Spike activity 14-07-2015

Quick links from the past week in mind and brain news:

Trends and fashions in the science of neurotransmitters. Neuroskeptic looks at this seasons hottest brain chemicals.

MIT Tech Reviews has an interesting piece on the new wave of normal hearing enhancement hearing aids.

Sorry Paleo diet aficionados, carbs were probably essentially to our evolving brains in early human history. Good piece in The New York Times.

National Geographic has a piece on how some isolated tribes in the Amazon are initiating contact and how it’s causing a rethink of existing policies.

Brain imaging research is often wrong. This researcher wants to change that. Great interview with Russ Poldrack in Vox.

Neurocritic asks: Will machine learning create new diagnostic categories, or just refine the ones we already have?

The Obscure Neuroscience Problem That’s Plaguing VR. Interesting Wired piece on the physiological challenges of virtual reality.

The Atlantic has thought-provoking article on ‘Learning Empathy From the Dead’ – the effects of corpse dissection on medical students’ empathy.

The amygdala is NOT the brain’s fear center. Joseph LeDoux sings it from his new blog I Got a Mind to Tell You.

Good edition of ABC Radio’s Philosopher’s Zone on dreaming.

Postmortemgirl has a great guide to postmortem brain studies in mental health.

Digital tech, the BMJ, and The Baroness

CC Licensed Photo by Flickr user World Bank Photo Collection. Click for source.The British Medical Journal just published an editorial by me, Dorothy Bishop and Andrew Przybylski about the debate over digital technology and young people that focuses on Susan Greenfield’s mostly, it has to be said, unhelpful contributions.

Through appearances, interviews, and a recent book Susan Greenfield, a senior research fellow at Lincoln College, Oxford, has promoted the idea that internet use and computer games can have harmful effects on the brain, emotions, and behaviour, and she draws a parallel between the effects of digital technology and climate change. Despite repeated calls for her to publish these claims in the peer reviewed scientific literature, where clinical researchers can check how well they are supported by evidence, this has not happened, and the claims have largely been aired in the media. As scientists working in mental health, developmental neuropsychology, and the psychological impact of digital technology, we are concerned that Greenfield’s claims are not based on a fair scientific appraisal of the evidence, often confuse correlation for causation, give undue weight to anecdote and poor quality studies, and are misleading to parents and the public at large.

It continues from there.

I was also on Channel 4 News last night, debating The Baroness, and they seem to put some of their programme online as YouTube clips so if our section turns up online, I’ll post it here.

UPDATE: It disappeared on the Channel 4 site but it seems to be archived on Yahoo of all places. Either way you can now view it here.

Greenfield was lovely, as on the previous occasion we met. Actually, she didn’t remember meeting me before, despite the fact she specifically invited me to debate her on this topic at a All-Party Parliamentary Group in 2010, but I suspect what was a markedly atypical experience for me, was probably pretty humdrum for her.

Either way, she trotted out the same justifications. ‘I’ve written a book.’ ‘It contains 250 references.’ ‘The internet could trigger autistic-like traits.’

Dorothy Bishop has had a look at those 250 references and they’re not very convincing but actually our main message is shared by pretty much everyone who’s debated Greenfield over the years: describe your claims in a scientific paper and submitted them to a peer-reviewed journal so they can be examined through the rigour of the scientific process.

Oddly, Greenfield continues to publish peer-reviewed papers from her work on the neuroscience of Alzheimer’s disease but refuses to do so for her claims on digital technology and the brain.

It’s a remarkable case of scientific double standards and the public really deserves better.

Link to ‘The debate over digital technology and young people’ in the BMJ.

So the video of my debate with Greenfield is up online but it seems like you can’t embed it so you’ll have to follow this link to watch it.

Watching it back, one thing really stands out: Greenfield’s bizarre and continuing insistence that using the internet could ‘trigger’ autistic-like symptoms in young people, saying that most kids with autism are not diagnosed until age five and many use computers before.

This shows a fundamental misunderstanding of what autism is, and how diagnosis is done. Autism is diagnosed both on presentation (how you are at the time) and history (how you have been throughout your life) and to get a diagnosis of autism spectrum disorder you have to demonstrate both. So by definition, being ‘turned autistic’ at age 4 or 5 doesn’t even make sense diagnostically, let alone scientifically, as we know autism is a life-long neurodevelopmental condition.

Intuitions about free will and the brain

Libet’s classifc experiment on the neuroscience of free will tells us more about our intuition than about our actual freedom

It is perhaps the most famous experiment in neuroscience. In 1983, Benjamin Libet sparked controversy with his demonstration that our sense of free will may be an illusion, a controversy that has only increased ever since.

Libet’s experiment has three vital components: a choice, a measure of brain activity and a clock.

The choice is to move either your left or right arm. In the original version of the experiment this is by flicking your wrist; in some versions of the experiment it is to raise your left or right finger. Libet’s participants were instructed to “let the urge [to move] appear on its own at any time without any pre-planning or concentration on when to act”. The precise time at which you move is recorded from the muscles of your arm.

The measure of brain activity is taken via electrodes on the scalp. When the electrodes are placed over the motor cortex (roughly along the middle of the head), a different electrical signal appears between right and left as you plan and execute a movement on either the left or right.

The clock is specially designed to allow participants to discern sub-second changes. This clock has a single dot, which travels around the face of the clock every 2.56 seconds. This means that by reporting position you are reporting time. If we assume you can report position accurately to 5 degree angle, that means you can use this clock to report time to within 36 milliseconds – that’s 36 thousandths of a second.

Putting these ingredients together, Libet took one extra vital measurement. He asked participants to report, using the clock, exactly the point when they made the decision to move.

Physiologists had known for decades that a fraction of a second before you actually move the electrical signals in your brain change. So it was in Libet’s experiment, a fraction of a second before participants moved, a reliable change could be recorded using the electrodes. But the explosive result was when participants reported deciding to move. This occurred in between the electric change in the brain and the actual movement. This means, as sure as cause follows effect, that the feeling of deciding couldn’t be a timely report of whatever was causing the movement. The electrode recording showed that the decision had – in some sense – already been made before the participants were aware of having taken action. The brain signals were changing before the subjective experience of taking a decision occurred.

Had participants’ brains already made the decision? Was the feeling of choosing just an illusion? Controversy has raged ever since. There is far more to the discussion about neuroscience and free will than this one experiment, but its simplicity has allowed it to capture the imagination of many who think our status as biological creatures limits our free will, as well as those who argue that free will survives the challenge of our minds being firmly grounded in our biological brains.

Part of the appeal of the Libet experiment is due to two pervasive intuitions we have about the mind. Without these intuitions the experiment doesn’t seem so surprising.

The first intuition is the feeling that our minds are a separate thing from our physical selves – a natural dualism that pushes us to believe that the mind is a pure, abstract place, free from biological constraints. A moment’s thought about the last time you were grumpy because you were hungry shatters this illusion, but I’d argue that it is still a persistent theme in our thinking. Why else would we be the least surprised that it is possible to find neural correlates of mental events? If we really believed, in our heart of hearts, that the mind is based in the brain, then we would know that every mental change must have a corresponding change in the brain.

The second pervasive intuition, which makes us surprised by the Libet experiment, is the belief that we know our own minds. This is the belief that our subjective experience of making decisions is an accurate report of how that decision is made. The mind is like a machine – as long as it runs right, we are happily ignorant of how it works. It is only when mistakes or contradictions arise that we’re drawn to look under the hood: Why didn’t I notice that exit? How could I forget that person’s name? Why does the feeling of deciding come after the brain changes associated with decision making?

There’s no reason to think that we are reliable reporters of every aspect of our minds. Psychology, in fact, gives us lots of examples of where we often get things wrong. The feeling of deciding in the Libet experiment may be a complete illusion – maybe the real decision really is made ‘by our brains’ somehow – or maybe it is just that the feeling of deciding is delayed from our actual deciding. Just because we erroneously report the timing of the decision, doesn’t mean we weren’t intimately involved in it, in whatever meaningful sense that can be.

More is written about the Libet experiment every year. It has spawned an academic industry investigating the neuroscience of free will. There are many criticisms and rebuttals, with debate raging about how and if the experiment is relevant to the freedom of our everyday choices. Even supporters of Libet have to admit that the situation used in the experiment may be too artificial to be a direct model of real everyday choices. But the basic experiment continues to inspire discussion and provoke new thoughts about the way our freedom is rooted in our brains. And that, I’d argue, is due to the way it helps us confront our intuitions about the way the mind works, and to see that things are more complex than we instinctively imagine.

This is my latest column for BBC Future. The original is here. You may also enjoy this recent post on mindhacks.com Critical strategies for free will experiments

Critical strategies for free will experiments

waveBenjamin Libet’s experiment on the neuroscience of free will needs little introduction. (If you do need an introduction, it’s the topic of my latest column for BBC Future). His reports that the subjective feeling of making a choice only come after the brain signals indicating a choice has been made are famous, and have produced controversy ever since they were published in the 1980s.

For a simple experiment, Libet’s paradigm admits to a large number of interpretations, which I think is an important lesson. Here are some common, and less common, critiques of the experiment:

The Disconnect Criticism

The choice required from Libet’s participants was trivial and inconsequential. Moreover, they were specifically told to make the choice without any reason (“let the urge [to move] appear on its own at any time without any pre-planning or concentration on when to act”). A common criticism is that this kind of choice has little to tell us about everyday choices which are considered, consequential or which are actively trying to involve ourselves in.

The timing criticism(s)

Dennett discusses how the original interpretation of the experiment assumes that the choosing self exists at a particular point and at particular time – so, for example, maybe in some central ‘Cartesian Theatre’ in which information from motor cortex and visual cortex come together, but crucially, does not have direct report of (say) the information about timing gathered by the visual cortex. Even in a freely choosing self, there will be timing delays as information on the clock time is ‘connected up’ with information on when the movement decision was made. These, Dennett argues, could produce the result Libet saw without indicating a fatal compromise for free choice.

My spin on this is that the Libet result shows, minimally, that we don’t accurately know the timing of our decisions, but inaccurate judgements about the timing of decisions doesn’t mean that we don’t actually make the decisions themselves that are consequential.

Spontaneous activity

Aaron Schurger and colleagues have a nice paper in which they argue that Libet’s results can be explained by variations in spontaneous activity before actions are taken. They argue that the movement system is constantly experiencing sub-threshold variation in activity, so that at any particular point in time you are more or less close to performing any particular act. Participants in the Libet paradigm, asked to make a spontaneous act, take advantage of this variability – effectively lowering their threshold for action and waiting until the covert fluctuations are large enough to trigger a movement. Importantly, this reading weakens the link between the ‘onset’ of movements and the delayed subjective experience of making a movement. If the movement is triggered by random fluctuations (observable in the rise of the electrode signal) then there isn’t a distinct ‘decision to act’ in the motor system, so we can’t say that the subjective decision to act reliably comes afterwards.

The ‘only deterministic on average’ criticism

The specific electrode signal which is used to time the decision to move in the brain is called the readiness potential (RP). Electrode readings are highly variable, so the onset of the RP is a statistical artefact, produced by averaging over many trials (40 in Libet’s case). This means we lose the ability to detect, trial-by-trial, the relation between the brain activity related to movement and the subjective experience. Libet reports this in his original paper [1] (‘only the average RP for the whole series could be meaningfully recorded’, p634). On occasion the subjective decision time (which Libet calls W) comes before the time of even the average RP, not after (p635: “instances in which individual W time preceded onset time of averaged RP numbered zero in 26 series [out of 36] – which means that 28% of series saw at least one instance of W occurring before the RP).

The experiment showed strong reliability, but not complete reliability (the difference is described by Libet as ‘generally’ occurring and as being ‘fairly consistent’, p636). What happened next to Libet’s result is a common trick of psychologists. A statistical pattern is discovered and then reality is described as if the pattern is the complete description: “The brain change occurs before the choice”.

Although such generalities are very useful, they are misleading if we forget that they are only averagely true, not always true. I don’t think Libet’s experiment would have the imaginative hold if the result was summarised as “The brain change usually occurs before the choice”.

A consistent, but not universal, pattern in the brain before a choice has the flavour of a prediction, rather than a compulsion. Sure, before we make a choice there are antecedents in the brain – it would be weird if there weren’t – but since these don’t have any necessary consequence for what we choose, so what?

To my mind the demonstration that you can use fMRI to reproduce the Libet effect but with brain signals changing up to 10 seconds before the movement (and an above chance accuracy at predicting the movement made), only reinforces this point. We all believe that the mind has something to do with the brain, so finding patterns in the brain at one point which predict actions in the mind at a later point isn’t surprising. The fMRI result, and perhaps Libet’s experiment, rely as much on our false intuition about dualism as conclusively demonstrating anything new about freewill.

Link: my column Why do we intuitively believe we have free will?

Fifty psychological terms to just, well, be aware of

CC Licensed Photo by Flickr user greeblie. Click for source.Frontiers in Psychology has just published an article on ‘Fifty psychological and psychiatric terms to avoid’. These sorts of “here’s how to talk about” articles are popular but themselves can often be misleading, and the same applies to this one.

The article supposedly contains 50 “inaccurate, misleading, misused, ambiguous, and logically confused words and phrases”.

The first thing to say is that by recommending that people avoid certain words or phrases, the article is violating its own recommendations. That may seem like a trivial point but it isn’t when you’re giving advice about how to use language in scientific discussion.

It’s fine to use even plainly wrong terms to discuss how they’re used, the multiple meanings and misconceptions behind them. In fact, a lot of scientific writing does exactly this. When there are misconceptions that may cloud people’s understanding, it’s best to address them head on rather than avoid them.

Sometimes following the recommendations for ‘phrases to avoid’ would actually hinder this process.

For example, the piece recommends you avoid the term ‘autism epidemic’ as there is no good evidence that there is an actual epidemic. But this is not advice about language, it’s just an empirical point. According to this list, all the research that has used the term, to discuss the actual evidence in contrary to the popular idea, should have avoided the term and presumably referred to it as ‘the concept that shall not be named’.

The article also recommends against using ‘ambiguous’ words but this recommendation would basically kill the English language as many words have multiple meanings – like the word ‘meaning’ for example – but that doesn’t mean you should avoid them.

If you’re a fan of pedantry you may want to go through the article and highlight where the authors have used other ambiguous psychological phrases (starter for 10, “memory”) and post it to some obscure corner of the internet.

Many of the recommendations also rely on you agreeing with the narrow definition and limits of use that the authors premise their argument on. Do you agree that “antidepressant medication” means that the medication has a selective and specific effect on depression and no other conditions – as the authors suggest? Or do you think this just describes a property of the medication? This is exactly how medication description works throughout medicine. Aspirin is an analgesic medication and an anti-inflammatory medication, as well as having other properties. No banning needed here.

And in fact, this sort of naming is just a property of language. If you talk about an ‘off-road vehicle’, and someone pipes up to tell you “actually, off-road vehicles can also go on-road so I recommend you avoid that description” I recommend you ignore them.

The same applies to many of the definitions in this list. The ‘chemical imbalance’ theory of depression is not empirically supported, so don’t claim it is, but feel free to use the phrase if you want to discuss this misconception. Some conditions genuinely do involve a chemical imbalance though – like the accumulation of copper in Wilson’s disease, so you can use the phrase accurately in this case, being aware of how its misused in other contexts. Don’t avoid it, just use it clearly.

With ‘Lie detector test’ no accurate test has ever been devised to detect lies. But you may be writing about research which is trying to develop one or research that has tested the idea. ‘No difference between groups’ is fine if there is genuinely no difference in your measure between the groups (i.e. they both score exactly the same).

Some of the recommendations are essentially based on the premise that you ‘shouldn’t use the term except for how it was first defined or defined where we think is the authoritative source’. This is just daft advice. Terms evolve over time. Definitions shift and change. The article recommends against using ‘Fetish’ except for in its DSM-5 definition, despite the fact this is different to how it’s used commonly and how it’s widely used in other academic literature. ‘Splitting’ is widely used in a form to mean ‘team splitting’ which the article says is ‘wrong’. It isn’t wrong – the term has just evolved.

I think philosophers would be surprised to hear ‘reductionism’ is a term to be avoided – given the massive literature on reductionism. Similarly, sociologists might be a bit baffled by ‘medical model’ being a banned phrase, given the debates over it and, unsurprisingly, its meaning.

Some of the advice is just plain wrong. Don’t use “Prevalence of trait X” says the article because apparently prevalence only applies to things that are either present or absent and “not dimensionally distributed in the population, such as personality traits and intelligence”. Many traits are defined by cut-off scores along dimensionally defined constructs, making them categorical. If you couldn’t talk about the prevalence in this way, we’d be unable to talk about prevalence of intellectual disability (widely defined as involving an IQ of less than 70) or dementia – which is diagnosed by a cut-off score on dimensionally varying neuropsychological test performance.

Some of the recommended terms to avoid are probably best avoided in most contexts (“hard-wired”, “love molecule”) and some are inherently self-contradictory (“Observable symptom”, “Hierarchical stepwise regression”) but again, use them if you want to discuss how they’re used.

I have to say, the piece reminds me of Stephen Pinker’s criticism of ‘language mavens’ who have come up with rules for their particular version of English which they decide others must follow.

To be honest, I think the Frontiers in Psychology article is well-worth reading. It’s a great guide to how some concepts are used in different ways, but it’s not good advice for things to avoid.

The best advice is probably: communicate clearly, bearing in mind that terms and concepts can have multiple meanings and your audience may not be aware of which you want to communicate, so make an effort to clarify where needed.

Link to Frontiers in Psychology article.