they produce 20 mood scale items.  So, alertness, calmness, and contentment.  And so, it was the alertness factor which was reduced.  I should say that was a one-off, so that was not something that we found in subsequent trials.  The memory effect has held up in maybe half-a-dozen trials following the initial one, but the alertness just seemed to be a one-off.  And again, it's one of the quirks of this sort of research, is it's really important to try and replicate the findings as often as possible because you do get these certain effects which can be a little bit fragile from single studies. 

Jesse: What were the number of participants like in these studies? 

Dr. Scholey: So these were typically about 20 to 30 in these early studies.  But these were crossover trials, so each participant came back five times because they were trained on the tasks on one visit, and then subsequent visits they were tested under conditions of placebo and the various doses of ginseng.  And of course the order in which they received each dose was counterbalanced, so it wasn't that everyone got escalating doses.  That was completely counterbalanced, as were the stimuli within each cognitive task. 

Jesse: Could you talk a little bit about dosage sizes and tolerance and frequency of administration, things that people might want to know for their personal use? 

Dr. Scholey: Well, I think probably there are individual differences in people's response.  Typically, we tested 200, 400, and 600 mg, and interestingly the 400 mg dose was the most effective.  And in subsequent studies, we found the 200 or 400 mg more effective than higher doses.  The reasons for that aren't at all clear, but of course we're talking about substances with multiple active ingredients in them, so the pharmacokinetics are very complicated.  But we did find that a lower dose is slightly better.  To make it very clear, these are pharmacologically characterized extracts.  We're not talking about homeopathic type of doses. 

Jesse: Sure.  And as far as that goes, are there different extraction methods or distillation methods that people are going to find used when they're looking for retail ginseng?  If somebody's shopping around and trying to find something for their own medicine cabinet, what should they be looking for? 

Dr. Scholey: I think there are differences in the extracts, and in fact a number of studies have found that some so-called ginseng products on the shelf contain little or no actual ginseng, which is a really big problem in this area.  I'm sure you're aware that regulatory framework in North America and Europe and here in Australia, it differs, and there are different requirements in terms of standardization.  Yeah, in the interest of transparency, I think I should make it clear that a lot of this research has been sponsored by industry partners.  They give us a grant, they don't get involved in our designs.  So, we use an extract called G115, which is an extract from a company who are called Ginsana now, a Swiss company.  That, I know, is very high quality because I've seen a number of documents showing the quality control that they require.  So that's an Asian ginseng called panax ginseng, G115.  And then there's an American ginseng, which is panax quinquefolius.  Now, as I say, these are just the extracts that I've worked with.  There may be other extracts out there that are equally as good, but my own feeling is that it's better to use the extracts that have actually been tested in clinical trials.  The other thing, of course, is that you're also then supporting the companies who actually sponsor research, which is a good thing. 

Jesse: Yeah, that's a great point to make and probably one that we don't make enough.  So for the two main varieties, the American and the Asian ginseng, that's actually a difference in the type of plant, it's not just an extraction method.  Can you give us sort of a compare/contrast breakdown of the differences of those two plant strains? 

Dr. Scholey: Yeah, sure.  So, most of the work is focused on Asian ginseng.  There's a huge market for it partly from its use in traditional Chinese medicine.  It's also a big industry, so there's actually, in 2012 a 325-year-old wild ginseng plant was sold for $1.57 million USD. 

Jesse: Wow. 

Dr. Scholey: Because it's purported to have some kind of special properties.  I don't know about that.  So the active ingredients in ginseng are the ginsenosides.  So, this is a group of aboutówell, there are 11 major ginsenosides and they've got fairly uninspiring names, like Rb1, Rb2, Rg1Ö And there's been quite a lot of research looking at the properties of the individual ginsenosides.  There was a review by Imogen Smith a couple years ago, who was the lead author.  A very compromising review looking at the properties of these individual ginsenosides on neural processes, and there are hundreds of publications, a lot of them on animal models, showing that they have central activation, so they affect the central nervous system.  And the difference between American and Asian ginseng is complements of ginsenosides.  So, in particular, American ginseng has a higher level of the ginsenoside called Rb1, maybe double the amount of Asian ginseng, and Asian ginseng has a higher level of Rb2 and Rc.  So, I'm not an organic chemist, so I can't tell you anything about the structure of these or the structure function relationships, but certainly Rb1, which is an enriched American ginseng, has had a lot of research in the context of its central properties. 

Jesse: And as far as the actual end results that people are going to feel when they take it, why might somebody choose one over the other? 

Dr. Scholey: Overall, the effects of Asian ginseng or panax ginseng is mainly on memory processes, and there are also some effects on mood.  Whereas with American ginseng, the effects appear to be on working memory, so this is the ability to hold information online.  Having said that, the effects of American ginseng or the studies of American ginseng have really been restricted to two studies, both actually from my lab.  So, more work needs to be done there I think, and ideally somebody else will take that up and explore that further. 

Jesse: So for the Asian ginseng, the strongest effects then were on long-term memory vs.  sensory or short-term memory. 

Dr. Scholey: Yeah, so recalling information.  We also found that Asian ginseng has an effect on mental fatigue.  So, it seems to be particularly beneficial under conditions where an individual is hammering their cognitive resources.  So, we have used an instrument that we call the cognitive demand battery, so what happens is that you will sit in front of that computer and you have to do a set of very intense mental operations involving mental arithmetic and vigilance over the course of about an hour.  And what we find under those conditions is that ginseng improves performance and also reduces ratings of mental fatigue.  That's really quite consistent with the idea that ginseng may be helping to regulate blood glucose, at least with Asian ginseng.  And, in fact, what we think may happen is that somehow the ginseng is involved in sensitizing cells so that it kind of drives an increase in levels of glucose.  This was a study that was carried out by another PhD of mine, Jonathan Ray, who found, what was quite paradoxical, is that under these conditions of cognitive demand, performance was better, fatigue was lowered, and yet blood glucose went down.  We think it was because glucose was being, as I say, taken out by active cells involved in cognitive performance. 

Jesse: That's fascinating.  So it sounds like it's getting more efficiently used. 

Dr. Scholey: Exactly.  Although, I think it's also worth mentioning that there are multiple mechanisms, and one of the reasons that myself and other people are looking at herbal extracts in this context is because the attempts to improve cognition using interventions which only affect single mechanisms have been really spectacularly unsuccessful over the years.  It really doesn't fit with what we know about brain function, the idea that you can just go in and really hammer single systems in the brain.  For example, the cholinesterase inhibitors which are used to treat Alzheimer's disease haven't really been what you would call a success story, and probably it's because it really doesn't square with what we know about brain function, which is that it's extremely complicated.  The more we learn about brain function, the more complex it becomes, and we're really just scratching the surface.  But I think that it's unlikely that there's going to be a solution like a kind of double helix of brain function. 

I think the beauty of the brain lies in its complexity.  And so, just seeing that there are certain plants and extracts which have evolved to have complements of properties which nudge many systems in a positive directionÖ And regarding ginseng, we know that some recent studies just from this year have shown that it regulates the cholinergic systems, the system which is really demolished in Alzheimer's disease, but also has effects on glucose regulation, as I said.  And again, another study from this year has shown that it has some cardiovascular benefits.  Because the brain is so richly vascularized, it has a very rich blood supply that systemic improvements in cardiovascular function can also improve brain function. 

Jesse: You said something really interesting there, which was implying that there might've been some coevolution of the plant with humans.  Is there any evidence to that?  The way that some of our food crops have definitely been strongly impacted by generations of human domestication of the plant, do we see that with ginseng?  Or is it essentially a wild plant? 

Dr. Scholey: Yeah, originally a wild plant that has been harvested, I don't know if data exists on the complements of ginsenoside in the ancient plants.  So, I don't know.  But it's a very interesting idea, and of course the idea that there are some questions as to why these plant extracts have evolved these components is a very interesting one and may be to do with commonalities in the human nervous system with other living organisms.  For example, with insects we know that some of these components have evolved to attract insects or to protect against insects.  So, it's possible that some of the roots of these effects lie in that aspect of plant evolution. 

Jesse: Yeah, I know that nicotine is one of the most effective insecticides out there, which is interesting because it can be a strong cognitive booster for humans. 

Dr. Scholey: Exactly.  That's a really excellent example. 

Jesse: Do people build up a tolerance to ginseng if they've been using it for a while?  Is there a point where it sort of has a drop off in its positive effects? 

Dr. Scholey: We haven't really looked at that.  The only study that's looked at that that I've been involved with was a 12-week study where we did find the improvements were restricted to acute doses.  In other words, it does seem to rely on having an effect in the immediate aftermath of a single dose. 

Jesse: Gotcha.  So, no long-term benefits? 

Dr. Scholey: Not that we've seen.  I know there are some ongoing trials in conditions like Alzheimer's, which we'll be examining those, and certainly in animal models there's good evidence that ginseng should benefit conditions like Alzheimer's.  But the translation of animal models into human clinical trials in this field has really been riddled with failure.  So, it's very important for us to see the results in the RCTs. 

Jesse: And I guess that probably also answers my next question, which is, is there ever a loading period where you might take more at the beginning?  But if it seems to be most effective only in acute doses, I'm assuming that a loading period doesn't really factor in. 

Dr. Scholey: Yeah.  And again, this is people who are effectively self-medicating or experimenting themselves with products like ginseng, and I think it's very important that people are aware of the safety profile and look into that.  But also if you're taking any other medications, for example, we always recommend that people discuss it with a physician first. 

Jesse: Based on your experience, are there contraindications or types of people that ginseng might be a bad idea for? 

Dr. Scholey: There have been cases of ginseng toxicity, but it's very rare.  And the cases that I'm aware of have been individuals who actually may have some sort of obsessive-compulsive disorder which gets focused on ginseng, so they're taking huge amountsótens, hundreds of times the amounts we use in our trials.  With its effects on things like glucose regulation, anyone who has any kind of diabetic sort of indications should really discuss it with their GP first. 

Jesse: I know that the brand names for different products are going to vary across the different parts of the world, so what you have in Australia vs.  us in the US, vs.  Europe, they're probably going to be different.  But are there any particular recommendations on trusted brands you want to put out there? 

Dr. Scholey: Yeah, I think the ones that I mentioned beforeÖ And really, again, just to make it absolutely clear, these are the ones that I've worked with and these were sponsored by the industry partners, but I know that they are high quality.  So, G115, which is marketed as Ginsana, and Cereboost, which is manufactured by a very reputable company called Naturex, and I think it's marketed as Cereboost in the US, are the two extracts that I work with and I know that they're high quality.  I think there are a couple of things.  So, again, one of the early studies that we did looked at evoked potentials when people were on ginseng vs.  placebo.  Actually, we did a comparison with gingko, and we found that on ginseng people had a reduced latency of the P300 waveform, which sounds complex, but this is an index of working memory.  What we found was that reduced latency effectively means that people, their working memory would be more efficient when on ginseng.  But more than that, it actually just showed that it was doing something centrally, it was doing something in the brain, which I think is important to show that there is central activation. 

So, there is a couple of other things I might want to mention.  So the first is a study that my PhD student, Chris Neale, was responsible for, where we looked at the effect sizes of all of the studies which looked at ginseng and compared them with effect sizes for a pharmaceutical cognitive enhanceróso, modafinil.  We found that, for modafinil, the largest effect sizes we could findóthis is using a formula which calculates something called Cohen's d, which is just a kind of universal measure of how big an effect isówas .77, whereas for ginseng it was .86.  So, it's certainly comparable with pharmaceutical effect sizes.  And in fact, for mood, this mental fatigue effect that I mentioned earlier, the effect size was nearly double what the effect size was for modafinil, it was 1.4.  So, these are substantial effects. 

But I should also just say that in some of our studies there can be a cost.  So, sometimes when we find benefits of substances like ginseng, say, speed and reaction time, there's a loss on other elements of cognitive function, like an increased error rate, for example.  They tend to be at different doses, so that's important.  But it's worth bearing in mind.  I think if people are going to take these, they might want to think about what could be the most effective dose for them. 

Jesse: Yeah, I think like you mentioned earlier with the brain being so complex, it's difficult to imagine one substance that's going to improve everything across the board.  It seems a lot more realistic to try to find something that's going to help one or a few aspects and just be aware of the tradeoffs. 

Dr. Scholey: That's very true.  I should also just mention that a few years ago there was a Cochrane Review, so this is a very high-level review used very widely in the medical profession to really decide whether something is effective or not.  They set the bar very high, and that review did conclude that, and I'm quoting here, "Ginseng appeared to have some beneficial effects on cognition, behavior, and quality of life."  So, I think of many of the herbal extracts that I've studied in this context, it's one of the most effective as a cognitive enhancer. 

Jesse: And recommendations as far as time of day that people might want to take or avoid it?  It sounds like something that gets cleaned out of your system relatively quickly.  Is it something that might disrupt sleep if somebody took it too late in the day? 

Dr. Scholey: That's possible, and certainly in all of our trials people have taken it in the morning.  And as I say, we were still recording benefits six hours later, so I guess morning might be more effective. 

Jesse: Do we know the exact half-life?  Is that something that's been teased out? 

Dr. Scholey: It is known, but the half-life varies because there are so many different components.  But yeah, so the half-life in some of the ginsenosides is up to I think six hours.  That's for memory, so that may not be accurate, of course.  That's just the half-life, so you still have half the levels in your system after six hours. 

Jesse: I don't think we've actually used the adaptogen yet in this interview, but ginseng would be considered an adaptogen, right? 

Dr. Scholey: Yeah, I mean certainly in traditional Chinese medicine it's seen as an adaptogen, it has a sort of buffering against stress.  From our work, putting people into high levels of mental fatigue and showing that ginseng can protect against the negative mood effects and enhance cognitive function in those conditions, would support that. 

Jesse: So now the fun question: if you were able to do any study you wanted on ginseng to take another run at it with a budget of no object, what would you still want to find out? 

Dr. Scholey: Some of our early studies were looking at EEG.  As I mentioned, at the moment a lot of the studies that we're doing at the Center for Human Psychopharmacology are looking at brain imaging.  So we have fMRI and another methodology called MEG, magnetoencephalography, which looks at changes in the magnetic field of the brain.  I would love to be able to do a study looking at ginseng's effects on brain activation. 

-- Ruthless Listener-Retention Gimmick --

Jesse: So, with water fast week over, I've been back to eating again this week, which has been a nice change.  But since I was deep in ketosis anyway, since my body was already burning fat, I decided I would stay on a very high-fat diet this week and probably for the next couple of months, and so I've been eating a lot of fish.  There's a lot of good, healthy, natural fats in fish, as we talked about before in previous episodes.  And although I certainly understand and I wish that it was not necessary to kill a bunch of animals to eat meat, until we have a nutritionally comparable solution with less ethical difficulties to it, I will probably continue eating animals.  But I definitely feel like, intuitively, there's major gradation between the level of awareness and therefore the level of potential suffering that an animal could have.  I'd much rather eat a roundworm than a monkey because I think a monkey is a lot more aware of its existence.  And I've always thought that fish were probably pretty low on the hierarchy on animal self-awareness, so I've always sort of given myself sort of an ethical-free pass when eating fish, just kind of like, "Ah, c'mon, you know, the fish doesn't really know." 

But I had that rug somewhat pulled out from under me today when I came across a recent study from the University of Oxford that shows unequivocally that at least one species of fish can recognize different human faces, and not just like kinda, sorta squint and recognize them, but really accurately differentiate one human face from another.  And this is weird, this is surprising, you wouldn't think this would be the case.  We talked a lot on previous episodes about specific areas within the human brain.  The main area is something called a fusiform gyrus, which is kind of like a special hardware subcomponent off your brain's motherboard which is specifically for human facial recognition.  It's what allows you to see all the fine gradations in somebody's mood, it's what allows you to not see somebody for 20 years as they age and look overtly different and gain a lot of weight or lose a lot of weight and you still know it's the same person.  So, we've got this special dedicated hardware for facial recognition and we also have a brain that is just, by and large, massive compared to anything else in the animal kingdom. 

So you wouldn't really think that a little fish that does not, needless to say, share an environment with humans, so it has no reason to have evolved any special hardware for recognizing human faces, would necessarily be able to do this.  If you think about it from a fish's perspective, humans have got to be pretty standard-looking.  We've all got these inset areas for our eyes, we've all got foreheads and noses and these gross features that are probably pretty strikingly similar if you're coming from a totally different species.  And yet this little tiny fish called an archer fish, it's called that because it can spit a stream of water to knock insects out of the air, so it's kind of got like a little built-in squirt gun, scientists trained archer fish to get a food reward if they sprayed their water at a particular human face.  This was not a real person's face but an image of a human face on a computer screen.  It got trained that if they sprayed this face, they'll get some food pellets.  And then they would show an array of different faces with the one face that they had been primed to recognize somewhere in the middle of them, and the fish were strikingly accurate at recognizing the face that they had been trained on. 

So they'd show them an array of 44 new faces with sort of the "Where's Waldo? " face hidden among the crowd, and the archer fish would be able to identify and spit their water stream at that one particular face.  The first time they were tested at doing this, they had an average peak performance of 81%, and the next time they got up to 86%.  So this is not a statistical fluke, these fish were definitely pegging their man.  And they were able to do this even when it was just facial features that were distinguishing when they made all the outlines of the heads and the haircuts and things like that strictly identical.  So, the next time should you ever hear someone say that old racist standby, "All so-and-so's look alike," describing some nationality or ethnic group or whatever, feel free to absolutely lay into them.  Because if a little tiny archer fish from a completely different species can distinguish between different human faces, there's absolutely no excuse for any sighted person within our species to not be able to do the same. 

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Written by Hannah Sabih
Hannah believes there's nothing 8 hours of sleep and some kale can't cure (yes, she's from California). She's an avid runner, reader, and traveler, who brings you the latest and greatest in neuroscience via our social media channels.