Although most animals are bilaterally symmetric, there are numerous subtle differences between left and right. An obvious example is that most humans prefer one hand, usually the right, over the other. Another famous example is the lateralization of most language functions to the left hemisphere of the brain.

Our perception of the world is not perfectly symmetrical either. In general we pay more attention to what happens to our right, but this preference is heavily dependent on context. When it comes to social interactions, we prefer the left visual field. For example, we tend to hold babies so that the baby faces us from the left.

Beluga mother and calf (Source: Wikimedia Commons)

This left-side preference in social interactions is not limited to humans. Chicks, for example, prefer to view other familiar chicks with their left eye (they also peck more at other chicks if they approach from the left - a social interaction, but not a very friendly one). And in a recent paper in PLoS One, Karenina and colleagues show that baby Beluga whales prefer to swim on their mothers right side, presumably so the baby can view its mother with its left eye. You might wonder if it's not the other way around, so that the mothers prefer to view the babies with their right eye, but apparently this is not the case. The mother whales are pretty much just floating around, and the babies control most of the interactions. Call me soft, but I think this is …

A big problem in psychological experiments is that the stimulus material is generally not very realistic. (For example, what do smileys really tell us about processing of emotional expressions?) This problem plagues my experiments as much as anybody else's. Therefore, in an attempt to add some extra realism to my stimuli I created anaglyphs today. Anaglyphs are images that convey a sense of 3d when viewed with red/blue (or sometimes red/ green) glasses. I'm not entirely sure yet if anaglyphs are suitable stimulus material, because they can be a little hard to view (they tend to look out-of-focus). But I guess I'll find out!

Here is a short video of the set-up that I used for creating the anaglyphs.

Update Nov 4 2010: After reading some more about the immaculate conception, I learned that it is actually not the same as the virgin birth of Jesus according to Christian doctrine. So the title of this post is somewhat misleading, for which my apologies.

Parthenogenesis, usually called immaculate conception when it occurs in humans, is a type of asexual reproduction. Many invertebrate species do it and cases of facultative (i.e., without human intervention) parthenogenesis in vertrebrates have been reported as well. In a forthcoming paper in Biology Letters, Booth and colleagues describe a case of parthenogenesis in the Boa constrictor. Apparently, this is the first time that parthenogenesis in Boa constrictors has been shown to produce viable offspring.

Source: Wikimedia Commons

The baby snakes are a little “off”, though. In Boa constrictors (and in many other species, including birds), females are heterogametic, which means that they have two different sex chromosomes (ZW). Male snakes are homogametic, having two of the same sex chromosomes (ZZ). (Note that it is the other way around in mammals, in which the males are heterogametic (XY) and the females homogametic (XX).) The asexually reproduced snakes are female, but not of the ordinary type, since they carry two WW chromosomes. The authors are puzzled by the lack of males (ZZ) in the litter and suggest that the mother snake may have been a genetic freak, lacking a Z chromosome.

References

I know it's lame to pick out unfortunate sentences (I know I've written my share too. For example, I initially misspelled the names of both Oliver Sacks and Victor Lamme in my reviews of their books.), but I just couldn't resist reproducing this one:

“If you were to pick up and dissect any living organism from anywhere around the globe, you would undoubtedly find at least one other species inside of it.”

Apparently, there is some kind of weird recursion going on, with organisms being parasites of their own parasites. A type of infinite Russian doll parasitism. Otherwise I would say that at most 50% of all living organism has another organism living inside of it.

This sentence was taken from a review of the book “What's Eating You?” by Eugene Kaplan. Which, by the way, seems like a very interesting book.

Image from Wikimedia Commons

References

People rely on space to represent all types of essentially non-spatial things. For example, most people represent numbers in a spatial manner. Low numbers are pretty consistently associated with left, and right numbers... I'm sorry, high numbers are associated with right. This has been dubbed the mental number line.

You might wonder whether we have a similar representation of time. And indeed we do. Western people perceive time as flowing from left to right. This can be tested by having participants sort a set of cards, which depict some type of temporal progression. For example, participants might be asked to sort a set of photos showing a man of various ages. Sure enough, participants will layout the cards with the young man on the left and the old man on the right.

There is of course nothing inherently left about the past. Presumably, our tendency to associate the past with left stems from the fact that we write from left to right. This left-to-right bias simply transfers to other domains. In a forthcoming paper in Psychological Science, Boroditsky and Gaby show that people from Pormpuraaw, an aboriginal community in Australia, have a very different way of representing time. In the same card sorting-task, Pormpuraawans layout the cards from east to west. Boroditsky and Gaby tested this by having participants perform the task two times and rotating the experimental set-up for the second time. Western participants didn't care about the rotation. Without a compass, most of us are totally disoriented anyway …