Sensation is the physical process during which sensory systems respond to stimuli and provide data for perception. A sense is any of the systems involved in sensation. During sensation, sense organs engage in stimulus collection and transduction. Sensation is often differentiated from the related and dependent concept of perception, which processes and integrates sensory information in order to give meaning to and understand detected stimuli, giving rise to subjective perceptual experience, or qualia. Sensation and perception are central to and precede almost all aspects of cognition, behavior and thought.In organisms, a sensory organ consists of a group of related sensory cells that respond to a specific type of physical stimulus. Via cranial and spinal nerves, the different types of sensory receptor cells (mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors) in sensory organs transduct sensory information from sensory organs towards the central nervous system, to the sensory cortices in the brain, where sensory signals are further processed and interpreted (perceived). Sensory systems, or senses, are often divided into external (exteroception) and internal (interoception) sensory systems. Sensory modalities or submodalities refer to the way sensory information is encoded or transduced. Multimodality integrates different senses into one unified perceptual experience. For example, information from one sense has the potential to influence how information from another is perceived. Sensation and perception are studied by a variety of related fields, most notably psychophysics, neurobiology, cognitive psychology, and cognitive science.Humans have a multitude of sensory systems. Human external sensation is based on the sensory organs of the eyes, ears, skin, nose, and mouth. The corresponding sensory systems of the visual system (sense of vision), auditory system (sense of hearing), somatosensory system (sense of touch), olfactory system (sense of smell), and gustatory system (sense of taste) contribute, respectively, to the perceptions of vision, hearing, touch, smell, and taste (flavor). Internal sensation, or interoception, detects stimuli from internal organs and tissues. Many internal sensory and perceptual systems exist in humans, including the vestibular system (sense of balance) sensed by the inner ear and providing the perception of spatial orientation, proprioception (body position) and nociception (pain). Further internal chemoreception and osmoreception based sensory systems lead to various perceptions, such as hunger, thirst, suffocation, and nausea, or different involuntary behaviors, such as vomiting.Nonhuman animals experience sensation and perception, with varying levels of similarity to and difference from humans and other animal species. For example, mammals, in general, have a stronger sense of smell than humans. Some animal species lack one or more human sensory system analogues, some have sensory systems that are not found in humans, while others process and interpret the same sensory information in very different ways. For example, some animals are able to detect electrical and magnetic fields, air moisture, or polarized light, while others sense and perceive through alternative systems, such as echolocation. Recently, it has been suggested that plants and artificial agents may be able to detect and interpret environmental information in an analogous manner to animals.