We can hardly imagine an artificial being without some form of vision, which is deeply embedded in us. Much of the human cortex is devoted to visual cognition, far more than to any other sensory mode. Vision is our most effective means of exploring our surroundings, from detailed closeups to distant panoramas, and, through our superb ability to recognize faces and their expressions, it is critical for social interaction. (People who suffer from the neurological condition called prosopagnosia, the inability to recognize faces, lead difficult lives. One sufferer tells of failing to identify his own mother, who never forgave him.) At a more abstract level, vision is an element in creating mental imagery, because the“mind’s eye”uses some of the same mental facili- ties that carry out visual cognition.
We consider hearing to be our second most important sense. Like vision, it provides us with information about our surroundings, al- though to a lesser extent than in many animals. Working hand-in- glove with the power of speech, it is an important part of human communication, and although many animals use sound to communi- cate, language is a preeminent human ability—along with vision, one of our highest mental functions. Just as the act of seeing goes beyond the mere reception of light waves and attaches meaning to the images the waves form, meaningful speaking and listening go beyond the mere production and reception of sound waves.
Touch, taste, and smell require less mental processing than vision and hearing, and they engage the world more directly. With vision and hearing, we receive only energy;nothing material enters the body. Taste and smell, however, are the chemical senses that react to mol- ecules actually penetrating the body. Tactile sensors in the skin also physically contact reality, determining what is hard or soft, hot or cold, enabling the hands to actively grasp and shape objects, and pro- viding the emotional warmth of the human touch.
Emulating vision, hearing and speech, and haptic abilities would go far toward producing an effective artificial creature—possibly one that could develop further through its embodiment,as Rodney Brooks has proposed.This program omits smell and taste, which are essential for many living beings, as in the exquisite sense of smell in dogs, or