Exactly what you think or chose to believe about dolphin intelligence will depend entirely on what your definition of intelligence is. If intelligence is existing in a life which is about more than just basic survival, then there are many arguments which can be made in favor of dolphins being a highly intelligent species.
They eat incredibly efficiently in order to build hours of playtime into their days and they are one of the few animals on the planet, other than humans, to have sex for pleasure rather than just because of a basic animal instinct. They seem to have a sophisticated system of communication which includes individual names for each dolphin in a pod. All of these indicators suggest a significant level of dolphin intelligence.
However, the fact that we cannot understand dolphin communication entirely means that it is very difficult for us as humans to gauge the level of dolphin intelligence. They may be having extremely sophisticated conversations with one another, which would demonstrate a very high level of intelligence, or they may just be telling each other where the nearest food source is. If the latter is true, it proves more about basic animal instinct than it does about the intelligence of the dolphin.
It is also important to note the difference between wild dolphins and dolphins in captivity. It is difficult to carry out investigations and research into the intelligence of dolphins in the wild as tests are required to demonstrate the dolphins’ ability in a number of different tasks. There is no guarantee that dolphins which are captured and kept in captivity will respond in the same way as those living in the wild would do in certain situations. Their environment and stress levels may have a huge impact on the way in which they behave. This makes measuring dolphin intelligence scientifically an immensely difficult undertaking.
One way of studying dolphin intelligence is by looking at their brains. Scientists don’t need to worry about the difference it might make to capture a dolphin if it has already passed away. Of course, researchers can no longer put these brains to the test but they can biologically study the form of dolphins’ brains which can give them some idea of how they operate. For example, dolphins have one of the largest brains in the animal kingdom relative to their size. The dolphin brain is bigger than the human brain which suggests that there is a huge capacity for complex neurological pathways to be formed.