- So they designed another test, for six common cuttlefish. The cuttlefish were placed in a special tank with two enclosed chambers that had transparent doors so the animals could see inside. In the chambers were snacks - a less-preferred piece of raw king prawn in one, and a much more enticing live grass shrimp in the other.
The doors also had symbols on them that the cuttlefish had been trained to recognise. A circle meant the door would open straight away. A triangle meant the door would open after a time interval between 10 and 130 seconds. And a square, used only in the control condition, meant the door stayed closed indefinitely.