Words and Messages

Longer words carry more information, according to research by cognitive scientists. It might sound obvious, until you start to think about it. Why, then, the difference between short 'now' and long 'immediately'?

For many years, linguists have believed that the length of a word was associated with how often it was used, and that short words are used more frequently than long ones. It was believed that the relationship between word length and frequency of use was based on an impulse to minimize the time and effort needed for speaking and writing.

But Steven Piantadosi and colleagues at the Massachusetts Institute of Technology say that, to give information, it is more efficient to shorten the least informative words, not the most frequent ones. After analyzing word use in eleven different European languages, they found that word length was related with their information content, not with how often they are used.

Measuring the information of a word isn't easy, especially because it can vary depending on the context. The MIT group invented a method for estimating the information content of words in digitized texts by looking at how it is correlated with the preceding words.

But, why do scientists study this? Well, some linguists think language was not born to communicate; in fact, language is about establishing social relations. This study by the MIT is a ferocious counterattack by those who think languages are adapted to deliver information efficiently.

Extracted from an article by Philip Ball in Nature News. Picture by iStockphoto.com/Pgiam.

An Explanation for Mass Extinction

The Permian–Triassic extinction devastated life on Earth 250 million years ago: it killed 96% of marine species and 70% of land-based vertebrate organisms. The reason may have been a volcanic explosion in coal deposits in Siberia. Some days later, ash from the eruption, raining down onto the Canadian Arctic, sucked oxygen from the water and threw toxic elements.

Stephen Grasby, a geochemist, and his colleagues have found three distinct layers of coal ash -fine particles that are freed when coal burns- in rock sediments just before the Permian–Triassic extinction.

 Experts have said for years that volcanoes in Siberian were responsible for the extinction event. There, some rock formations were formed by volcanic activity occurring about the same time as the mass extinction. But with volcanic eruptions so common in history, extra factors must have been involved. In this case, about 500,000–750,000 years before the extinction event, magma went up underground and hit a coal deposit. The mix was explosive and broke the Earth's surface.

Studies have suggested the volcanoes released 3 trillion tonnes of carbon, enough to cause massive climate change. The eruptions also caused acid rain and created an ozone hole. Toxic ash may have been the final blow.

The discovery is so crucial that other studies of extinction events should be examined for the presence of ash.

Extracted from an article by Gayathri Vaidyanathan in Nature News.

Friends connect on a genetic level

Groups of friends show genetic similarity, according to a study that surveyed variation in two out of six genes sampled among friends and strangers. For some geneticists, the conclusion is difficult to believe, because the scientists have not analysed enough genes to be sure that other explanations are impossible.

James Fowler, a social scientist at the University of California, looked at the data on six genes from about 5,000 individuals, and recorded the variation at one specific point, or single nucleotide polymorphism (SNP), in each gene, and compared this between friends and non-friends.

After investigating genetic similarity due to sex, age, race or common ancestry, friends still used to have the same SNP at one position in a gene called DRD2. Friends also showed more variation at one position in the gene CYP2A6 than non-friends.

The ultimate function of DRD2 or CYP2A6 is not clear. But the authors point out that previous studies have associated both genes -controversially- with social behaviour: DRD2 with alcoholism and CYP2A6 with 'openness'. There might be an evolutionary benefit to having friends with compatible genes, even if you don't have children with them. For example, if people who are naturally less susceptible to bacterial infection meet together, their collective health as a group multiplies because the bacteria have no place to live in.

But not everyone is convinced. Because most genes have modest effects on behaviour or health, many scientists think that thousands of SNPs -not only six- need to be analysed before a correlation can be confidently made. 

Adapted from an article by Amy Maxmen in Nature News. Picture by Nana Taimour.

Female tears prevent sex in men.

Women's tears contain chemical signals that reduce testosterone levels in men, according to a study by a neuroscientist in Israel. Testosterone is a hormone found in mammals, reptiles and birds. It is the principal male sex hormone.

The existence of pheromones -chemical signals that produce a social response- in humans has been debated for a long time. Investigation has shown that human sweat communicates information about identity, genetic relatedness, emotional states and health status. Mouse tears contain sex pheromones, but scientists have not previously demonstrated that human crying is a form of chemical communication.

In the study, women watched sad films alone and captured their own tears. Later, 24 men smelled jars containing those women's tears or another substance. Men who sniffed tears judged pictures of women's faces to be less sexually attractive than did the other men. In a separate experiment, 50 men sniffed either tears or the second substance. Smelling tears reduced their sexual response and levels of testosterone in their saliva. The study also exposed 16 men to tears and measured their brain activity using magnetic resonance imaging. Men who sniffed tears showed lower activation in brain regions implicated in sexual arousal.

Robert Provine, who studies the evolution of behaviour at the University of Maryland, says that the results are consistent with previous suggestions that crying could reduce aggression. Testosterone is also responsible for hostility, and reducing aggression could be evolutionarily adaptive.

The results are fascinating. Perhaps more studies on the subject are needed.

Adapted from an article by Janelle Weaver in Nature News. Picture by Punchstock.

Vacunas por decreto

Vacunarse por orden judicial.

Si hacéis un tanteo entre gente menor de 20 años es bastante probable que la mayoría no sepa cuáles son los síntomas del sarampión. Los pocos que lo saben no pasarían la prueba de explicaros además qué ocurre cuando tienes parotiditis y que secuelas puede dejar la rubeola. No es que esta generación esté menos informada en cuestiones de salud que la generación de sus padres, sino que gracias a la vacunación generalizada no han tenido la experiencia de ver a nadie con este tipo de enfermedades infecciosas que antes eran más habituales y que se solucionan con dos dosis de la vacuna llamada triple vírica. Mientras la mayoría de la población esté vacunada el virus no tiene suficientes organismos donde hospedarse y reproducirse. Pero si en una zona concreta muchos padres deciden no vacunar a sus hijos, existe la posibilidad de que se produzca un nuevo brote de una de ellas, con mucha facilidad de sarampión pues es una de las enfermedades más contagiosas que existen.

Esto es lo que ha sucedido en un barrio de Granada, ante lo cual el juez ha decidido obligar- incluso usando la fuerza si fuera necesario- a los padres a vacunar a sus hijos por motivos de salud pública-para proteger a toda la comunidad-aunque sea en perjuicio de los derechos de este grupo de padres. Las asociaciones de vecinos advierten que mientras no se cumpla dicha orden muchas madres no se atreven a sacar a sus bebés de casa por miedo al contagio. Los padres objetores alegan motivos ideológicos y la posibilidad de acogerse a métodos naturales para reforzar el sistema inmunológico de sus hijos. Los médicos de la zona tratan de explicar a la población cuáles son las ventajas médicas de vacunarse, tanto a nivel individual como colectivo.
 
Cada grupo deberá representar uno de los roles y escribir un manifiesto como “comentario” en el blog, que después se expondrá en clase antes de empezar el debate.