The Secret Life of the Mind: How Our Brain Thinks, Feels and Decides. Mariano Sigman

touched. Does the same thing happen with a blind adult who begins to see? The answer to this question only recently became possible once surgeries were able to reverse the thick cataracts that cause congenital blindness.

      The first actual materialization of Molyneux’s mental experiment was done by the Italian ophthalmologist Alberto Valvo. John Locke’s prophecy was correct; for a congenitally blind person, gaining sight was nothing like the dream they had longed for. This was what one of the patients said after the surgery that allowed him to see:

      I had the feeling that I had started a new life, but there were moments when I felt depressed and disheartened, when I realized how difficult it was to understand the visual world. [ … ] In fact, I see groups of lights and shadows around me [ … ] like a mosaic of shifting sensations whose meaning I don’t understand. [ … ] At night, I like the darkness. I had to die as a blind person in order to be reborn as a seeing person.

      This patient felt so challenged by suddenly gaining sight because while his eyes had been ‘opened’ by the surgery, he still had to learn to see. It was a big and tiresome effort to put together the new visual experience with the conceptual world he had built through his senses of hearing and touch. Meltzoff proved that the human brain has the ability to establish spontaneous correspondences between sensory modalities. And Valvo showed that this ability atrophies when in disuse over the course of a blind life.

      On the contrary, when we experience different sensory modalities, some correspondences between them consolidate spontaneously over time. To prove this, my friend and colleague Edward Hubbard, along with Vaidyanathan Ramachandran, created the two shapes that we see here. One is Kiki and the other is Bouba. The question is: which is which?

      Almost everyone answers that the one on the left is Bouba and the one on the right is Kiki. It seems obvious, as if it couldn’t be any other way. Yet there is something strange in that correspondence; it’s like saying someone looks like a Carlos. The explanation for this is that when we pronounce the vowels /o/y/u/, our lips form a wide circle, which corresponds to the roundness of Bouba. And when saying the /k/, or /i/, the back part of the tongue rises and touches the palate in a very angular configuration. So the pointy shape naturally corresponds with the name Kiki.

      These bridges often have a cultural basis, forged by language. For example, most of the world thinks that the past is behind us and the future is forward. But that is arbitrary. For example, the Aymara, a people from the Andean region of South America, conceive of the association between time and space differently. In Aymara, the word ‘nayra’ means past but also means in front, in view. And the word ‘quipa’, which means future, also indicates behind. Which is to say that in the Aymaran language the past is ahead and the future behind. We know that this reflects their way of thinking, because they also express that relationship with their bodies. The Aymara extend their arms backwards to refer to the future and forwards to allude to the past. While on the face of it this may seem strange, when they explain it, it seems so reasonable that we feel tempted to change our own way of envisioning it; they say that the past is the only thing we know – what our eyes see – and therefore it is in front of us. The future is the unknown – what our eyes do not know – and thus it is at our backs. The Aymara walk backwards through their timeline. Thus, the uncertain, unknown future is behind and gradually comes into view as it becomes the past.

      We designed an atypical experiment, with the linguist Marco Trevisan and the musician Bruno Mesz, in order to find out whether there is a natural correspondence between music and taste. The experiment brought together musicians, chefs and neuroscientists. The musicians were asked to improvise on the piano, based on the four canonical flavours: sweet, salty, sour and bitter. Of course, coming from different musical schools and styles (jazz, rock, classical, etc.) each one of them had their own distinctive interpretation. But within that wide variety we found that each taste inspired consistent patterns: the bitter corresponded with deep, continuous tones; the salty with notes that were far apart (staccato); the sour with very high-pitched, dissonant melodies; and the sweet with consonant, slow and gentle music. In this way we were able to salt ‘Isn’t She Lovely’ by Stevie Wonder and to make a sour version of The White Album by the Beatles.

The mirror between perception and action

      Our representation of time is random and fickle. The phrase ‘Christmas is fast approaching’ is strange. Approaching from where? Does it come from the south, the north, the west? Actually, Christmas isn’t located anywhere. It is in time. This phrase, or the analogous one, ‘we’re getting close to the end of the year’, reveals something of how our minds organize our thoughts. We do it in our bodies. Which is why we talk of the head of government, of someone’s right-hand man, the armpit of the world and many other metaphors^fn1 that reflect how we organize thought in a template defined by our own bodies. And because of that, when we think of others’ actions, we do so by acting them out ourselves, speaking others’ words in our own voice, yawning someone else’s yawn and laughing someone else’s laugh. You can do a simple experiment at home to test out this mechanism. During a conversation, cross your arms. It’s very likely that the person you are speaking to will do the same. You can take it further with bolder gestures, like touching your head, or scratching yourself, or stretching. The probability that the other person will imitate you is high.

      This mechanism depends on a cerebral system made up of mirror neurons. Each one of these neurons codifies specific gestures, like moving an arm or opening up a hand, but it does so whether or not the action is our own or someone else’s. Just as the brain has a mechanism that spontaneously amalgamates information from different sensory modes, the mirror system allows – also spontaneously – our actions and others’ actions to be brought together. Lifting your arm and watching someone else do it are very different processes, since one is done by you and the other is not. As such, one is visual and the other is motor. However, from a conceptual standpoint, they are quite similar. They both correspond to the same gesture in the abstract world.

      And now after understanding how we adults merge sensory modalities in music, in shapes and sounds and in language, and how we bring together perception and action, we go back to the infant mind, specifically to ask whether the mirror system is learned or whether it is innate. Can newborns understand that their own actions correspond to the observation of another person’s? Meltzoff also tested this out, to put an end to the empirical idea that considers the brain a tabula rasa.

      Meltzoff proposed another experiment, in which he made three different types of face at a baby: sticking out his tongue, opening his mouth, and pursing his lips as if he were about to give the child a kiss. He observed that the baby tended to repeat each of his gestures. The imitation wasn’t exact or synchronized; the mirror is not a perfect one. But, on average, it was much more likely that the baby would replicate the gesture he or she observed than make one of the other two. Which is to say that newborns are capable of associating observed actions with their own, although the imitation is not as precise as it will later become when language is introduced.

      Meltzoff’s two discoveries – the associations between our actions and those of others, and between varying sensory modalities – were published in 1977 and 1979. By 1980, the empirical dogma was almost completely dismantled. In order to deal it a final death blow, there was one last mystery to be solved: Piaget’s mistake.^fn2

Piaget’s mistake!

      One of the loveliest experiments done by the renowned Swiss psychologist Jean Piaget is the one called A-not-B. The first part goes like this: there are two napkins on a table, one on each side. A ten-month-old baby is shown an object, then it is covered with the first napkin (called ‘A’). The baby finds it without difficulty or hesitation.

      Behind this seemingly