NEW YORK • Zipping through water like shimmering arrowheads, cuttlefish are swift, sure hunters - death on eight limbs and two waving tentacles for small creatures in their vicinity.

They morph to match the landscape, shifting between a variety of hues and even textures, using tiny structures that expand and contract beneath their skin.

They even seem to have depth perception, researchers using tiny 3D vision glasses found, placing them apart from octopuses and squids. And their accuracy at striking prey is remarkable.

But for cuttlefish, these physical feats in pursuit of food are not the whole story.

A new study published last month in the Royal Society Open Science journal shows that there is even more to cuttlefish cognition than scientists may have known. They appear to be capable of performing calculations that are more complicated than simply "more food is better".

Presented with a choice between one shrimp or two, they will actually choose the single shrimp after learning from experience that they will be rewarded for this choice.

While the braininess of their octopus cousins gets a lot of attention, researchers who study animal cognition have uncovered surprising talents in cuttlefish over the years.

For instance, the cephalopods will hunt fewer crabs during the day if they learn that shrimp, their preferred food, is predictably available during the night. That shows that they can think ahead.

Biologist Chiao Chuan-chin from Taiwan's National Tsing Hua University, and an author of the study alongside colleague Kuo Tzu-hsin, has found in the past that hungry cuttlefish will pick a bigger, harder-to-catch shrimp to attack.

Those that are not hungry will pick smaller, easier-to-catch ones.

But researchers have also found that animals do not always make decisions that seem logical at first glance.

They found that animals, like humans, respond to their environments using learnt experiences.

In these new experiments, curious to see whether they could alter the value that cuttlefish attach to a single shrimp, the researchers gave the cuttlefish the option of entering a chamber with one shrimp or a chamber with none.

Each time they entered the chamber with a shrimp, the researchers gave them a smaller shrimp as a reward.

Then each cuttlefish took a second test. They could enter a chamber and chase after two shrimps. Or they could enter another chamber that had only one.

"You'd think they always choose the larger quantity," Dr Chiao said. But that was not what happened.

In the second round, the cuttlefish chose one shrimp significantly more often than two.

Cuttlefish that had not undergone the training reliably picked two shrimps over one, demonstrating that cuttlefish that chose the smaller number were anticipating the reward and operating differently than their fellows.

Even waiting until an hour had passed since the initial training did not completely erase the new behaviour.

The process of being rewarded for choosing one shrimp seems to have given that option an extra glow as far as cuttlefish are concerned, Dr Chiao said.

It suggests that they are not simply making basic responses to prey they come across - they are remembering what has come before and using it to make a choice.

Even if in this situation, the behaviour did not result in a bigger haul, it adds to the evidence that cuttlefish are complex creatures, capable of using their brains in ways that may surprise many, the researchers said.

NYTIMES