Most animals that live in groups have the capability to produce at least a few specific auditory, visual (e.g. gestures and displays), chemical (e.g. pheromones) or other signals in response to particular situations such as danger. Some animals have also been found to produce much more complex and varied signals. For example it was discovered in the 1980s that elephants can generate elaborate patterns of sounds—but at frequencies below human hearing. Animals such as octopuses and particularly cuttlefish can show complex and changing patterns of pigmentation. But despite a fair amount of investigation it remains unclear whether these represent more than just simple responses to the environment.