Artificial selection for large and small relative brain size in guppies (Poecilia reticulata) results in differences in cognitive ability

• Main Author: Bundsen, Andreas
• Format: Bachelor Thesis
• Language: English
• Published: Uppsala universitet, Institutionen för biologisk grundutbildning 2012
• Subjects: cognition; guppy; artificial selection; brain size; Physeter macrocephalus
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-192953

Vertebrate brain size is remarkably variable at all taxonomic levels. Brains of mammals forexample, range from 0.1 gram in small bats (Chiroptera) to about 8-9 kilos in Sperm whales(Physeter macrocephalus). But what does this variation in size really mean? The link between brainsize and cognition is debated due to, for instance the difficulties of comparing cognitive ability indifferent species. A large number of comparative studies continue to provide information aboutcorrelations found both within and between species. The relative size of the brain is an example of apopular measurement that correlates with cognitive ability. But to date, no experimental studieshave yielded any proof causality between relative brain size and cognitive ability. Here I usedguppies selected for either large or small relative brain size to investigate differences in cognitiveperformance of a quantity discrimination task. The results from this experiment provideexperimental evidence that relative brain size is important for cognitive ability, and that a differencein cognitive ability could be obtained already after two generations of selection experiments onrelative brain size in a vertebrate. Artificial Selection on Relative Brain Size in the Guppy Reveals Costs and benefits of Evolving a Larger Brain