Desde hace varias décadas los científicos se han preguntado por qué alrededor del 80% de las mujeres, independientemente de si son diestras o zurdas, utilizan el brazo izquierdo para acunar a sus retoños, en lo que parece ser un comportamiento instintivo. El primero en sugerir una explicación fue el psicólogo estadounidense Lee Salk. Inspirándose en el comportamiento de los monos macacos Rhesus, originarios de Asia, propuso quelos latidos del corazón materno eran la causa de tales preferencias. Aunque su teoría estuvo extendida durante un tiempo, estudios posteriores demostraron que, tanto para el feto como para el recién nacido, el sonido predilecto era la voz de su madre, y que los sonidos cardíacos no parecían tener mayor trascendencia.
La hipótesis más fiable llegaba hace unos años de manos de Victoria Bourne y Brenda Todd, de la Universidad británica de Sussex. Estas investigadoras atribuyen la costumbre a un sofisticado proceso en el que están implicados los hemisferios cerebrales de madre e hijo. Así, cuando un niño es acunado en el lado izquierdo de la madre, sus reacciones –llanto, risa, bostezo…– llegan directamente al hemisferio cerebral derecho materno, que es donde se reconocen los gestos emocionales y las expresiones faciales. En consecuencia, se refuerza la relación porque la madre tiene un acceso más rápido e intuitivo a las necesidades del niño.
Fuente: muyinteresante.es

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