Fish can count

Fish can count up to five, well some fish can. This was research carried out by the University of Bonn. Eight stingrays and eight zebra mbuna were presented with cards featuring blue shapes which meant they had to add one, or cards with yellow shapes which meant they had to subtract one. The fish then faced two gates, one of which showed a card with the initial number of shapes plus one while the other gate showed a card with one shape removed. They were given a food reward if they swam through the correct gate. Six of the zebra mbuna and three of the stingrays consistently associated blue with addition and yellow with subtraction. 

Jane