Monday, December 22, 2008

Octopuses and Personality

This article from the Sydney Morning Herald talks about recent work with octopuses done by Macquarie University marine biology researcher Renata Pronk. The article describes two interesting things about the research.

One, it seems that experiments in which they displayed video to the octopuses were more successful with high-definition, 50 frames per second video than with the slower, lower-resolution 25 frames per second.

The second claim is just weird. She says they "have no personality."
"Octopuses," Miss Pronk said, "are very smart. I have seen my octopuses open Vegemite jars by unscrewing the lid. They can find their way through mazes to reach food rewards at the end.

"And they can learn simple puzzles", recognising that symbols, such as squares or circles, mean food is available.

"The definition of personality," she said, "is having repetition in your responses, for example, being consistently bold, or consistently shy, or consistently aggressive."

To resolve the debate she collected 32 common Sydney, or gloomy, octopuses from Chowder Bay, near Mosman, and showed them a series of three-minute videos screened on a monitor in front of their tank.

One video featured a crab, an octopus delicacy.

A second starred another octopus, while a third had a "novel object" they would not have seen: a plastic bottle swinging on a string.

Miss Pronk then watched each octopus for any consistent response pattern, such as boldness or aggression.

When the crab movie was screened "they jetted straight over to the monitor and tried to attack it", she said, adding that was strong evidence they knew they were watching food.

When the octopus movie was screened some became aggressive while others changed their skin camouflage or "would go and hide in a corner, moving as far away as possible".

On viewing the swinging bottle, some puffed themselves up, just in case the object was a threat, while others paid no attention.

But significantly, when the experiment was repeated over several days, she found no consistent response from any octopus. Such random responses implied octopuses have no individual personalities.
So what we're supposed to believe is that the findings support behavioral variation within an individual, but not between individuals?

I'm sorry, but this just doesn't seem to make much sense. I'll grant her definition of personality for a moment. An organism in a population that has a personality would exhibit different patterns of behavior than some other members of the population. In other words, there would be individual differences in behavior among members of the population.

That's exactly what evolutionary theory would predict. In any population, while considering any trait, there will be some type of individual differences. The distribution of variation may be restricted or it may be broad, but it should be there. Variation is the engine which drives natural selection. In a population of bears, for example, some will have thicker fur than others, due to their genes, but also due to their specific developmental path (e.g., their specific diet, etc.). If a change in the regional temperature favors a particular subset of the population (e.g., it gets colder), those individuals better suited to the change will have an advantage, and will be more likely to survive and propagate their genes.

A population with no variation in a trait is evolutionarily stagnant with respect to that trait. I'm no evolutionary biologist, but I'm not even sure it's possible to have a population with absolutely no variation in a given trait. That would have to mean that the genes that encode for and mediate the trait are functionally identical and that any environmental influence on the trait has been exactly the same for all individuals. And with a trait as complex as behavior, I'm just not buying it.

I think Miss Pronk just needs to spend more time with her octopuses.

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