Virtually all of us recognize the color red as warm and blue as cold. These associations are acquired through cultural exposure, but this has also been demonstrated in infants and apes, suggesting some associations are innate. In the TED-Ed YouTube video “Ideasthesia: How do ideas feel?” Danko Nikolic, associated with the Max-Planck Institute for Brain Research in Germany and pioneer of the concept “ideasthesia” (feeling ideas) illustrates how our sensory perceptions are shaped by our conceptual understanding of the world and how this is a fundamental part of our lives.

“The traditional model of our mental function has been that the senses provide separate data to our brain, which are then translated into the appropriate mental phenomena,” Nikolic says. Examples of this include how our brain processes light into visual images and air vibrations into auditory experiences. However, he ponders how our brain can translate the input of our animal senses into the seemingly non-physical experiences we call thoughts.

Unlike synesthesia, which is when two sensory sections of the brain are crossed, connect, or combined to cause a different kind of enhanced sense, ideathesia shows how associations between unrelated stimuli rely on an intellectual understanding of each stimulus rather than the stimulus itself. In other words, it’s an experience with a somatic sensory connection rather than just the senses.

Nikolic used the example of the Bouba/Kiki Effect, a 2006 study published in the journal Developmental Science. Researchers showed participants, including infants, two shapes and asked them which one was Bouba and which one was Kiki. Most of the participants immediately choose Kiki for the jagged star-like shape and Bouba for the rounded curvy shape. This is a prime example of synesthesia, where sensory inputs involuntarily activate an unrelated sensory experience.

However, the participants also associated a sensory input with a semantic label rather than two independent sensory experiences. The words Kiki and Bouba are associated with a wider range of stimuli. There is even an online game by Heston Blumenthal’s Fat Duck Restaurant in which you are presented with pictures of various food items and asked whether they are “more Kiki or Bouba.” Strong-tasting foods like lemon have been consistently rated as more “Kiki,” whereas items like eggs are seen as more “Bouba.” This is a prime example of high-level ideasthesia, which links multiple sensory and semantic experiences together in an abstract manner.

Ideasthesia demonstrates the ability of the human brain of activating concepts to evoke perception-like experiences. This is why metaphors make sense to us, such as how snow is compared to a white blanket, because they have shared sensations of softness and lightness, combining the conceptual and emotional. Overall, Nikolic says, “The network of associations formed by ideasthesia may not only be similar to our linguistic network, but may in fact be an integral part of it.”