Econstudentlog

Stuff

i. PlosOne: Underestimating Calorie Content When Healthy Foods Are Present: An Averaging Effect or a Reference-Dependent Anchoring Effect?

“Previous studies have shown that estimations of the calorie content of an unhealthy main meal food tend to be lower when the food is shown alongside a healthy item (e.g. fruit or vegetables) than when shown alone. This effect has been called the negative calorie illusion and has been attributed to averaging the unhealthy (vice) and healthy (virtue) foods leading to increased perceived healthiness and reduced calorie estimates. The current study aimed to replicate and extend these findings to test the hypothesized mediating effect of ratings of healthiness of foods on calorie estimates. […] The first two studies failed to replicate the negative calorie illusion. In a final study, the use of a reference food, closely following a procedure from a previously published study, did elicit a negative calorie illusion. No evidence was found for a mediating role of healthiness estimates. […] The negative calorie illusion appears to be a function of the contrast between a food being judged and a reference, supporting the hypothesis that the negative calorie illusion arises from the use of a reference-dependent anchoring and adjustment heuristic and not from an ‘averaging’ effect, as initially proposed. This finding is consistent with existing data on sequential calorie estimates, and highlights a significant impact of the order in which foods are viewed on how foods are evaluated.” […]

The basic idea behind the ‘averaging effect’ above is that your calorie estimate depends on how ‘healthy’ you assume the dish to be; the intuition here is that if you see an apple next to an icecream, you may think of the dish as more healthy than if the apple wasn’t there and that might lead to faulty (faultier) estimates of the actual number of calories in the dish (incidentally presumably such an effect is possible to detect even if people correctly infer that the latter dish has more calories than does the former; what’s of interest here is the estimate error, not the actual estimate). These guys have a hard time finding a negative calorie illusion at all (they don’t in the first two studies), and in the case where they do the mechanism is different from the one initially proposed; it seems to them that the story to be told is a story about anchoring effects. I like when replication attempts get published, especially when they fail to replicate – such studies are important. Here are a few more remarks from the study, about ‘real-world implications’:

“Calorie estimates are a simple measure of participant’s perception of foods; however they almost certainly do not reflect actual factual knowledge about a food’s calorie content. It is not currently known whether calorie estimates are related to the expected satiety for a food, or anticipated tastiness. The data from the current studies fail to show that calorie estimates are derived directly from the healthiness ratings of foods. Other studies have shown that calorie estimates are influenced by the restaurant from which a food is purchased [12], as well as the order in which foods are presented [current study, 11], very much supporting the contextually sensitive nature of calorie estimates. And there is some evidence that erroneous calorie estimates alter portion size selection [13] and that lower calorie estimates for a main meal item have been shown to alter selection for drinks and side dishes [12].

Based on the current data, a negative calorie illusion is unlikely to be driving systematic failures in calorie estimations when incidental “healthy foods”, such as fruit and vegetables, are viewed alongside energy dense nutrition poor foods in advertisements or food labels. Foods would need to be viewed in a pre-determined sequence for systematic errors in real-world instances of calorie estimates. A couple of examples when this might occur are when food items are viewed in a meal with courses (starter, main, dessert) or when foods are seen in a specified order as they are positioned on a food menu or within the pathway around a supermarket from the entrance to the checkout tills.”

ii. A couple of reddit book lists that may be of interest: AskHistorians book list. AskAnthropology reading list. I’ve added a couple of books from those lists to my to-read list.

iii. You can read some pages from Popper’s Conjectures and Refutations here. A few quotes:

“I found that those of my friends who were admirers of Marx, Freud, and Adler, were impressed by a number of points common to these theories, and especially by their apparent explanatory power. These theories appeared to be able to explain practically everything that happened within the fields to which they referred. The study of any of them seemed to have the effect of an intellectual conversion or revelation, opening your eyes to a new truth hidden from those not yet initiated. Once your eyes were thus opened you saw confirming instances everywhere: the world was full of verifications of the theory. Whatever happened always confirmed it. Thus its truth appeared manifest; and unbelievers were clearly people who did not want to see the manifest truth; who refused to see it, either because it was against their class interest, or because of their repressions which were still ʺun‐analysedʺ and crying aloud for treatment.

The most characteristic element in this situation seemed to me the incessant stream of confirmations, of observations which ʺverifiedʺ the theories in question; and this point was constantly emphasized by their adherents. A Marxist could not open a newspaper without finding on every page confirming evidence for his interpretation of history; not only in the news, but also in its presentation ‐ which revealed the class bias of the paper ‐ and especially of course in what the paper did not say. The Freudian analysts emphasized that their theories were constantly verified by their ʺclinical observations.” […] I could not think of any human behaviour which could not be interpreted in terms of either theory [Freud or Adler]. It was precisely this fact ‐ that they always fitted, that they were always confirmed ‐ which in the eyes of their admirers constituted the strongest argument in favour of these theories. It began to dawn on me that this apparent strength was in fact their weakness. […]

These considerations led me in the winter of 1919 ‐ 20 to conclusions which I may now reformulate as follows.
(1) It is easy to obtain confirmations, or verifications, for nearly every theory ‐ if we look for confirmations.
(2) Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory ‐ an event which would have refuted the theory.
(3) Every ʺgoodʺ scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.
(4) A theory which is not refutable by any conceivable event is nonscientific. Irrefutability is not a virtue of theory (as people often think) but a vice.
(5) Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability; some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks.
(6) Confirming evidence should not count except when it is the result of a genuine test of the theory; and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of ʺcorroborating evidence.ʺ)
(7) Some genuinely testable theories, when found to be false, are still upheld by their admirers ‐ for example by introducing ad hoc some auxiliary assumption, or by re‐interpreting theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later described such a rescuing operation as a ʺconventionalist twistʺ or a ʺconventionalist stratagem.ʺ)

One can sum up all this by saying that the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.”

iv. A couple of physics videos:

v. The hidden threat that could prevent Polio’s global eradication.

“Global eradication of polio has been the ultimate game of Whack-a-Mole for the past decade; when it seems the virus has been beaten into submission in a final refuge, up it pops in a new region. Now, as vanquishing polio worldwide appears again within reach, another insidious threat may be in store from infection sources hidden in plain view.

Polio’s latest redoubts are “chronic excreters,” people with compromised immune systems who, having swallowed weakened polioviruses in an oral vaccine as children, generate and shed live viruses from their intestines and upper respiratory tracts for years. Healthy children react to the vaccine by developing antibodies that shut down viral replication, thus gaining immunity to infection. But chronic excreters cannot quite complete that process and instead churn out a steady supply of viruses. The oral vaccine’s weakened viruses can mutate and regain wild polio’s hallmark ability to paralyze the people it infects. After coming into wider awareness in the mid-1990s, the condition shocked researchers. […] Chronic excreters are generally only discovered when they develop polio after years of surreptitiously spreading the virus.”

Wikipedia incidentally has a featured article about Poliomyelitis here.

August 24, 2013 - Posted by | medicine, papers, philosophy, Physics, Psychology, random stuff, science

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