Contrary to the previously accepted notion that animals solve problems by trial and error, he deduced from his experiments on primates that there is actually a thinking process that goes on when some animals are confronted with a problem. Based on these observations he wrote a book called Mentality of Apes.
Some of his psychological experiments conducted on the islands also involved drawing associations between sounds and objects. The phenomenon now known as the Bouba-Kiki Effect was originally his work. He showed the islanders two shapes, a jagged spiky one and the other with rounded edges, like a blob. As the words ‘spiky’ and ‘blob-like’ have a certain harsh and soft tone to them, respectively, so it was with the words that the locals described the objects with—baluba and takiti. This experiment was repeated in South India amongst Tamil and English speaking natives and the results were similar 95% of the time, suggesting again that the brain is able to deduce more than it is offered—in this case a sound from an object (Ramachandran)