What triggers that feeling of being watched?

You feel somebody is looking at you, but you don’t know why. The explanation lies in some intriguing neuroscience and the study of a strange form of brain injury.

Something makes you turn and see someone watching you. Perhaps on a busy train, or at night, or when you’re strolling through the park. How did you know you were being watched? It can feel like an intuition which is separate from your senses, but really it demonstrates that your senses – particularly vision – can work in mysterious ways.

Intuitively, many of us might imagine that when you look at something with your eyes, signals travel to your visual cortex and then you have the conscious experience of seeing it, but the reality is far weirder.

Once information leaves our eyes it travels to at least 10 distinct brain areas, each with their own specialised functions. Many of us have heard of the visual cortex, a large region at the back of the brain which gets most attention from neuroscientists. The visual cortex supports our conscious vision, processing colour and fine detail to help produce the rich impression of the world we enjoy. But other parts of our brain are also processing different pieces of information, and these can be working away even when we don’t – or can’t – consciously perceive something.

The survivors of neural injury can cast some light on these mechanisms. When an accident damages the visual cortex, your vision is affected. If you lose all of your visual cortex you will lose all conscious vision, becoming what neurologists call ‘cortically blind’. But, unlike if you lose your eyes, cortically blind is only mostly blind – the non-cortical visual areas can still operate. Although you can’t have the subjective impression of seeing anything without a visual cortex, you can respond to things captured by your eyes that are processed by these other brain areas.

In 1974 a researcher called Larry Weiskrantz coined the term ‘blindsight’ for the phenomenon of patients who were still able to respond to visual stimuli despite losing all conscious vision due to destruction of the visual cortex. Patients like this can’t read or watch films or anything requiring processing of detail, but they are – if asked to guess – able to locate bright lights in front of them better than mere chance. Although they don’t feel like they can see anything, their ‘guesses’ have a surprising accuracy. Other visual brain areas are able to detect the light and provide information on the location, despite the lack of a visual cortex. Other studies show that people with this condition can detect emotions on faces and looming movements.

More recently, a dramatic study with a blindsight patient has shown how we might be able feel that we are being looked at, without even consciously seeing the watchers’ face. Alan J Pegna at Geneva University Hospital, Switzerland, and team worked with a man called TD (patients are always referred to by initials only in scientific studies, to preserve anonymity). TD is a doctor who suffered a stroke which destroyed his visual cortex, leaving him cortically blind.

People with this condition are rare, so TD has taken part in a string of studies to investigate exactly what someone can and can’t do without a visual cortex. The study involved looking at pictures of faces which had their eyes directed forward, looking directly at the viewer, or which had their eyes averted to the side, looking away from the viewer. TD did this task in an fMRI scanner which measured brain activity during the task, and also tried to guess which kind of face he was seeing. Obviously for anyone with normal vision, this task would be trivial – you would have a clear conscious visual impression of the face you were looking at at any one time, but recall that TD has no conscious visual impression. He feels blind.

The scanning results showed that our brains can be sensitive to what our conscious awareness isn’t. An area called the amygdala, thought to be responsible for processing emotions and information about faces, was more active when TD was looking at the faces with direct, rather than averted, gaze. When TD was being watched, his amygdala responded, even though he didn’t know it. (Interestingly, TD’s guesses as to where he was being watched weren’t above chance, and the researchers put this down to his reluctance to guess.)

Cortical, conscious vision, is still king. If you want to recognise individuals, watch films or read articles like this you are relying on your visual cortex. But research like this shows that certain functions are simpler and maybe more fundamental to survival, and exist separately from our conscious visual awareness.

Specifically, this study showed that we can detect that people are looking at us within our field of view – perhaps in the corner of our eye – even if we haven’t consciously noticed. It shows the brain basis for that subtle feeling that tells us we are being watched.

So when you’re walking that dark road and turn and notice someone standing there, or look up on the train to see someone staring at you, it may be your nonconscious visual system monitoring your environment while you’re conscious attention was on something else. It may not be supernatural, but it certainly shows the brain works in mysterious ways.

This is my BBC Future column from last week. The original is here.

This map shows what white Europeans associate with race – and it makes for uncomfortable reading

File 20170425 12650 16jxfww
The ConversationThis new map shows how easily white Europeans associate black faces with negative ideas. The ConversationSince 2002, hundreds of thousands of people around the world have logged onto a website run by Harvard University called Project Implicit and taken an “implicit association test” (IAT), a rapid-response task which measures how easily you can pair items from different categories.To create this new map, we used data from a version of the test which presents white or black faces and positive or negative words. The result shows how easily our minds automatically make the link between the categories – what psychologists call an “implicit racial attitude”.Each country on the map is coloured according to the average score of test takers from that country. Redder countries show higher average bias, bluer countries show lower average bias, as the scale on the top of the map shows.Like a similar map which had been made for US states, our map shows variation in the extent of racial bias – but all European countries are racially biased when comparing blacks versus whites.

In every country in Europe, people are slower to associate blackness with positive words such as “good” or “nice” and faster to associate blackness with negative concepts such as “bad” or “evil”. But they are quicker to make the link between blackness and negative concepts in the Czech Republic or Lithuania than they are in Slovenia, the UK or Ireland.

No country had an average score below zero, which would reflect positive associations with blackness. In fact, none had an average score that was even close to zero, which would reflect neither positive nor negative racial associations.

A screeshot from the online IAT test.
IAT, Project Implict

Implicit bias

Overall, we have scores for 288,076 white Europeans, collected between 2002 and 2015, with sample sizes for each country shown on the left-hand side.

Because of the design of the test it is very difficult to deliberately control your score. Many people, including those who sincerely hold non-racist or even anti-racist beliefs, demonstrate positive implicit bias on the test. The exact meaning of implicit attitudes, and the IAT, are controversial, but we believe they reflect the automatic associations we hold in our minds, associations that develop over years of immersion in the social world.

Although we, as individuals, may not hold racist beliefs, the ideas we associate with race may be constructed by a culture which describes people of different ethnicities in consistent ways, and ways which are consistently more or less positive. Looked at like this, the IAT – which at best is a weak measure of individual psychology – may be most useful if individuals’ scores are aggregated to provide a reflection on the collective social world we inhabit.

The results shown in this map give detail to what we already expected – that across Europe racial attitudes are not neutral. Blackness has negative associations for white Europeans, and there are some interesting patterns in how the strength of these negative associations varies across the continent.

North and west Europe, on average, have less strong anti-black associations, although they still have anti-black associations on average. As you move south and east the strength of negative associations tends to increase – but not everywhere. The Balkans look like an exception, compared to surrounding countries. Is this because of some quirk about how people in the Balkans heard about Project Implicit, or because their prejudices aren’t orientated around a white-black axis? For now, we can only speculate.

Open questions

When interpreting the map there are at least two important qualifications to bear in mind.

The first is that the scores only reflect racial attitudes in one dimension: pairing white/black with goodness/badness. Our feelings about ethnicity have many more dimensions which aren’t captured by this measure.

The second is that the data comes from Europeans who visit the the US Project Implicit website, which is in English. We can be certain that the sample reflects a subset of the European population which are more internet-savvy than is typical. They are probably also younger, and more cosmopolitan. These factors are likely to underweight the extent of implicit racism in each country, so that the true levels of implicit racism are probably higher than shown on this map.

This new map is possible because Project Implicit release their data via the Open Science Framework. This site allows scientists to share the raw materials and data from their experiments, allowing anyone to check their working, or re-analyse the data, as we have done here. I believe that open tools and publishing methods like these are necessary to make science better and more reliable.

This article was originally published on The Conversation. Read the original article.

Edit 4/5/17. The colour scale chosen for this map emphasises the differences between countries. While that’s most important for working out what drives IAT scores, the main take-away from the map is that all of Europe is considerably not neutral. That conclusion is supported by a continuous colour scale, as used in this version of the map here

neurotransmitter fashion

A graph of scientific articles published per year which mention four major neurotransmitters in their title:

What I take from this is

  • Dopamine is king! And with great popularity, comes great misrepresentation.
  • What happened to glutamate research in the mid 1990s?
  • The recent hype about oxytocin doesn’t seem to be driven by a spike in the primary literature.
  • Nor does the hype about serotonin. Yes, publications increase on this neurotransmitter, but not compared to glutamate. And most people haven’t heard about glutamate, despite it being more abundant.

Technical note: I scraped the data from google scholar using scholar.py by Christian Kriebich

Update: here’s the raw data, should you want it

hormones, brain and behaviour, a not-so-simple story

There’s a simple story about sex differences in cognition, which traces these back to sex differences in early brain development, which are in turn due to hormone differences. Diagrammatically, it looks something like this:

simpleCordelia Fine’s “Delusions of Gender” (2010) accuses both scientists and popularisers of science with being too ready to believe overly simple, and biologically fixed, accounts of sex differences in cognition.

There is an undeniable sex difference in foetal testosterone in humans at around 6-8 weeks after conception. In Chapter 9 of her book, Fine introduces Simon Baron-Cohen, who seems to claim that this surge in male hormones is the reason why men are more likely to be Autistic, and why no woman had ever won the Fields Medal. So, diagrammatically:

simple_mathsThis account may appear, at first, compelling, perhaps because of its simplicity. But Fine presents us with an antidote for this initial intuition, in the form of the neurodevelopmental story of a the spinal nucleus of the bulbocavernosus (SNB), a subcortical brain area which controls muscles at the base of the penis.

Even here, the route between hormone, brain difference and behaviour is not so simple, as shown by neat experiments with rats by Celia Moore, described by Fine (p.105 in my edition). Moore showed that male rat pups are licked more by their mothers, and that this licking is due to excess testosterone in their urine. Mothers which couldn’t smell, licked male and female pups equally, and female pups injected with testosterone were licked as much as male pups. This licking had an extra developmental effect on the SNB, which could be mimicked by manual brushing of a pup’s perineum. Separate work showed that testosterone doesn’t act directly on the neurons of the SNB, but instead prevents cell death in the SNB by preserving the muscles which it connects to (in males). So, diagrammatically:

snbOne review, summarising what is known about the development of the SNB, writes ‘[There is] a life-long plasticity in even this simple system [and] evidence that adult androgens interact with social experience in order to affect the SNB system’. Not so simple!

What I love about this story is the complexity of developmental causes. Even in the rat, not the human! Even in the subcortex, not the cortex! Even in a brain area which direct controls a penis reflex. Fine’s implicit question for Baron-Cohen seems to be: If evolution creates this level of complexity for something as important for reproductive function, what is likely for the brain areas responsible for something as selectively-irrelevant as winning prizes at Mathematics?

Notice also the variety of interactions, not just the number : hormones -> body, body -> sensation in mother’s brain, brain -> behaviour, mother’s behaviour -> pup’s sensation, sensation -> cell growth. This is a developmental story which happens across hormones, brain, body, behaviour and individuals.

Against this example, sex differences in cognition due to early hormone differences look far from inevitable, and the simple hormone-brain-behaviour looks like a crude summary at best. Whether you take it to mean that sex differences in hormones have multiple routes to generate sex differences in cognition (a ‘small differences add up’ model) or that sex differences in hormones will cancel each other out, may depend on your other assumptions about development. At a minimum, the story of the SNB shows that those assumptions are worth checking.

Previously: gender brain blogging

Paper: Moore, C. L., Dou, H., & Juraska, J. M. (1992). Maternal stimulation affects the number of motor neurons in a sexually dimorphic nucleus of the lumbar spinal cord. Brain research, 572(1), 52-56.

Source for the 2009 claim by Baron-Cohen claim that foetal hormones explain why no woman has won the Fields medal: Autism test ‘could hit maths skills’.

In 2014 Maryam Mirzakhabi won the Fields medal.

Diagrams made with draw.io

Why women don’t report sexual harassment

189px-milgram_experimentJulie A. Woodzicka (Washington and Lee University) and Marianne LaFrance (Yale) report an experiment reminiscent of Milgram’s famous studies of obedience to authority. Reminiscent both because it highlights the gap between how we imagine we’ll respond under pressure and how we actually do respond, and because it’s hard to imagine an ethics review board allowing it.

The study, reported in the Journal of Social Issues in 2001, involved the following (in their own words):

we devised a job interview in which a male interviewer asked female job applicants sexually harassing questions interspersed with more typical questions asked in such contexts.

The three sexually harassing questions were (1) Do you have a boyfriend? (2) Do people find you desirable? and (3) Do you think it is important for women to wear bras to work?

Participants, all women, average age 22, did not know they were in an experiment and were recruited through posters and newspaper adverts for a research assistant position.

The results illuminated what targets of harassment do not do. First, no one refused to answer: Interviewees answered every question irrespective of whether it was harassing or nonharassing. Second, among those asked the harassing questions, few responded with any form of confrontation or repudiation. Nonetheless, the responses revealed a variety of ways that respondents attempted to circumvent the situation posed by harassing questions.

Just as with the Milgram experiment, these results contrast with how participants from a companion study imagined they would respond when the scenario was described to them:

The majority (62%) anticipated that they would either ask the interviewer why he had asked the question or tell him that it was inappropriate. Further, over one quarter of the participants (28%) indicated that they would take more drastic measures by either leaving the interview or rudely confronting the interviewer. Notably, a large number of respondents (68%) indicated that they would refuse to answer at least one of the three harassing questions.

Part of the difference, the researchers argue, is that women imagining the harassing situation over-estimate the anger they will feel. When confronted with actual harassment, fear replaces anger, they claim. Women asked the harassing questions reported significantly higher rates of fear than women asked the merely surprising questions. Coding of facial expressions during the (secretly videoed) interviews revealed that the harassed women also smiled more – fake (non-Duchenne) smiles, presumably aimed at appeasing a harasser that they felt afraid of.

The research report doesn’t indicate what, if any, ethical review process the experiment was subject to.

Obviously it is an important topic, with disturbing and plausible findings. The researchers note that courts have previously interpreted inaction following harassment as indicative of some level of consent. But, despite the real-world relevance, is it a topic that is it important enough to justify employing a man to sexually harass unsuspecting women?

Reference: Woodzicka, J. A., & LaFrance, M. (2001). Real versus imagined gender harassment. Journal of Social Issues, 57(1), 15-30.

Previously: a series of Gender Brain Blogging

Much more previously: an essay I wrote arguing that moral failures are often defined by failures of imagination, not of reason: The Narrative Escape

The Social Priming Studies in “Thinking Fast and Slow” are not very replicable

train_wreck_at_montparnasse_1895In Daniel Kahneman’s “Thinking Fast and Slow” he introduces research on social priming – the idea that subtle cues in the environment may have significant, reliable effects on behaviour. In that book, published in 2011, Kahneman writes “disbelief is not an option” about these results. Since then, the evidence against the reliability of social priming research has been mounting.

In a new analysis, ‘Reconstruction of a Train Wreck: How Priming Research Went off the Rails‘, Ulrich Schimmack, Moritz Heene, and Kamini Kesavan review chapter 4 of Thinking Fast and Slow, picking out the references which provide evidence for social priming and calculating how statistically reliable they:

Their conclusion:

The results are eye-opening and jaw-dropping.  The chapter cites 12 articles and 11 of the 12 articles have an R-Index below 50.  The combined analysis of 31 studies reported in the 12 articles shows 100% significant results with average (median) observed power of 57% and an inflation rate of 43%.  …readers of… “Thinking Fast and Slow” should not consider the presented studies as scientific evidence that subtle cues in their environment can have strong effects on their behavior outside their awareness.

The argument is that the pattern of 100% significant results is near to impossible, even if the effects known were true, given the weak statistical power of the studies to detect true effects.

Remarkably, Kahneman responds in the comments:

What the blog gets absolutely right is that I placed too much faith in underpowered studies. …I have changed my views about the size of behavioral priming effects – they cannot be as large and as robust as my chapter suggested.

The original analysis, and Kahneman’s response are worth reading in full. Together they give a potted history of the replication crisis, and a summary of some of the prime causes (e.g. file draw effects), as well as showing off how mature psychological scientists can make, and respond to critique.

Original analysis: ‘Reconstruction of a Train Wreck: How Priming Research Went off the Rails‘, Ulrich Schimmack, Moritz Heene, and Kamini Kesavan. (Is it a paper? Is it a blogpost? Who knows?!)

Kahneman’s response

Sex differences in cognition are small

Lately I’ve been thinking about sex differences in brain and cognition. There are undeniable differences in the physical size of the brain, and different brain areas, even if there are no ‘female’ and ‘male’ brains categorically. These physical differences do not translate directly into commensurate differences in cognition. Indeed, there is support for a ‘gender similarities hypothesis’ which asserts that on most measures there is no difference between men and women.

Most, but maybe not all. There are a few areas of fundamental cognitive ability where gender differences seem to persist – mental rotation, vocabulary and maybe maths. But these differences are small. To see how small, I put them on the same chart with the physical differences and a few other behavioural differences for perspective.

Standardised mean differences (Cohen’s d effect size) for various gender differences in brain, behaviour and cognition:

gender_effectsReferences and calculations at the end of this post, below the fold. And if you need a primer on what is meant by standardised difference then go here.

Even with these, small, observed differences in cognition, we don’t know what proportion is due to contingent facts, such as the different experience and expectations men and women encounter in their lifetimes, and what proportion is immutable consequence of genetic difference in sex.

One possibility for why there is a mismatch between physical differences in the brain and cognitive differences is the possibility that structural differences between male and female brains may actually serve to support functional similarity, not difference.

For more, so much more, on this, see the special issue of Journal of Neuroscience Research (January/February 2017) on An Issue Whose Time Has Come: Sex/Gender Influences on Nervous System Function.

Includes: Grabowska, A. (2017). Sex on the brain: Are gender‐dependent structural and functional differences associated with behavior?. Journal of Neuroscience Research, 95(1-2), 200-212.

Previously: Gender brain blogging

Continue reading “Sex differences in cognition are small”