Sunday, 28 August 2016

Cuttlefish found to have number sense and state-dependent valuation

August 24, 2016 by Bob Yirka

 (—A pair of researchers with National Tsing Hua University in Taiwan has found that cuttlefish have both number sense and state-dependent valuation. In their paper published in Proceedings of the Royal Society B, Tsang-I Yang and Chuan-Chin Chiao describe a series of experiments they carried out with cuttlefish and what they learned about the cephalopods.

Human beings very clearly have number sense—from a very early age, they are able to make judgments about objects in the world around them based on how many of them there are. But few other animals have this ability. In this new effort, the research pair wondered if cuttlefish might because prior studies have shown them to have one of the more complex invertebrate brains. To find out, they set up a series of experiments all based around a type of food: shrimp.

The experiments consisted of offering young cuttlefish choices for a meal—a dead shrimp or a live one, a large shrimp or a small one, or two different quantities of shrimp—and then noting how the cuttlefish responded.

The researchers found that the cuttlefish, quite naturally, preferred the live shrimp over the dead ones, but their decision making was more nuanced than that. They preferred a large shrimp over two smaller ones when they were hungry, for example, but chose the small ones when they were not. Perhaps most interesting were the results found when the cuttlefish were given quantity options, e.g., one versus two shrimp, two versus three, three versus four and four versus five—they almost always chose the larger quantity option.

The researchers suggest these findings indicate that cuttlefish have number sense (they could see and comprehend that there were more or fewer shrimp in different groups) and that their choice of prey could depend on how hungry they were or the quality of the available prey—a form of state-dependent valuation. Such behavior also suggests that cuttlefish are capable of using both external (environmental conditions) and internal (their own preferences) information when making prey choices. Indeed, the researchers report that it appeared the cuttlefish at times took a moment to think over their choices before deciding which they preferred.

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