A robot which has the capacity to decide it will inflict pain on humans has been invented - breaking one of the standard rules for artificial intelligence.

From Will Smith movie I, Robot, one of the laws of robotics is commonly considered to be that it cannot injure humans.

But scientists and artist Alexander Reben has invented "The First Law", a robot named for the very rule it breaks.

The basic robot is programmed to be capable of pricking a human's finger.

However, as Mr Reben is intending to provoke discussion on AI, The First Law will not 'decide' to inflict pain every time.

"The robot makes a decision that I as a creator cannot predict - it's causing pain that's not for a useful purpose - we are moving into an ethics question, robots that are specifically built to do things that are ethically dubious."