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 …

As you can see, cogsci.nl has received a minor revamp of the layout. In the end I thought the previous layout (especially the grey header) was a little boring. There are now several headers, each with its own distinct color, and one is selected at random when you load a page. You can find links to the photos that I used on the about page. I will probably create some more in the future, to add to the variety. Another change is the addition of Facebook and Twitter buttons below each article.

Picador, 2010

Conclusion With “The Mind's Eye” Oliver Sacks reaffirms his reputation as one of the most eloquent chroniclers of the human brain.

More than anything else, Oliver Sacks is a storyteller. In “The Mind's Eye” he tells about people who have lost some aspect of their perceptive (mostly vision) or expressive (mostly speech) abilities. The book opens with a woman who suffers from severe difficulties in reading. Over the course of years her condition deteriorates, until her visual agnosia is so bad that she is effectively blind. Sacks gives a very personal and compassionate account of her story (as he does of the other cases described in the book), and focuses on the womans personality and the way she tries to cope with her condition, as much as he does on the neurological aspects. Sacks is also very eloquent; Almost unrivaled in this respect, I would say.

Nevertheless, after the first three chapters I was getting a little worried that the entire book would consist of case studies. Not that the stories aren't interesting, just not sufficiently so to fill 250 pages, especially since similar stories have been told before. Luckily, my worries were unfounded and about halfway the book switches from case studies to Sacks' personal quirks, hobbies and experiences. Apparently, he suffers from congenital prosopagnosia, which means that he has a very hard time recognizing faces. He describes how this mild deficit has led to some embarrassing situations (quite amusing) and goes a little bit into the …