Perception is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system, which in turn result from physical or chemical stimulation of the sensory system. Vision involves light striking the retina of the eye; smell is mediated by odor molecules; and hearing involves pressure waves.
An illusion is a distortion of the senses, which can reveal how the mind normally organizes and interprets sensory stimulation. Although illusions distort the human perception of reality, they are generally shared by most people.
Haptic technology is technology that can create an experience of touch by applying forces, vibrations, or motions to the user. These technologies can be used to create virtual objects in a computer simulation, to control virtual objects, and to enhance remote control of machines and devices (telerobotics). Haptic devices may incorporate tactile sensors that measure forces exerted by the user on the interface. The word haptic, from the Greek: ἁπτικός (haptikos), means "tactile, pertaining to the sense of touch". Simple haptic devices are common in the form of game controllers, joysticks, and steering wheels.
Stimulus modality, also called sensory modality, is one aspect of a stimulus or what is perceived after a stimulus. For example, the temperature modality is registered after heat or cold stimulate a receptor. Some sensory modalities include: light, sound, temperature, taste, pressure, and smell. The type and location of the sensory receptor activated by the stimulus plays the primary role in coding the sensation. All sensory modalities work together to heighten stimuli sensation when necessary.
Multisensory integration, also known as multimodal integration, is the study of how information from the different sensory modalities may be integrated by the nervous system. A coherent representation of objects combining modalities enables animals to have meaningful perceptual experiences. Indeed, multisensory integration is central to adaptive behavior because it allows animals to perceive a world of coherent perceptual entities. Multisensory integration also deals with how different sensory modalities interact with one another and alter each other's processing.
Sensory substitution is a change of the characteristics of one sensory modality into stimuli of another sensory modality.
The kappa effect or perceptual time dilation is a temporal perceptual illusion that can arise when observers judge the elapsed time between sensory stimuli applied sequentially at different locations. In perceiving a sequence of consecutive stimuli, subjects tend to overestimate the elapsed time between two successive stimuli when the distance between the stimuli is sufficiently large, and to underestimate the elapsed time when the distance is sufficiently small.
The tau effect is a spatial perceptual illusion that arises when observers judge the distance between consecutive stimuli in a stimulus sequence. When the distance from one stimulus to the next is constant, and the time elapsed from one stimulus to the next is also constant, subjects tend to judge the distances, correctly, as equal. However, if the distance from one stimulus to the next is constant, but the time elapsed from one stimulus to the next is not constant, then subjects tend to misperceive the interval that has the shorter temporal interval as also having a shorter spatial interval. Thus, the tau effect reveals that stimulus timing affects the perception of stimulus spacing. Time is also a perceived quantity and subject to its own illusions; research indicates that in the tau effect, perceived stimulus spacing follows perceived (phenomenal) time rather than actual (physical) time.
In perceptual psychology, a sensory cue is a statistic or signal that can be extracted from the sensory input by a perceiver, that indicates the state of some property of the world that the perceiver is interested in perceiving.
The study of time perception or chronoception is a field within psychology, cognitive linguistics and neuroscience that refers to the subjective experience, or sense, of time, which is measured by someone's own perception of the duration of the indefinite and unfolding of events. The perceived time interval between two successive events is referred to as perceived duration. Though directly experiencing or understanding another person's perception of time is not possible, perception can be objectively studied and inferred through a number of scientific experiments. Some temporal illusions help to expose the underlying neural mechanisms of time perception.
The cutaneous rabbit illusion is a tactile illusion evoked by tapping two or more separate regions of the skin in rapid succession. The illusion is most readily evoked on regions of the body surface that have relatively poor spatial acuity, such as the forearm. A rapid sequence of taps delivered first near the wrist and then near the elbow creates the sensation of sequential taps hopping up the arm from the wrist towards the elbow, although no physical stimulus was applied between the two actual stimulus locations. Similarly, stimuli delivered first near the elbow then near the wrist evoke the illusory perception of taps hopping from elbow towards wrist. The illusion was discovered by Frank Geldard and Carl Sherrick of Princeton University, in the early 1970s, and further characterized by Geldard (1982) and in many subsequent studies. Geldard and Sherrick likened the perception to that of a rabbit hopping along the skin, giving the phenomenon its name. While the rabbit illusion has been most extensively studied in the tactile domain, analogous sensory saltation illusions have been observed in audition and vision. The word "saltation" refers to the leaping or jumping nature of the percept.
Two-point discrimination (2PD) is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one. It is often tested with two sharp points during a neurological examination and is assumed to reflect how finely innervated an area of skin is.
Haptic perception means literally the ability "to grasp something". Perception in this case is achieved through the active exploration of surfaces and objects by a moving subject, as opposed to passive contact by a static subject during tactile perception.
Touch is perceiving the environment using skin. Specialized receptors in the skin send signals to the brain indicating light and soft pressure, hot and cold, body position and pain. It is a subset of the sensory nervous system, which also includes the visual, auditory, olfactory, gustatory and vestibular senses.
Perceptual learning is learning better perception skills such as differentiating two musical tones from one another or categorizations of spatial and temporal patterns relevant to real-world expertise. Examples of this may include reading, seeing relations among chess pieces, and knowing whether or not an X-ray image shows a tumor.
Amorphosynthesis, also called a hemi-sensory deficit, is a neuropsychological condition in which a patient experiences unilateral inattention to sensory input. This phenomenon is frequently associated with damage to the right cerebral hemisphere resulting in severe sensory deficits that are observed on the contralesional (left) side of the body. A right-sided deficit is less commonly observed and the effects are reported to be temporary and minor. Evidence suggests that the right cerebral hemisphere has a dominant role in attention and awareness to somatic sensations through ipsilateral and contralateral stimulation. In contrast, the left cerebral hemisphere is activated only by contralateral stimuli. Thus, the left and right cerebral hemispheres exhibit redundant processing to the right-side of the body and a lesion to the left cerebral hemisphere can be compensated by the ipsiversive processes of the right cerebral hemisphere. For this reason, right-sided amorphosynthesis is less often observed and is generally associated with bilateral lesions.
In psychology, visual capture is the dominance of vision over other sense modalities in creating a percept. In this process, the visual senses influence the other parts of the somatosensory system, to result in a perceived environment that is not congruent with the actual stimuli. Through this phenomenon, the visual system is able to disregard what other information a different sensory system is conveying, and provide a logical explanation for whatever output the environment provides. Visual capture allows one to interpret the location of sound as well as the sensation of touch without actually relying on those stimuli but rather creating an output that allows the individual to perceive a coherent environment.
Haptic memory is the form of sensory memory specific to touch stimuli. Haptic memory is used regularly when assessing the necessary forces for gripping and interacting with familiar objects. It may also influence one's interactions with novel objects of an apparently similar size and density. Similar to visual iconic memory, traces of haptically acquired information are short lived and prone to decay after approximately two seconds. Haptic memory is best for stimuli applied to areas of the skin that are more sensitive to touch. Haptics involves at least two subsystems; cutaneous, or everything skin related, and kinesthetic, or joint angle and the relative location of body. Haptics generally involves active, manual examination and is quite capable of processing physical traits of objects and surfaces.
Visuo-haptic mixed reality (VHMR) is a branch of mixed reality that has the ability of merging visual and tactile perceptions of both virtual and real objects with a collocated approach. The first known system to overlay augmented haptic perceptions on direct views of the real world is the Virtual Fixtures system developed in 1992 at the US Air Force Research Laboratories. Like any emerging technology, the development of the VHMR systems is accompanied by challenges that, in this case, deal with the efforts to enhance the multi-modal human perception with the user-computer interface and interaction devices at the moment available. Visuo-haptic mixed reality (VHMR) consists of adding to a real scene the ability to see and touch virtual objects. It requires the use of see-through display technology for visually mixing real and virtual objects and haptic devices necessary to provide haptic stimuli to the user while interacting with the virtual objects. A VHMR setup allows the user to perceive visual and kinesthetic stimuli in a co-located manner, i.e., the user can see and touch virtual objects at the same spatial location. This setup overcomes the limits of the traditional one, i.e, display and haptic device, because the visuo-haptic co-location of the user's hand and a virtual tool improve the sensory integration of multimodal cues and makes the interaction more natural. But it also comes with technological challenges in order to improve the naturalness of the perceptual experience.
Vincent Hayward, was a scientist and engineer. His reaserch focus was on touch and haptics. He was a professor at Sorbonne University, Institute of Intelligent Systems and Robotics (ISIR), where since 2008 he led a team dedicated to the study of tactile perception and the development of haptic devices. In 2020, he was elected to the French Academy of sciences.
