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The Cognitive Abilities of Fish
ulum Broen

Fish are the forgotten majority. They com- ours. Red, for instance, seems to be univer-
prise more than 50% of the total vertebrate sally attractive perhaps because red coloured
diversity but are seldom represented in zoos. prey are rich in keratin which is a limiting
Naturally they are the showcase of public resource. It has been theorised that some spe-
aquariums the world over. While most people cies have incorporated red into their mating
don’t think of fish as being intelligent, there is displays to make the most of this pre‐existing
a huge body of research that suggest that they sensory bias (Seehausen et al. 2008). Classic
match the rest of the vertebrates in just about examples include guppies (Poeciliilia reticu-
every facet (Bshary and Brown 2014; Brown late) and sticklebacks (Gasterosteus aculea-
2015). Indeed, evolutionary theory tells us tus). When given a choice between two
that all vertebrates are simply modified fish, foraging patches, one indicated by a red
thus from this perspective perhaps the find- marker and another by a neutral coloured
ing that fish are smart is less surprising. Fish marker (e.g. green), many species of fish will
cognition has a pronounced influence on show a natural tendency to forage near the
their behaviour, which is of direct relevance red marker (e.g. Laland and Williams 1997).
to housing them in captivity. Studies examining spatial learning in guppies
In order to understand fish behaviour it is where fish are required to swim through a
vital to gain a glimpse into how they view the tunnel to access a foraging site show that a
world around them (their umwelt). Let us pre‐existing bias for red makes it much easier
begin with vision since most people can relate to train them to swim through the red tunnel
to the visual world. The standard fish is tetra- as opposed to some other colour (Laland and
chromatic although many species have more Williams 1997). Fish also have a degree of
visual pigments than this and some, such as unconscious visual processing and thus fall
deep sea fish, have none. Most fish can see for the same sorts of visual illusions as
colours more vividly than we can. For the humans. For example, both sharks and bony
majority of shallow water species this means fish can discriminate between Kanizsa figures
colour is very important to them. Colour is (Fuss et al. 2014).
used during courtship and foraging for To date much of the research on spatial
instance. In cichlid fish, for example, varia- learning in fish has tended to focus on visual
tion in colour and preferences for certain col- cues. Fish are capable of using a single cue (a
ours has led to massive species diversification beacon) to locate a given location. They can
(Seehausen et al. 2008). Many fish have innate also use integration by relying on the relative
colour preferences, which means it is easier to position of a number of beacons to locate a
train them when using these preferred col- specific spot. If you test their spatial learning

Zoo Animal Learning and Training, First Edition. Edited by Vicky A. Melfi, Nicole R. Dorey, and Samantha J. Ward.
© 2020 John Wiley & Sons Ltd. Published 2020 by John Wiley & Sons Ltd.