body.) Other senses Other senses enable perception of body balance, acceleration, gravity, position of body parts, temperature, and pain. They can also enable perception of internal senses, such as suffocation, gag reflex, abdominal distension, fullness of rectum and urinary bladder, and sensations felt in the throat and lungs. Reality In the case of visual perception, some people can see the percept shift in their mind's eye. Others, who are not picture thinkers, may not necessarily perceive the 'shape-shifting' as their world changes. This esemplastic nature has been demonstrated by an experiment that showed that ambiguous images have multiple interpretations on the perceptual level. The confusing ambiguity of perception is exploited in human technologies such as camouflage and biological mimicry. For example, the wings of European peacock butterflies bear eyespots that birds respond to as though they were the eyes of a dangerous predator. There is also evidence that the brain in some ways operates on a slight "delay" in order to allow nerve impulses from distant parts of the body to be integrated into simultaneous signals. Perception is one of the oldest fields in psychology. The oldest quantitative laws in psychology are Weber's law, which states that the smallest noticeable difference in stimulus intensity is proportional to the intensity of the reference; and Fechner's law, which quantifies the relationship between the intensity of the physical stimulus and its perceptual counterpart (e.g., testing how much darker a computer screen can get before the viewer actually notices). The study of perception gave rise to the Gestalt School of Psychology, with an emphasis on holistic approach. Physiology A sensory system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory receptors, neural pathways, and parts of the brain involved in sensory perception. Commonly recognized sensory systems are those for vision, hearing, somatic sensation (touch), taste and olfaction (smell), as listed above. It has been suggested that the immune system is an overlooked sensory modality. In short, senses are transducers from the physical world to the realm of the mind. The receptive field is the specific part of the world to which a receptor organ and receptor cells respond. For instance, the part of the world an eye can see, is its receptive field; the light that each rod or cone can see, is its receptive field. Receptive fields have been identified for the visual system,