Goldfish don't just vacantly open and close their mouths and swim round in circles, they also do musical appreciation, it seems.
In the latest piece of baffling research, reported in the scientific journal, Animal Learning and Behavior, scientists have established that not only do fish think and remember; they can appreciate tunes from Delta blues to Classical.
Scientists played CDs to fish for four years to establish they can identify a few bars of Schubert's Trout Quintet, and Paganini's Variations, as well as recognise the difference between Muddy Waters and Sonny Boy Williamson.
Researchers say the results, based on a study of the carp family, suggest that fish are much brighter than has been thought and their brains may process sounds in a way that is comparable with humans.
"Prior to these experiments, there was scepticism about whether carp could discriminate one piece of music from another. Now it appears they can appreciate tunes, melodic patterns and even classify music by artistic genre," says Ava Chase who carried out the research.
Future work is likely to look at musical preferences among fish, an experiment that may determine whether the glazed look of a domestic goldfish is down to boredom or the owner's musical choices.
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