Four articles this month. Three of them are about humans the last one, about giraffes, is just something I threw in for fun. The three articles about people deal respectively with yet another mooted cause for schizophrenia, how our sense of touch affects our judgment and an unconventional, but very intuitive, way of determining whether or not someone is lying.
Schizophrenia
The first article is from The Economist and deliberately evokes a scenario that could have come right out of Invasion of the Body Snatchers. There have been many different causes mooted for schizophrenia over the years and some of the theories I’ve read even include pathogens. But this is the first time I’ve heard that it’s caused by one that explicitly causes behavioral changes in its host to ensure its own propagation.
The pathogen in question is Toxoplasma gondii and in some parts of the world, up to 60% of the population may be infected with it. In most cases, infection doesn’t seem to cause serious symptoms but it does appear that higher infection levels are correlated with neurotic symptoms, including poor reaction times, short attention spans and outright schizophrenia. What is most interesting however is how it causes behavioral changes in the organisms that serve as its usual hosts: cats and rodents.
This is because the pathogen needs to live in different hosts according to the phases of its lifecycle. In cats, the mature organism resides in wall of the small intestine and is passed out with the feces of its host. This is then eaten by rats and other rodents and the pathogen then form cysts in the brains of the new hosts. Eventually, if the rodents are eaten by cats, the pathogen changes hosts again and the cycle begins anew.
In order to make it more likely that its rodent hosts do get eaten by cats, the pathogen makes biochemical changes in the brains of its hosts to influence their behavior. Rats and mice that are infected tend to wander around and draw attention to themselves so that cats are more apt to pursue them. This naturally is against the interests of the rats and mice, but very much in the interests of the Toxoplasma pathogen.
According to this theory, humans are accidental hosts and probably become infected when they ingest contaminated food. Infected humans can’t help the pathogen to reproduce but it does take up residence in the brains of people and may influence their behavior in odd ways. According to the scientists, this is what causes schizophrenia as well as a host of other neurotic behavior. It’s a far-fetched theory and one that is far from being proved true, but the biochemical evidence looks promising so far.
Embodied Cognition
The next article is about a series of psychological experiments by Joshua Ackerman of the Massachusetts Institute of Technology as highlighted in Discover. The point is to demonstrate how our sense of touch can influence our decision-making process. Each of these experiments require the participants to manipulate an object with specific properties in their hands. They are then given a task to perform which usually involves them assessing someone or something and it is then found that the properties of the object they’ve touched affects their assessment.
In one example, the participants were asked to interview candidates for a job using a clipboard provided by the team running the experiment. Some of the participants were given a heavy clipboard while others were given a lighter one. The study found that the volunteers who held the heavier board rated the same candidates more highly based on their resumes and judged that they were more serious about the application. However, the weight of the board did not affect the volunteers’ judgment on other matters, such as how social they thought the candidate would be.
Similarly when asked to assess how government funds should be spent, volunteers who were given heavier boards were more likely to allocate more money to areas deemed to be more serious, such as air pollution standards, rather than trivial ones such as public toilet regulations. What worked for weight, worked for texture as well. Negotiators who sat on softer, more comfortable chairs tended to be more easy-going and flexible while those who were given hard chairs to sit on would not change their decisions once they were made.
Ackerman explains that these effects are due to how deeply rooted abstract concepts are in physical sensations. This is similar to the ideas of Antonio Damasio about how thought itself is inextricably linked with the biological processes that take place in the human body. I suppose it amounts to yet another chip in the stone that we traditionally conceive of as free will.
Drawing Truth
Next up, we have an article that presents a novel, but in retrospect, painfully obvious method to divine whether or not someone is telling the truth. This was a post on the Research Digest Blog and is based on a study by Albert Vrij of the University of Portsmouth. Normally, when we question someone about an event that happened in the past, we rely on their answers, whether verbal or written, and try to work out its truthfulness by searching out contradictions in their statements. In practice, this can be very difficult as language is an imperfect method of describing a past event and you may need to ask a lot of questions and sift through a lot of answers to judge whether or not a statement is true.
Perhaps inspired by the dictum that a picture tells a thousand words, the study asked participants to describe a past events in drawings rather than words. The participants were all from the police and the military. They were given a mock mission in which the participant needed to pick up a package from another agent before delivering it somewhere else. Half of the participants were truth-tellers who actually did go through the mock mission. The other half were liars who did not perform the mission but were told to lie that they did.
Since the liars had not actually been to the location that the exchange took place, the researchers reasoned that they would to visualize a location known to them from memory and draw that instead. They also thought that when the liars did this, they would forget to include the other agent involved in the supposed exchange in their drawing. This proved to be true and the study found that 80% of the truth tellers and 87% of liars could be correctly determined based on this alone.
The researchers also found that depending on whether they were telling the truth or lying, the participants tended to present their drawings from different perspectives. 53% of the truth tellers chose to draw from a first person perspective and 47% chose a top-down, bird’s-eye view, but 81% of the liars went for the bird’s-eye view. This intuitively makes a lot of sense for me. If I were pretending to visualize a place I’ve never been before, I’d bet I’d have picked the more impersonal top-down view as well.
Flotation Dynamics
Finally the fun article is a whimsical examination on a question that must have vexed many people through the ages: can giraffes swim? The article in question is a post on ScienceBlogs and covers a bona fide paper published by Don Henderson and Darren Naish (who authored the post himself). The odd thing about giraffes is that while many observations have been of them crossing rivers and other bodies of water, it is not at all clear whether or not they are actually swimming or simply wading across. In one instance cited in the post, giraffes were observed trying to cross a river and then turning back at about the half-way point.
In an attempt to settle this question once and for all, the two authors created a digital model of a giraffe and dropped it into digital water. Particular attention was paid to two aspects of the digital model that would affect its buoyancy: density and the volume of the animal’s lungs. As a form of control, they also modeled a digital version of a horse to test the predictive ability of their model since data on how horses perform in water already exists.
Their conclusion is that giraffes can indeed float but would make for very poor swimmers due to the shape of their bodies in the water. Of course, the real test would still be closely observing them in the wild and this study makes for a good example of how conclusions can be reached using only digital models and plenty of computational power. Most interesting of all is what it tells us about the things that scientists get up to during their free time.