Posts archived in Psychology A2


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Risky behaviour

June 12, 2011 by .

One of the explanations for addiction is that some individuals have a biological predisposition because they inherit a particular form of dopamine receptor gene (if you want an explanation of dopamine receptor genes see second paragraph). An interesting link has been made between these genes and evolution. The argument goes that the dispersal of our distant ancestors from Africa was related to riskiness. Individuals with a predisposition to be impulsive and risky rather than careful and reflective would be more likely to explore and find new, desirable environments and would also cope better with new, challenging situations. Recent research has indeed found a link between specific dopamine genes and migration patterns i.e. migrants were more likely to have the version of the dopamine receptor gene that codes for risky behaviour. This shows that the gene has had an adaptive function, and may continue to do so.

Understanding dopamine receptor genes: There are different types of dopamine receptor such as D1R, D2R etc. (D for dopamine, R for receptor and the number denotes the type). The receptor is called D1R and the gene for that receptor is called DRD1, or D2R and DRD2 (which seems confusing to me, but there it is). For any gene there are different forms or allelles. So, for example, we all have a gene for D2R but the form of that gene differs. One person may have the G allele (which is associated with aggression) or the 1A allele (associated with addiction). In the study cited above (Matthews and Butler, 2011) the DRD4 gene was studied and the 7R and 2R versions were associated with risky behaviour whereas the 4R version was linked to being even tempered.

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Blue light bad

May 27, 2011 by .

Early temporal isolation studies overlooked the fact that artificial light has an effect on circadian rhythms but more recent research showed that even fairly dim lighting may reset the SCN (suprachiasmatic nucleus). Even more recently research has found that blue light is particularly effective – for good and bad.

The story starts with blind people – some blind have considerable difficulties with their circadian rhythms because their insensitivity to light means that their body rhythms are constantly fluctuating. However, this is not true of all blind people. It seems that the eye has special light receptors related to the circadian rhythm and these feed directly into the SCN (Czeisler et al., 1995). Other research has found that these special cells are particularly sensitive to blue light. For example Kayumov et al. (2005) found that volunteers doing simulated shift work had reduced melatonin production if they were exposed to bright light but not if they wore goggles that filtered out blue light. Dim lighting also did not result in reduced levels of melatonin.

You may ask ‘Where did the melatonin come in’? Light resets the SCN and also suppresses the production of melatonin (when it gets dark, melatonin levels rise making us sleepy). Suppression of melatonin has been linked to cancer, obesity, diabetes and cardiovascular disease. So shiftworkers doing night work with bright lighting are exposed to risks that could be prevented if the lighting was dim or blue light was filtered out. In fact the same is true for all of us, at night it is better to sit in dimly lit rooms and use lighting with less blue in it.

 

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Mind changers

April 1, 2011 by .

Over the last few years the BBC has broadcast an excellent series on research studies that have changed our understanding of the human mind, presented by Claudia Hammond (some of you may have heard her speak at a recent student conference in London). The BBC has now decided to make them all available for download here. Topics covered include Bandura’s Bobo doll study, Rosenhan’s Pseudo-patient study, Kohlberg’s Heinz dilemma, The Hawthorne effect, Mary Ainsworth’s research. In total there are 15 programmes each 28 minutes in length. On Sunday 17 April there is a new series starting with a programme on Elizabeth Loftus and Eyewitness Testimony.

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ECT – good or bad?

March 4, 2011 by .

The American Psychiatric Association (APA) has been arguing in favour of ECT as a safe treatment for severe mental illness, according to a short piece in the current issue of the BPS magazine The Psychologist. The APA claims that ECT is effective 80% of the time and there is no evidence for any associated brain damage.

On the other hand a recent review by Bentall and Read (2010, see here) concluded that any benefits of ECT, when they arise, are minimal, short-lived and come with a significant risk of memory impairment and a slight risk of death. This conclusion was based on a review of studies over the last 60 years where the use of ECT for depression or schizophrenia was compared to a placebo control procedure. Bentall and Read’s final word is that the evidence is so poor that it’s use cannot be scientifically-justified.

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It seems that dolphins don’t dream

January 25, 2011 by .

In Chapter 1 (Biological rhythms and sleep) of our A2 Complete Companion there is a contradiction (kindly pointed out by Ruth Bailey of Akeley Wood School). On page 13  the text says that dolphins don’t have REM sleep whereas on page 14 the graph indicates a significant amount of REM sleep in dolphin. So which is correct?

The data for the graph was taken from a study Lyamin et al. (2004) of one dolphin, reported by the Phylogeny of Sleep Project (you can see the dolphin data here). As pointed out in our textbook much of the data about sleep is actually derived from very small samples and research conducted under poorly controlled conditions.

All of the other dolphin studies given by the Phylogeny of Sleep Project did not record the amount of REM sleep which is why we used the data from Lyamin et al. However this data is misleading as the general view appears to be that (REM) sleep is either absent in cetaceans (e.g. dolphins) or occupies an extremely small proportion of the day – an absolute maximum of 15 min each day (Manger et al., 2003). In fact a recent paper published by Lyamin et al. (2008) states that ‘We find that for cetaceans sleep is characterized by USWS [unihemispheric slow wave sleep] [and] a negligible amount or complete absence of rapid eye movement (REM) sleep’.

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Getting Type 1 and 2 errors confused

January 4, 2011 by .

Type 1 and 2 errors are not easy to understand and recently one student (thank you Laura Hastings) wrote in to ask if we were also confused (!) and had made a mistake with Type 1 and 2 errors in our AQA A A2 book. Fortunately we hadn’t but the explanation was a bit unclear. On page 266 (Chapter on Anomalistic Psychology) it says:

Causal thinking evolved because it allows people to understand and control their environment, i.e. to be able to predict that, for example, if you eat a red mushroom you will die. This causal thinking is adaptive but may sometimes lead to Type 1 errors – where you believe something is true when it isn’t, for example you believe that tying your shoes laces twice causes luck.

The problematic phrase is ‘where you believe something is true when it isn’t’. Laura was confused because a Type 1 error is defined on page 300 as ‘when a null hypothesis is rejected when it is true’. So it sounds like we got it wrong – but in fact both Type 1 and Type 2 errors are ‘where you believe something that isn’t true’:

  • Type 1 error (false positive) – you believe the null hypothesis isn’t true (and reject it) but in reality the null hypothesis is true. So, in the case of shoe laces you believe shoe laces and luck are linked but, in reality, there is no link. Or you avoid mushrooms for ever after because you think they will make you die but this link is mistaken.
  • Type 2 error (false negative) – you believe the null hypothesis is true (and accept it) when in reality the null hypothesis is not true. In the case of shoe laces and luck, you believe tying your shoe laces twice has no effect on luck but in fact it has. Or you believe that red mushrooms don’t cause death but they do.

The point is that we err on the side of making Type 1 errors (and believing erroneous causal relationships) because we might otherwise make Type 2 errors.

As for the text book, it would be better if it said ‘Type 1 errors – where you believe the null hypothesis is wrong when it isn’t’.

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Can you tell if someone throws like a girl?

December 26, 2010 by .

Interesting range of online experiments involving bio-motion here

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Is it when you sleep, not how much, that counts?

December 14, 2010 by .

A small study of Canadian infants and toddlers found that those who slept most at night were making significantly more progress in executive functions than those who slept less at night, even if the latter group also had daytime sleep. These functions include impulse control, memory and mental flexibility. The researchers controlled for parents’ education and income and children’s general cognition, but the link between night-time sleep and development of cognitive skills remained. These finding support similar research findings on schoolchildren.

Might this also apply to older childern and adults? That would be interesting to know!
Annie Bernier, Stephanie M. Carlson, Stéphanie Bordeleau, Julie Carrier. Relations Between Physiological and Cognitive Regulatory Systems: Infant Sleep Regulation and Subsequent Executive Functioning. Child Development, 2010; 81 (6)

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How the SCN sees light

December 8, 2010 by .

It’s been known for ages that information on light levels is passed from the two retinas via a special small nerve from each eye to the SCN, but the mechanism of this is now more clear. As well as rods and cones, cells which are sensitive to light and give us black-and-white and colour vision there is a third type of light-sensitive retinal cell. These are far less in number than rods and cones, and react to light by expressing the pigment melanopsin, so they are known as mRGCs (melanopsin-expressing retinal ganglion cells). Not only do these cells send information to the SCN but they also control pupil size. And now it seems they also contribute to our visual image formation as axons from the mRGCs have been traced onwards from the SCN to visual processing centres. What does this imply? It gives some idea of how seriously sight impaired people can still detect levels of brightness, plus the possibility in the future of engineering melanopsin-expressing cells to improve or restore sight.

Fred Rieke, Timothy M. Brown, Carlos Gias, Megumi Hatori, Sheena R. Keding, Ma’ayan Semo, Peter J. Coffey, John Gigg, Hugh D. Piggins, Satchidananda Panda, Robert J. Lucas. Melanopsin Contributions to Irradiance Coding in the Thalamo-Cortical Visual System. PLoS Biology, 2010; 8 (12)

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A proposal to classify happiness as a psychiatric disorder

December 6, 2010 by .

It is proposed that happiness be classified as a psychiatric disorder and be included in future editions of the major diagnostic manuals under the new name: major affective disorder, pleasant type. In a review of the relevant literature it is shown that happiness is statistically abnormal, consists of a discrete cluster of symptoms, is associated with a range of cognitive abnormalities, and probably reflects the abnormal functioning of the central nervous system. One possible objection to this proposal remains–that happiness is not negatively valued. However, this objection is dismissed as scientifically irrelevant.

link

via null device

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