Humans have a unique capacity to assign to things and events certain meanings that the senses alone cannot comprehend. This consistent ability, called "symboling," has been proposed by many experts to be a more suitable explanation as to how humans differ from other animals. Language is a good example of this ability. In speech, the meaning of the words we utter is not entirely inherent in the sounds themselves. Humans assign meaning to those sounds freely and arbitrarily. This is the essence of symboling.

How did humans come to develop the ability to symbol? Oddly enough, it all began with posture. Erect posture freed the arms and hands of our ancestors from its earlier function of locomotion. This made possible an extensive and versatile use of tools and the eye-hand-object coordination involved in using tools stimulated the growth of the brain, especially the forebrain. This enlargement and specialization of the brain allowed for refined control of the lips and tongue, which allowed for the development of, you guessed it, speech! And speech, as mentioned earlier, is one of best examples of symboling.