A new study using high definition television (HDTV) has revealed that the Octopus may be the Jekyll and Hyde of the ocean, as it is aggressive one day, while shrinking violets the next, which suggests that the animal doesn't have a personality.

According to a report in New Scientist, the study, by Renata Pronk at Macquarie University in Sydney, Australia, and colleagues, found that gloomy octopuses reacted to films shown on liquid crystal HDTV as if they were seeing the real thing.

"They lunge forwards to attack crabs and back off from other octopuses, much as they do in the wild," said Roger Hanlon, an octopus researcher at the Marine Resources Center, Woods Hole, Massachusetts.

Surprisingly, an octopus that was bold, aggressive and exploratory on one day was just as likely to be shy, submissive and stationary the next.

"This suggests that the gloomy octopus does not have personality," said Pronk.

By "personality", researchers mean consistency in behaviour.

You might expect an individual to respond to crabs, other octopuses, jars, for example, by being consistently bold, shy or aggressive.

In contrast, the octopuses in Pronk's study were more moody than gloomy.

The team captured 31 gloomy octopuses in Sydney harbour and showed them a set of 3-minute videos displayed on a screen at the front of their tank.

The videos were filmed at 50 frames per second and featured a crab (their prey), another gloomy octopus, a jar and a water-filled aquarium.

To Pronk's surprise, the octopuses behaved as if animals in the film were real. They lunged forwards at crabs using jet propulsion, often striking the front of the aquarium.

But when they saw films of other octopuses, which they avoid in the wild, they cowered behind a terracotta pot placed in the aquarium.

Octopuses that reacted to one film aggressively tended to respond to all films on a particularly day in the same way.

But over longer periods of time, any trace of "personality" or consistency evaporated.

They might react aggressively one day, but much less so on another day.

This lack of consistent behaviour may be related to octopuses's huge brain size, relative to other cephalopods.

Big brains may "afford octopuses considerable behavioural flexibility that allows them to change their behaviour adaptively over time," according to the researchers. (ANI)