Scientists at Queen Mary University of London discovered the bees' memory lapse through series of training exercises. First, researchers trained the bees to associate a black-ringed flower with food. Bees soon only targeted this flower. After a few days, researchers changed things up, training the bees to associate food with a yellow flower. The bees obliged, now ignoring the black-ringed flowers in favor of the yellow ones.
After a few days, the scientists presented the bees with a range of flower designs and found the test subjects preferred yellow flowers accented with black rings. The bees had confused their old memories.