Are we fooled by prices ending in 99?

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There is an Ikea advert on TV at the moment for a dishwasher. It starts off with a question: “How much is a dishwasher?”, and proceeds to suggest some answers: £500? £400? £300? Soon the punchline is delivered – that Ikea sell a dishwasher for under £200. My advertising savvy eight-year old and I look up from our lego to see that the Ikea dishwasher is indeed under £200. But only just. The ad proudly proclaims that an Ikea dishwasher will set you back by just £199. Daughter and I debate whether this is honest of Ikea or whether it is more like a trick. Ok, the dishwasher is technically under £200. But you wouldn’t be able to do much with the change. Around the same time a student knocks on my door looking for a psychology dissertation supervisor in behavioural economics. It’s not one of my research areas but I’ve read Freakonomics and The Undercover Economist and I’m interested. She mentions price anchoring and I remember the Ikea dishwasher ad. “Like prices ending in 99?”, I ask. “Maybe”, she says.

The idea of prices ending in 99 resurfaces that evening, and from the sofa I use my smart phone to search the psychology research database “PsycInfo”. I find two fascinating and cool psychology experiments that address the very question of whether people are fooled by prices ending in 99. They are both written by Robert M. Schindler of Rutgers University, New Jersey. In fact it seems that he is THE guy for scientific investigations of prices ending in 99.

In the first paper, published in 1996, the researchers persuaded a real company, a mail order company specialising in women’s clothing, to make some subtle changes to their catalogue. Three versions were produced all of which were identical apart from the prices of the items on sale. In one version of the catalogue all item prices ended in 88, in a second version all item prices ended in 99, while in a third all item prices ended in 00. So, to provide an example, a scarf was advertised at $17.88 in the first catalogue, at $17.99 in the second catalogue and at $18.00 in the third catalogue. It was arranged for each catalogue to be mailed out to a large number of customers from the company’s database. Then all the researchers had to do was wait and see how buying patterns varied according to the different catalogues that had been circulated.

Over the next 6-months nearly 3,000 customers bought from the catalogues. Intriguingly, customers who bought from the 99-ending catalogue spent more money on average than those who bought from the other two catalogues. The average spend for the 99-ending catalogue was $59.99, compared with $50.00 for the 00-ending catalogue and $57.51 for the 88-ending catalogue. A statistical analysis indicated that these different spending levels were not merely chance fluctuations. In addition, more customers bought from the 99-ending catalogue than the other two versions, although the difference in customer numbers was not that large, and could have been a chance fluctuation.

Finding that people spent more money when buying items priced with 99 endings compared with 00 endings indicates that the pricing strategy influenced purchasing behaviour. Advertising items at one cent below the round dollar price lead to a greater average spend per consumer. It’s not clear from this how the 99-ending price effect works. Presumably the consumers somehow came to believe that the 99-ending priced items were better bargains, possibly because they seemed cheaper. I’ll return to how the 99-ending price effect works later.

You might be thinking that, although the study shows a 99-ending price effect, it only applies to a certain kind of person. Perhaps only less well-off or less well-educated people tended to shop from mail order catalogues in the pre-internet era. I should also point out that as these were women’s clothing catalogues it is likely that the majority of the purchasers were women. In other words, perhaps only some people are fooled by prices ending in 99 – perhaps less-well educated people, and perhaps women. Well, you could think that. But a second more recent study carried out with male and female university students as participants will most likely alter this opinion.

The second study was carried out with 122 students of Eastern Illinois University and was published in 2005. This time participants sat at a computer and were presented with on-screen instructions asking them to consider how many of a selection of items they thought they could buy with $73.00. They considered items one by one, and item prices ended either in 99 or 00. The items cost $3, $4, $5 or $6 in the 00-ending category, or $2.99, $3.99, $4.99 or $5.99 in the 99-ending category. Half of the participants were asked to think quickly and guess if necessary, while the other half were asked to think carefully before responding.

Now - if people are fooled into thinking items priced with 99-endings are significantly cheaper (more than one cent cheaper) than items priced with 00-endings, then they should overestimate the number of items priced with 99-endings that can be bought (and overestimate by more than the one-cent difference). And they did.

The participants estimated that, on average, 5% more items could be purchased when the price ended in 99 than when the price was one cent more. Again, a statistical analysis indicated that this difference was not a chance fluctuation. This 5% margin was much larger than the actual margin of price difference, which was never larger than 0.3% (in the case of the $2.99/ $3.00 item). Somehow the 99-price ending was distorting participants’ cost estimates. Remember also that some participants were asked to “think quickly” and others to “think carefully”. This made a difference, such that the tendency to overestimate how many items could be bought for $73 was more pronounced in the participants that were asked to think quickly.

How can these findings be explained? Well, the second study was carried out with a mixed gender group of university students and they were fooled by 99-ending prices. On that basis the 99 trick does not seem to be related to gender or lack of education. However, people were more prone to be fooled by 99-ending prices for purchases made without a good deal of thought.

In terms of how the 99 “trick” works, there are two psychological theories. The “underestimation” theory holds that we tend to pay more attention to the left-most figure of a price, so £1.99 looks like one pound, whereas £2.00 looks like, well, two pounds. There is some support from this in an analysis of the size of error made in the second experiment. The size of error was more often within 99 cents of the actual price when prices ended with 99, compared with when prices ended with 00. This magnitude of error is consistent with seeing $2.99 as $2.00.

The second psychological theory is that of “association”. The idea here is that 99-ending prices are associated with bargains, for example as would be found in a discount sale. Therefore, when we see a 99-ending price we think about discounts at some abstract level and this sways us towards the belief that the item is more of a bargain than it actually is. This idea was not scientifically tested in either study but it may contribute to the 99-ending price effect.

These studies are a welcome addition to the cool psychology blog. I’ve lost count of the number of times I’ve looked at items in shops priced at something-99 and thought: People don’t fall for that, do they? I’m sure many other people have too. Well, these psychology experiments answer that question. Ending prices in 99 is a marketing technique designed to make us buy more stuff. And what’s more, the studies I’ve reported here demonstrate that it works.

What can we do with this information? The second study showed that people are more prone to be fooled by 99-ending prices when not thinking carefully. So, weighing up purchases and trying not to buy items on impulse should help us avoid being fooled. But it’s probably not that easy. As people we are prone to the trials and stresses of life and there will be times when we have to make purchase decisions while stressed and thinking less carefully. Be aware that under these circumstances we may be more prone to the 99 trick. There is also the idea of “retail therapy” when people use shopping to try and boost mood. Might we be more prone to 99-ending pricing under these circumstances? I bet.

The references and links to the full papers describing these studies are included below. You can read the abstracts (a short summary) of the articles online for free by clicking on the links. There is a charge for obtaining the full papers unless you are able to access a library at a university or hospital with a subscription to the two journals that published the studies: Psychology and Marketing and Journal of Retailing. Otherwise you could try e-mailing the lead author, Professor of Marketing Robert Schindler and ask very politely for a pdf copy.

References

Bizer, G. Y., & Schindler, R. M. (2005). Direct evidence of ending-digit drop-off in price information processing. Psychology and Marketing, 22, 771-783. Link

Schindler, R. M., & Kibarian, P. N. (1996). Increased consumer sales response though use of 99-ending prices. Journal of Retailing, 72, 187-199. Link

Is love a drug?

The heady rush of intense romantic love is, perhaps, a defining aspect of what is to be a human being. Psychologists named this feeling “limerance” in the 1970s, and by the 1980s they were measuring it using questionnaires with exciting sounding names like the “Passionate Love Scale”. Still, the 2000s arrived and several important psychological questions around the nature of romantic love still remained unanswered. Should love best be thought of as an emotion in its own right? What is the relationship between romantic love and sex? And is love really a drug, as Roxy Music suggested in their 1975 hit single?

In 2005, psychologist Arthur Aron and his colleagues decided to delve into these interesting issues. 17 young men and women who had recently fallen in love and were in a relationship responded to a newspaper advertisement. Each provided a photograph of their beloved and, to provide a point of comparison, a second photograph portraying a friend of the same age and sex. One by one, the volunteers were inserted, torpedo-like, into an fMRI machine. Magnetic resonance imaging (MRI) uses magnetization of atoms in the body to create images of the brain and other internal organs. Functional MRI (fMRI) is a further refinement that can measure changing activity over time by detecting increased amounts of oxygen in the blood.

While having their brains scanned the volunteers viewed their photographs through an angled mirror. The researchers compared the brain scan images showing parts of the brain “lighting up” for the beloveds’ photographs with the friends’ photographs. This showed which brain regions became active in response to intense romantic love, over and above friendship. The findings were intriguing.

Romantic love activated a number of well-known emotional areas of the brain, namely the caudate nucleus, ventral tegmental area, insular cortex and cingulate cortex. There was no evidence of any specialised or unique brain system for love, which tells us that love is probably not an individual emotion in its own right. Instead, romantic love is better thought of as an accumulation of motivations and emotions, described by the researchers as a “goal-directed emotional state”. In other words, love is a mind-set that causes the experience of other more fundamental emotions like euphoria. This makes sense from an evolutionary perspective; romantic love directs us towards the goal of obtaining a partner for reproductive purposes, and finding one’s partner is rewarded by feelings of extreme emotional pleasure. Having said that, next time you are smooching your lover, choose you words carefully. Whispering how intense a goal-directed emotional state they set-off in you isn’t particularly romantic!

Recording activation in the caudate nucleus and ventral tegmental areas of the brain is interesting because these are key parts of the brain’s reward pathways. These pathways respond to pleasurable stimuli like eating chocolate, receiving money or experiencing an intense “high” from drugs like cocaine. The objective demonstration of activation of the brain’s same reward pathways by romantic love and drugs provides a scientific backing for the poetic idea of love being a very potent drug. Bryan Ferry was right!

And what of the age-old question of the relationship between love and sex? On the whole, the brain areas activated by romantic love were different to those activated during sexual arousal. We know this thanks to a 2002 study of 14 young men asked to watch an erotic video while undergoing an fMRI scan. At the same time, a strategically positioned electrical “cuff” verified physical signs of sexual arousal. The brain areas activated were the visual areas, the insula, the temporal and cingulate gyri, the caudate and the putamen. Because the brain regions activated for romantic love and sexual arousal were different, this shows that love and sex are distinct entities. More profoundly, the findings provide a scientific validation for the feeling of sexual desire in the absence of romantic love, otherwise known as “lust”. 

Rarely does one scientific study shine a light on so many quintessential issues. The patterns of brain activation in lovers viewing pictures of their darlings validate the lyrical concept of love being like a drug. In so doing, they underline the powerful hold romantic love can exert on people. Considering love as apart from lust informs how, as people age and sexual activity lessens, fulfilling long-term romantic relationships still evolve and thrive. Coming to think of romantic love not as one single emotion but as an accumulation of motivations and emotions provides insights into the complexity of love and hints at why humans remain inherently fascinated by it. This fascination is reflected in the portrayal of romantic love in music and the arts since time immemorial. And now, at last, science has joined the party.

The reference to the full paper describing this study is included below. If you access it from a library that subscribes to the journal you will be able to download the pdf file containing the article for free. If not, the link contains an e-mail address for one of the authors, Lucy L Brown. If you contact Dr Brown and ask very politely I’m sure she would send you a pdf copy of the paper for free.

Arthur Aron, Helen Fisher, Debra J. Mashek, Greg Strong, Haifang Li and Lucy L. Brown (2005). Reward, Motivation, and Emotion Systems Associated With Early-Stage Intense Romantic Love. Journal of Neurophysiology 94, 327-337. Link.

What does it feel like to die?

In March 2012 the Bolton Wanderers Football Club midfielder Fabrice Muamba collapsed on the field of play in a Premier League match against Tottenham Hotspur. He had suffered a heart attack and although he was apparently dead with no vital signs for a considerable length of time, he survived. In fact, he made a rapid recovery and was discharged from hospital a month later. The only sour note in what has been a remarkable return to health is the recent announcement of his enforced retirement from professional football.

As for the incident itself, Fabrice Muamba is on record describing his impressions of what happened. At first he felt a surreal dizziness as though he was running along inside someone else's body. The last thing he remembers is seeing two of the Tottenham player Scott Parker. Interestingly, he reports no feeling of pain as the cardiac arrest occurred and unconsciousness took hold.

I can't be the only football fan whose initial empathy for Fabrice Muamba and his family was the starting point for a deeper reflection upon the episode. Obviously, it is shocking that this could happen to a fit young 23 year old professional sports person. But beyond that, it certainly put my own mortality into sharp perspective. Or put bluntly, it made me think about my future death. When will it come? (Hopefully not for many years!) What will be its circumstances? (Peaceful, I hope!). And very simply - what does it feel like to die?

Death is a fundamental issue for human beings. We are unique amongst all the creatures on earth in having the cognitive capacity to possess the knowledge that one day we will die. This means that we have to come to terms with our deaths as we go about our lives. I am not an acquaintance of Fabrice Muamba and so I can't ask him about his experiences first hand. Yet I have no doubt that doing so would provide insights that would be useful in helping me to better come to terms with death.

However, as a psychologist, I do have access to the vast library of psychological research that has been carried out on many and varied topics. Though rare, cases of succesful resuscitation following protracted periods of clinical death, where a patient’s breathing and heart beat stop, do occasionally happen. One morning I decided to search the psychological research database to see what studies had been carried out with such survivors. One particular paper caught my eye for the Cool Psychology blog.

Around the turn of the millennium, Sam Parnia and his colleagues at Southampton General Hospital in the south of England approached all the patients in the hospital that been resuscitated following a heart attack in one year. These patients could easily be identified thanks to the telephone switchboard operators who routinely log all resuscitations as they are called in through the hospital's emergency phone system. There were 63 such patients and they were all interviewed. This group was ideal to form the basis of the study because cardiac arrest patients exhibit two out of the three criteria required to pronounce an individual dead - absence of cardiac output (no heartbeat), and absence of respiratory effort (not breathing). In fact many also exhibit the third criterion of fixed dilated pupils.

The research was in three parts. In the first part, each patient was simply asked whether they had any memories from when they were unconscious following their heart attack, and if so to recount them as clearly as possible. They found that seven individuals could recall their thoughts during the time they were unconscious, which is eleven per cent of the full group.

"Near Death Experience" is a recognised syndrome comprising of a specific pattern of thoughts and memories experienced during an episode of clinical death. A scoring system exists for classifying near death experience. Known as the "Greyson Scale", it consists of a list of consistently reported near death experiences including, among others, feeling time speed up or slow down, recalling scenes from the past, feelings of peace and harmony with the universe. This first part of the Southampton research aimed to distinguish between true near death experience and more random thoughts and memories during the unconsciousness. The Greyson scale was used to assign a score to the experiences recounted by each participant - the more experiences on the scale that are recounted, the higher the given score.

The Southampton patient group recounted several experiences during their unconsciousness. They remembered coming to a point or border of no return, feelings of peace, pleasantness and joy, heightened sensual awareness and a feeling of time speeding up. Four of the patients were classified as having had a true near death experience. Two others remembered some details commonly encountered during near death experience but not quite enough to be classified in the first group. The other patient recalled a less typical experience of people jumping off a mountain.

One of the classic near death experiences reported previously is the sensation of looking down at oneself from a viewpoint close to the ceiling. This is known technically as an "out of body experience". The second part of the study assessed out of body experiences in a very simple yet very clever (and really cool) way. The researchers suspended boards from the ceilings of all of the wards in the hospital. These boards had writing and figures drawn on their upper sides that would only be visible from a vantage point near the ceiling. Therefore, any participants reporting an out of body experience could reasonably be asked to describe what they saw on the upper sides of the boards as a test of whether their experience was real or imagined.

That seems to me to be an astonishing amount of trouble to have gone to in order to investigate this phenomenon. But, still, it perfectly captures the true essence of what science is - using logical tests to gather evidence as to whether some phenomenon is true or not. Science is not all about lab coats, high tech gadgets and undecipherable equations. These investigators simply and elegantly used very low-tech painted boards to set about gathering evidence for out of body experiences.

Unfortunately, though, despite having gone to all the trouble of installing these aids, none of the seven patients with memories from their period of unconsciousness reported viewing themselves from above. Therefore, sadly, this unsophisticated but ingenious research technique could not properly be put to use in the study.

The third part of the study aimed to find out whether the body's physiological state during cardiac arrest had any bearing on the patients being able to remember their thoughts while they were unconscious. The researchers were allowed access to the patients' medical notes and these recorded the levels of oxygen, sodium and potassium in the blood during the resuscitation. To try and tease apart how these may have been affecting the patients the study drew a comparison between the four patients that were classified as having had a true near death experience, and the 59 remaining patients in the study that did not. There was one very interesting difference between the two groups - blood oxygen levels were higher in the near death experience group of patients.

This is intriguing because one of the leading theories of near death experience at the time was that feelings such as heightened sensual awareness and time speeding up came about due to a lack of oxygen in the brain. It was thought that these phenomena occurred as the brain was starved of oxygen. The Southampton study instead suggests that rather than a lack of oxygen, it is the opposite, an availability of brain oxygen that seems necessary for a vivid near death experience. There is a logic to this because better brain oxygenation would allow for improved cognitive function during the resuscitation, which would explain the more vivid experience and the ability to commit it to memory.

What a wonderful piece of research. This paper is a worthy addition to the Cool Psychology blog because it has an elegance of design that is to be admired. Following up all the cardiac arrest sufferers at the hospital provides an insight into what proportion of people will likely experience conscious thought in the moments leading up to death - around ten per cent. It was certainly innovative to collect physiological information as well as the interview responses. Thanks to that we know that high blood oxygen levels during cardiac arrest are probably required to support a level of brain activity sufficient to register and form memories during the experience. But it was an inspired idea to fix message boards just below ceiling height to seek evidence for out of body experience. It was just unfortunate that none of the patients had an out of body experience, and so nothing can be learned from this highly original approach.

The paper is doubly welcome in the Cool Psychology blog because it gives some very well founded insights into an under-researched but fundamental human question: What does it feel like to die? Fascinatingly, cardiac arrest appears not to be traumatic - of those patients that could remember the experience at all, none reported it as unpleasant or painful. Moreover, memories that could be recalled point to a joyful, peaceful experience accompanied by a pleasantly heightened sensual awareness. These findings chime with Fabrice Muamba's re-telling of his experiences during a prolonged cardiac arrest. He said that he felt no pain whatsoever - just an odd, difficult to explain feeling.

So, what does it feel like to die? On this evidence, death by cardiac arrest seems to feel either like nothing, or something pleasant and perhaps slightly mystical. There was no evidence that having a cardiac arrest is painful. How reassuring. I take comfort from the notion that death may not necessarily be something to be feared. This being the case I think we can all rest easier as we carry on our lives in death's ever present, if perhaps now slightly fainter shadow.

The reference and a link to the full paper describing this study is included below. This paper was published in the peer review academic journal named Resuscitation. You can read the abstract (a short summary) of the article online for free by clicking on this link. There is a charge for obtaining the full paper unless you are able to access a library at a university or hospital with a subscription to the journal. Otherwise you could try e-mailing the lead author, Sam Parnia and ask very politely for a pdf copy.

Parnia, S, Waller, DG, Yeates, R, Fenwick, P (2001). A qualitative and quantitative study of the incidence, features and aetiology of near death experiences in cardiac arrest survivors. Resuscitation, 48, 149-156. Link

Sun, sea, shakes

Sunny Beach on the Black Sea is the largest beach resort in Bulgaria. Marketed as “the sunniest resort for the sunniest people”, it attracts many thousands of tourists each year who flock there to relax and enjoy the sandy beach and nightlife. Particularly, the nightlife. With its numerous pubs, bars, clubs, cafes and discos, Sunny Beach visitors regularly drink to excess in pursuit of party fun. There is, of course, a downside to this kind of behaviour. By the next morning the highs of the alcohol-fuelled bender give way to the lows of the alcohol hangover. I could try and put into words what a hangover feels like but I don’t need to because the author Kingsley Amis has already done so to great effect in his 1953 novel “Lucky Jim”. The novel’s main character awakens to find: “A dusty thudding in his head made the scene before him beat like a pulse. His mouth had been used as a latrine by some small creature of the night and then as its mausoleum… He resolved, having done it once, never to move his eyeballs again.”

The symptoms of alcohol hangover will be familiar to many readers of the cool psychology blog. Raging thirst, headache, feeling ill and being unable to stomach food are its hallmarks. Still, a scientific understanding of the alcohol hangover is in its infancy compared with alcohol research more generally. We know lots about alcohol intoxication effects that occur while alcohol is being carried around the body in the blood, and we also know a good deal about the more long-term effects associated with alcoholism. Alcohol hangover, on the other hand, has been very much neglected as a topic of serious scientific study, which is odd given that hangovers make up one of the key constituents of any drinking binge.

This is now beginning to change and there are two broad approaches used to research the alcohol hangover. In laboratory studies a controlled quantity of alcohol is consumed and effects several hours later are monitored. Unfortunately, in order to protect the health of the volunteers taking part, the amount of alcohol allowed in laboratory studies is strictly limited to no more than the equivalent of 6-7 bottles of beer. Because of this, the more “full blown” hangover effects arising from extensive alcohol consumption cannot properly be studied under laboratory conditions. An alternative approach is known as the “naturalistic” study. This entails interviewing drinkers the morning after they themselves have chosen to go on a boozing session often electing to consume much higher quantities of alcohol than would be allowed in the lab. Morten Hesse and Sebastien Tutenges of the Centre for Alcohol and Drug Research at the University of Aarhus in Copenhagen realised that Sunny Beach, being a place where numerous holiday makers consume astonishing amounts of alcohol, is the perfect venue to carry out a naturalistic study of alcohol hangover.

In the name of science four lucky researchers were dispatched to the resort one summer. Each morning they visited hotel swimming pools and beaches to meet Danish tourists aged 16-25. Over the course of one week they asked 76 male and 36 female holidaymakers to describe their nights out, alcohol consumption and alcohol hangover symptoms. Mornings were chosen because this is when hangover effects would be at their most severe. Each person was spoken to three times - after their first night out at Sunny Beach, after their third evening sampling the resort nightlife, and on the final day of their vacation. In most cases this was after their fifth sojourn to the pubs and clubs of the Black Sea holiday destination.

There was a good reason for repeatedly questioning the same individuals. The researchers wanted to try something unique in the field of alcohol hangover research – to be able to chart how hangovers progress over time in the face of continued drinking. It is possible that a tolerance would develop, such that hangovers would become less severe with each passing day. We are all familiar with the idea of tolerance to alcohol – but how would this play out with respect to alcohol hangover? On the other hand, rather than tolerance, perhaps hangovers would become progressively worse over the week-long holiday. This would be related to the idea that hangover is an “opponent process” to excessive alcohol consumption. Opponent processes encourage our bodies to take action against harmful exposures to things like drugs and toxins (such as excessive alcohol) with the aim of reducing those exposures. If hangover represents an opponent process to alcohol, then hangover severity should worsen upon repeated consumption of alcohol, as our bodies seek to reduce the amount of alcohol consumed.

A simple questionnaire called the Acute Hangover Scale was used to measure hangover. This asks you to rate hangover symptoms on a scale of 0 (none) to 8 (incapacitating). The symptoms they were asked to rate were: hangover, thirsty, tired, headache, dizziness, nausea, stomach-ache, heart racing and loss of appetite. Each Danish vacationer was asked to rate “how you feel right now”. The answer in most cases would have been something akin to “awful” because they were mostly suffering from a hangover at the time of asking. So in this environment of sun, sea, sand and alcohol-fuelled partying, how did hangover severity change during the week?

First, I should say that alcohol consumption decreased from the first to the final night out, although it remained overall quite high, at 17 standard units of alcohol on average each night. This is like drinking 10 bottles of Budweiser beer. Still, despite alcohol consumption reducing over the holiday, for most people, hangover severity increased over the week. In other words, the average hangover rating rose at each interview. This is the opposite of what we would have expected to see if there was such a thing as hangover tolerance, which is the idea that we can “get used” to hangovers so that we gradually feel them less strongly. Hangovers getting worse over the duration of the holiday favours instead the “opponent process” idea of hangover being the body’s response of preserving itself from harm by reducing the appetite for further intake of toxins like alcohol. An intriguing finding.

They also questioned whether women experience more severe hangovers than men, and whether age has any impact on alcohol hangover. They found that women’s hangovers were less severe than men’s, or at least so it seemed at first when responses on the hangover symptom scale were compared across men and women. However, closer scrutiny revealed that there was an obvious underlying reason why women’s hangovers were less severe than men’s - because the women tended to drink less than the men. There turned out to be no difference between men’s and women’s level of hangover symptoms when the amount of alcohol consumed was taken into account.

Interestingly hangover symptoms were less severe in the older people that were questioned (but remember that these “older” people were still in just in their 20s). The paper offers no proper explanation for why this might be and it wasn’t simply the case that the older individuals drank less – they didn’t . I have two suggestions. Perhaps as we get older, those people who most suffer from hangovers decide that drinking alcohol isn’t really for them and so they choose not to go on boozy beach holidays. If so, then the older people questioned in the study might seem to be more “hangover tolerant” than the younger ones solely because a proportion of non-tolerant older people would have been holidaying somewhere other than Sunny Beach. The older people at Sunny Beach would be what psychologists would call a “biased sample”. Allied to this, it is also possible that as they get older people learn strategies to avoid hangovers while continuing to drink excessively. There are many remedies for hangovers in circulation, but only a few have been researched properly. Perhaps hangover remedies could be a topic for a future cool psychology blog.

One fascinating conclusion from this study was whether some people are immune to hangover. To answer this, the investigators first had to come up with a definition of hangover based on responses on the Acute Hangover Scale. (If you think about it, just taking any score above zero as indicating a hangover would be inappropriate because we might all tick one or two boxes on the hangover scale on any given day just because of minor ailments like headache – but this doesn’t mean we have a hangover.) First they thought about how much alcohol would need to be consumed so that most people would have a hangover the next day. They decided on 12 or more units (equivalent to around 7 bottles of Budweiser beer). 79 of the study participants had consumed this amount or more on at least one night of the holiday and they were classed as heavy drinkers. The remaining 33 participants were classed as moderate drinkers who mostly reported just a few symptoms, if any. They defined hangover as an Acute Hangover Scale score high enough so that only a small number (10%) of moderate drinkers experienced it. Using this definition they found that only around two-thirds (68%) of the heavy drinkers actually experienced a hangover. This suggests that around one-third of people are immune from hangovers.

The Sunny Beach hangover study is a worthy addition to the cool psychology blog. For a start, how cool is it for researchers to fly to a beach holiday resort in order to collect their data? Why didn’t I think of that? Also, like other studies in the cool psychology blog, it used a very simple and direct approach – they wanted to study hangover so they went to a place where there are lots of hungover people. The findings too are very easy to understand and apply to everyday life. Women don’t necessarily have less severe hangovers than men – they just drink less. Hangovers don’t ease over time – if anything they get worse. And some people, around a third of heavy drinkers, are more or less immune from getting hangovers at all. Are they lucky? In some ways yes, since they can drink to excess and get off lightly the next day. However, without the “opponent process” or natural curb to excessive drinking that hangover provides, perhaps such individuals are more at risk from developing harmful patterns of alcohol consumption storing up possible health problems as they get older. Now there’s a sobering thought.

The reference and a link to the full paper describing this study is included below. This paper was published in the journal Addiction. At the time of writing I was able to download this article for free from the journal’s website.

Hesse, M & Tutenges, S (2010). Predictors of hangover during a week of heavy drinking on holiday. Addiction, 105(3), 476–483. DOI: 10.1111/j.1360-0443.2009.02816.x. Link

When Statistics Met Poohsticks

This blog follows a slightly different format to previous entries. Rather than review an interesting psychology study I offer something a little different, but still strongly themed by my day job of doing psychology research…

Chapter 6 of AA Milne’s “The House at Pooh Corner” introduces the now famous game of Poohsticks. The story goes that Winnie the Pooh invents the game after accidentally dropping a pine cone off a bridge into a flowing river. Having chanced upon the observation that a cone dropped over one side of the bridge will be carried by the current of the water passing beneath to the other side of the bridge, Pooh’s first thought is whether this might be what scientists would call a replicable phenomenon, or in everyday speak, something that can be repeated. He says: “That’s funny… I dropped it on the other side… and it came out on this side! I wonder if it would do it again?”. For a character based on a soft toy, Pooh bear has a remarkably scientific outlook on life!

He tries this several times and then by and by develops the game into a race by dropping two cones at once and trying to guess which will emerge on the other side of the bridge first as the race winner. When it was time to leave to go home for tea Pooh had won, by guessing the first cone correctly, 36 times, but lost 28 times. Milne suggests that this means that Pooh was – well, actually, the narrative stops short of making any kind of judgement as to Pooh’s predictive abilities. Milne explains it by saying that Pooh was: “well, you take twenty-eight from thirty-six, and that’s what he was”.

I was reading this story to my daughter at bedtime, and upon seeing this set of scores, the psychologist-statistician in me rather came to the fore. There is a statistical test of whether that distribution of scores – 36 correct and 28 incorrect – is likely to be due to chance, or not. If performance were at chance level, then this would suggest that Pooh was really only guessing which cone emerged from under the bridge first. The alternative possibility is that this number of correct predictions would be unlikely to be due to chance. In that case one could argue that Winnie the Pooh was applying some logic or skill of judgement in order to make consistently correct, above chance level predictions on the outcomes of Poohstick races. So, the first thing I did this morning was run the test and see!

The statistical test in question is called the “Chi-Square Goodness of Fit Test” (“chi” is pronounced like “sky” without the “s”). You can look up a technical description of it on Wikipedia, but I’ll try and provide a more straightforward description here.

It works by comparing real-life scores or data (here it is Pooh’s tally of Poohstick race results) with perfect 50-50 chance level of performance. In the case of Poohsticks, for a score of 36 vs. 28 there must have been 64 races in total (36 + 24 = 64). For 64 Poohstick races, the perfect 50-50 chance level of performance is 32 guessed correctly and 32 guessed incorrectly. The chi-square test helps us to decide what we should make of a change of 4 either side of that (32 – 4 = 28 and 32 + 4 = 36). There are two possible outcomes – probably chance level of performance (consistent with guessing) or probably non-chance level of performance (consistent with applying skill and judgement).

The crucial thing that enables a decision to be made about chance or non-chance performance is that someone, somewhere made very many observations of what happens over a series of chance level 50-50 calls. Perhaps they tossed a coin very many times, each time guessing first whether heads or tails would come up, and keeping a tally of whether they were right or wrong each time. In doing this they were mapping and defining the chance level of performance. Knowing what happens by chance helps us to decide whether a new set of scores resembles chance, or something else. The decision rests on the size of the difference between the correct and incorrect calls. Differences so large that they only occur 5% of the time under chance conditions are deemed to be “statistically significant”. Such differences are usually understood to be unlikely to be due to chance, and so likely to be due to some kind of phenomenon, such as, in this example, skill at Poohsticks.

So which was it for Winnie the Pooh’s first ever set of Poohsticks scores? I ran the analysis using the computer software SPSS^©. The chi-squared goodness of fit test showed that there was no significant effect, chi-square = 1.000, df = 1, p = 0.317. (NB In that last sentence I have reported the chi-squared test statistics in the same way that scientists would do in a research paper; “df” stands for degrees of freedom, and “p” stands for “probability”.) No effect means that Pooh was operating at chance level of performance. This tells us that anyone could obtain a score of 36 correct predictions and 28 incorrect predictions just by guessing the outcome of a series of Poohsticks races without using any skill or judgement.

Based on his original Poohsticks predictions you could argue that there is no evidence of Winnie the Pooh being anything other than a Bear of Very Little Brain. But let’s cut him some slack – he did invent the stillpopular pursuit of dropping cones and twigs into water on one side of a bridge before dashing across to watch them emerge on the other side. Poohsticks is a wonderful pastime in itself regardless of whether one can guess in what order they will appear. But just for the competitively minded out there – you would need to be correct in at least 40 out of 64 Poohsticks races in order for the chi-square test to return a significant result. Better get practising!

Post script
I posted the above on 2 July 2012. Today, 6th June 2013 a contributor, Eric, points out that I was not the first person to whom the idea of performing a chi-square on Winnie the Pooh's performance at Pooh sticks occurred! Click here for an article in the journal "Teaching Statistics" by Eric D. Nordmoe which preceeds my effort by 8 years! Apologies, Eric.

Towards a scientific understanding of time travel

We've all done this. You are sitting on a train in a station, and as the train begins to move you look out of the window and watch as you pass by an adjacent stationary train. Suddenly you become aware that you were mistaken. You realise that, in fact, your train is the one that is stationary and the adjacent train is the one that has started to pull out from the platform. Still, for a moment there your eyes fooled you into thinking that you were on the move. This all goes to show how visual information can be deceptive to the point of providing quite compelling sensations of non-existent movement.

This visual illusion was recently used by psychologists at Aberdeen University lead by Neil Macrae in a study investigating the psychology of time travel. Had you heard that time travel is now possible and has become an area for psychological research? Well, not actual time travel, but rather, mental time travel. In other words, how we think about things that happened in the past and how we imagine things that may happen in the future. Mental time travel allows people to revisit past experiences, like that romantic first kiss, and pre-experience the future, like looking forward to a hot cup of tea during a strenuous walk on a cold day.

Psychological research of mental time travel has become something of a growth area, although still very little is known about how it works. Macrae and his colleagues wanted to find out if mental time travel is represented in the brain’s sensory-motor systems - in other words, the parts of the brain that control our muscles to enable us to move about. One such region, the cerebellum, is a curious part of the brain. It is named from the Latin for “little brain” because it is small (golf ball-sized) and because it sits almost like a second brain just below, and to the rear, of the two hemispheres that make up the bulk of the mass of the human brain.

The idea that thoughts and muscle control can be strongly related to one another has already been well-developed in another area of psychology research known as “muscle memory”. A good example of muscle memory is the fine control of movement needed to sprinkle sugar from a teaspoon. This skill has to be learned, and therefore it uses memory. However, the way the brain handles memories for how to use our muscles is different to other kinds of memory, such as memory for facts like naming the capital city of France. Muscle memories are represented in the parts of the brain that are associated with controlling bodily movement, such as the cerebellum. So, the question being asked in the paper is whether mental time travel is represented or connected with muscle memory.

Links between mental time travel and physical movement had already been established in previous research carried out by some of the same authors. In an earlier study they asked blindfolded participants to stand still and imagine the events of a typical day four years ago, or to envisage events of how a typical day might be in four years’ time. A device measured body sway while carrying out these tasks. Interestingly, they found that thinking about the past lead to more backwards sway, while thinking about the future lead to more forwards sway. This was a pretty cool finding and one that provides a basis for thinking that mental time travel may well involve muscle memory (because a consistent muscle movement was produced by one or other type of imagination task). But now the question was – having found that mental time travel can influence movement, was the reverse also true? Could movement, or at least apparent movement, be shown to influence the direction of mental time travel?

This brings us back to the train-movement illusion that I talked about in the opening lines of this blog entry. Psychologists prefer, if they can, to carry out research under the carefully controlled environment of a psychology laboratory rather than amid the noise and hullabaloo of everyday real-life settings. The thinking behind this is straightforward: by carefully controlling as many aspects of the immediate environment as possible, unwanted distractions can be minimized so that even very subtle effects can be observed. Now, in a laboratory, clearly the amount of movement that is possible is limited by the size of the space. To overcome this hurdle, rather than look at effects of actual movement, Macrae’s study used a computer graphics to create the illusion of movement.

You have probably seen the starfield animation being used as a screen saver on a personal computer. It consists of a black screen with small white dots randomly scattered across it, similar to the appearance of stars in the sky on a clear night. It can be animated in two directions. The stars can move from the centre outwards, inducing the feeling of forward motion, or conversely, they can move from the outside towards the centre, inducing the feeling of backwards movement. This was an ideal means of creating the illusion of forwards or backwards movement.

The final part of the experiment reflected the need to create suitable conditions so that the participants’ minds would wander and engage in mental time travel while viewing the starfield animation. For this, the 26 volunteers were asked to perform a very tedious and boring task of pressing the mouse button whenever the letter “O” appeared among the stars on the screen. To maximise boredom this only happened a few times during the 6 minute animation.

Afterwards the participants were asked whether they had experienced any daydreams while doing the task. If so, they were also asked what they had been daydreaming about and to estimate the proportion of daydreams that were related to past and future events. Only one individual said they had not had any daydreams. The others had all been daydreaming during the task as investigators hoped they would. They were mostly either reliving recent memories like what happened to whom on the last big night out, or perhaps imagining what they hoped they would be able to do over the coming days.

If you have read up to here you will appreciate that if mental time travel is connected with muscle memory then we would expect the forward star field animation to lead to more mental time travel into the future, and for the backward animation to produce more mental time travel into the past. This is exactly what was found. Forward movement produced 19% more mental time travel into the future than the past, while backwards movement produced 23% more mental time travel into the past than the future. A small effect, admittedly, but still one that was very unlikely to be due to chance according to the statistical analysis carried out.

While this time travel research is all very cool, certain aspects of the study are worth thinking about from different perspectives. Asking people to report their daydreams at the end of a period of time, rather than interrupting and asking people to report what their thoughts there and then, would have reduced how accurate the reports were. Why? Because it is well known that memory decays over time, so that people might not be very good at reporting 6 minutes worth of daydreaming all in one go. If this is true, it could be the reporting of the daydream content that is affected by the forwards and backwards movement, rather than the actual daydreams that were experienced. Repeating the study but asking people to report their daydreams as they happened rather than after 6 minutes would shed further light on how much of a problem this is.

There is also the problem of whether the notion of forwards leading to the future and backwards leading to the past is a universal human trait, or merely a convention. In fact, the authors mention certain South American indigenous peoples that have the opposite convention. Because human eyes point forwards, and because the past has already been seen, these people speak of the past as being in front. On the other hand, because behind is not seen, and because the future is not yet seen, these people speak of the future as being behind. There is a nice logic to this conceptualisation and it would be very interesting to repeat the study with participants who share this “reverse conventional” view of the position of the past and future, and ask about their mental time travel in response to the forwards and backwards animations.

Still, this is certainly a cool piece of psychological research on several levels. For a start, even the idea of researching time travel is ultra-cool. Nerdy, perhaps, but nerdy in a cool way. There is also a simplicity and elegance to the research design in terms of what it set out to find out and how it went about it. People sat in front of a computer and were asked about their daydreams. I’m a great admirer of simplicity and here is a case in point. Lastly, the findings are cool and something you can put to the test on your next journey. If you are facing an uncertain future, you might be best advised to sit facing forwards. This is likely to facilitate future-oriented daydreams that might improve your plans for how to deal with this impending uncertainty. On the other hand, if you are feeling like wallowing in nostalgia, or perhaps you want to try and conjure up some forgotten fact (where did you leave your keys?), then sitting facing rearward might just help you to relive those memories more vividly. So, board your train, choose a seat facing forward or backward as the mood takes you, and daydream the journey away. Bliss.

The reference and a link to the full paper describing this study is included below. This paper was published in the online journal PLoS ONE. Anyone can access PLoS ONE articles online for free.

Miles LK, Karpinska K, Lumsden J, Macrae CN (2010) The Meandering Mind: Vection and Mental Time Travel. PLoS ONE 5(5): e10825. doi:10.1371/journal.pone.0010825. Link