Somewhat related : Pretty much everything that has a nervous system has the potential to display some degree of intelligence, depending on how the nervous system is structured.
Even in 2017, most people are still very misguided when it comes to neuroscience, thinking that the volume of the central nervous system is directly related to cognitive processes, although research shows that the extent of cognitive functions is unrelated to CNS volume, and instead related to the architecture of the synaptic connections.
For example, as far as we know, bees, bumblebees and other social arthropods are a lot more intelligent than many other animals that have similarly-sized nervous systems. Bees and bumblebees are able to learn to solve problems that are unrelated to situations that they would normally encounter, and being able to actively teach solutions to other bees.