It is commonly known that dolphins are very intelligent animals. They have been shown to recognise themselves in a mirror meaning that they are a species that can display physical self-awareness. Recent studies also suggest that they are even able to produce personalised whistles that act as ‘names’ for individual members within their pod. It is clear that dolphins possess high levels of cognition and thus intelligence, but how does their intelligence compare to ours?
The encephalization quotient (EQ) is defined as the ratio between actual brain mass and predicted brain mass for an animal of a given size. The EQ is a way of expressing how large or small the brain is of a species compared to other species of the same average body weight. The average EQ is 1.0 whilst the EQ value for humans is 7.0. This means that human brains are 7 times the size that would be expected for a species of the same average body weight.
Whilst humans have the highest EQ, dolphins come in second.
Bottlenose dolphins have bigger brains than humans weighing 1600 grams and 1300 grams respectively. Similarly to humans, dolphins have a complex neocortex, which is the part of the brain that is responsible for problem solving and self-awareness. Dolphin brains have also been found to contain neurons called Von Economo neurons, which have been linked to social cognition and emotions in humans and apes (Sciencemag.org). One very interesting discovery regarding the dolphin brain is that part of their limbic system (the part of the brain that processes emotions in mammals) is actually more elaborate than in the human brain. This adjacent area is known as the paralimbic region (Marino, 2013).
One theory regarding why cetaceans evolved such large brains suggests that their large brains were needed as a response to social forces. Evolving complex social societies requiring communication, collaboration and cooperation may have coincided with an increase in brain size as a result (Marino et al, 2007).
As research continues, we can conclude that the dolphin brain is perhaps even more complex than we thought and could suggest that their social bonds may also be interlinked to other factors such as their ability to process emotions.
Written by Gemma Green, Research Intern 2017
Marino et al., (2007) Cetaceans have complex brains for complex cognition, PLoS Biology, 5 (5).
Inside the mind of a killer whale: A Q+A with the neuroscientist from ‘Blackfish’, Theraptorlab.wordpress.com