Mangarevan arithmetic

PNAS recently published a cognitive anthropology paper titled Mangarevan invention of binary steps for easier calculation. The paper describes an arithmetic system that had been used for hundreds of years by islanders living in Mangareva (a small island in French Polynesia) for the purpose of “counting a small group of highly valued objects such as turtles, fish, coconuts, octopuses, and breadfruits”. This system is not too different from the decimal system that we’re using today, except that a number in the Mangarevan language can contain a small segment of binary code, which employs four numerals to represent 10 multiplied by the first four powers of 2.
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A historical note about color vision

What was the first time that we know that non-human animals have color vision? From what I can find, the first person who scientifically came to that conclusion was John Lubbock in 1888. What was so strange about it was that he studied Daphnia - a plankton (!). He discovered that the plankton was attracted to yellow light, but not to white light. Lubbock also reasoned that insects must have color vision, but was not able to scientifically demonstrate it.
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Polar opposite

This figure illustrates the direction tuning curves of two motion sensitive neurons recorded in the primary visual cortex. The two neurons were so close to each other that their activities could be picked up by the same electrode. Interestingly they preferred polar opposite directions.

The California ground squirrel

I took these photos for a research project while I was a student at UC San Diego. They are the skull and the brain of the California ground squirrel (Spermophilus beecheyi)