Thoughts on Psychology

Just another site

Archive for January 2012

Learning about the paranormal from a carton of eggs

with 5 comments


I’m sometimes asked how psychology might explain events that seem so strange that they suggest the existence of paranormal activity, for example when you’re thinking about a friend and how you haven’t talked to them for a while, and then the phone rings and it’s them. These events seem so very unlikely, it seems impossible that they could happen by chance. The explanation that it’s just a coincidence doesn’t seem very persuasive. However, sometimes an unpersuasive reason is the right one, and the reason why unusual events sometimes occur comes down to the law of large numbers.
Any event that can be possible, including bizarre coincidences, has some chance of it happening, even if that chance is very small. However, there are so many events, and so many people to potentially experience them, that even the most unlikely of coincidences is likely to happen now and again. Hence the picture above. I was making an omelet last night, and was surprised to find when I cracked the first egg that it had a double yolk: I haven’t had that happen to me for a long time, probably because the chances of an egg having a double yolk are about one in a thousand. I was considerably more surprised when I cracked a second egg, and found that it too had a double yolk. If the events (each egg crack) are independent (though they probably aren’t), then the chances of that happening are one in a million. When I cracked the third egg and found another double yolk I must confess to feeling a bit spooked. When the fourth egg was a single yolk I was a little disappointed, but also a little relieved: it meant I could stop looking for pixies at the bottom of the garden! Then the fifth and sixth eggs were also double yolks, and I started feeling spooked again. Six eggs produced 11 yolks, pictured above. The chances of that, if the events are independent, are infinitesimal: let’s say one in a billion for a nice round number. And yet, it happened. Even if the chances are one in a billion, given the number of people buying eggs on a regular basis then there will be times that people find multiple instances of double yolks.
I thought five out of six was pretty spooky, but then I found this: six out of six
The Mail quote odds of a trillion to one for that, again based on the events being independent. As some of the comments point out though, it’s unlikely that the events are independent, and the odds of a double yolk are probably greater than one in a thousand for large eggs (eggs with a double yolk are more likely to be large), and perhaps for free range eggs. Still, I buy these eggs regularly, and have never had a double yolk before, so it’s still a pretty unlikely event.
I refuse to believe the commenter in the mail post who claims 11 out of 12: that’s too far fetched even for me!


Written by daijones

January 29, 2012 at 9:58 pm

Posted in Uncategorized

It’s not just me

leave a comment »

Good post here on problems with the BBC’s science reporting:
The BBC’s problem with science

Written by daijones

January 27, 2012 at 1:16 am

Posted in Uncategorized

Keeping an eye on the diagnostic manual

with 2 comments

A useful website here keeping an eye on the controversial development of version 5 of the American Psychiatric Association’s diagnostic manual. The development raises a whole range of issues around the definition of abnormality, the medicalisation of psychological conditions, and the role of drug companies in pushing particular kinds of syndromes, diagnoses, and treatments. A case in point of the latter is female hypoactive sexual desire disorder, being pushed as a neurologically founded disorder in individual women best treated through drug therapy, with no reference to the conditions of “sufferer’s” lives, or the quality of relationships, or the performances of their partners; and limited attention to psychological rather than chemical intervention. Good news for the drug companies, bad news for women. There’s a great post on this here.

Written by daijones

January 7, 2012 at 6:09 pm

Posted in Uncategorized

Gendered therapy

leave a comment »

Nice example of how psychological diagnosis and treatment has been used to reinforce and impose stereotypical behaviour:

Advances in the History of Psychology

Written by daijones

January 2, 2012 at 10:47 pm

More shoddy science reporting from the BBC

leave a comment »

An exciting headline on the BBC News website recently:

Alzheimer’s: Diet ‘can stop brain shrinking’

Alzheimer’s is a devastating illness and anything that can help prevent or delay its onset, or lessen it’s severity, is to be welcomed. The headline, and in part the article that follows, suggest that diet can reduce brain shrinkage in later life and so act protectively against Alzheimer’s.┬áThere are a couple of problems here though, that should be quickly apparent if you read the article with a sceptical eye. The first is in the suggestion that the article has anything to do with Alzheimer’s: the research wasn’t conducted on Alzheimer’s sufferers, and participants weren’t followed longitudinally to see if there was a differential incidence of Alzheimer’s developing. So, the research can’t actually tell us anything about Alzheimer’s. To be fair to the article, this is mentioned. In the penultimate paragraph.

A bigger problem, potentially, is with the interpretation of the research itself. The article takes an unambiguous position that a diet high in vitamins and omega 3 fatty acids caused a reduction in brain shrinkage with age. However, the research didn’t find this. Rather, it found a correlation between blood nutrients and brain volume: as a quasi-experiment, even if the test used a difference statistic then the result is essentially correlational. And correlation doesn’t prove causation. There are a number of possible reasons for the results found, given the pre-existing evidence that education and intellectual effort increases brain complexity and volume. Off the top of my head, it may be that people who are well educated tend to have higher brain volumes, and also tend to eat healthier diets. Or people from higher socio-economic groups tend to be both more highly educated, and are more likely to follow (and be able to afford) a healthy diet.

To eliminate these possibilities, you’d hope that the original research controlled for factors including education and socio-economic status. It’s behind a paywall so I can’t check, but if they did then the BBC didn’t think to mention it. The other result reported, that there was a difference in performance on cognitive tasks in a sample of people without clinical deficits, suggests that there’s some relationship between diet and cognitive performance, but without knowing the educational history of the participants it’s impossible to decide whether diet causes differences in performance, as the article suggests; or whether it’s again a matter of better educated people tending to have better diets. The latter is certainly a strong possibility, and you’d hope that the health editor who wrote the article would discuss this.

Written by daijones

January 1, 2012 at 10:25 pm