- Editor: Prof. Tony J. Prescott, Dept Psychology, Univ of Sheffield, UK
- Editor: Prof. Ehud Ahissar, Dept of Neurobiology, The Weizmann Inst, Rehovot
Touch is the ability to understand the world through physical contact. The noun “touch” and the verb “to touch” derive from the Old French verb “tochier”. Touch perception is also described by the adjectives tactile, from the Latin “tactilis”, and haptic, from the Greek “haptόs”. Academic research concerned with touch is also often described as haptics.
The aim of the Scholarpedia Encyclopedia of Touch is to provide a comprehensive set of articles, written by leading researchers and peer-reviewed by fellow scientists, detailing the current scientific understanding of the sense of touch and of its neural substrates in animals including humans. It is hoped that the encyclopedia will encourage sharing of ideas and insights between researchers working on different aspects of touch and in different species, including research in synthetic touch systems. In addition it is hoped that the encyclopedia will raise awareness of research in tactile sensing and promote increased scientific and public interest in the field.
Our encyclopedia assembles a state-of-the-art understanding of the sense of touch across a broad range of species from invertebrates such as stick insects and spiders, terrestrial and marine mammals, through to humans. The different contributions show not only the varieties of touch—antennae, whiskers, fingertips—but also their commonalities. They explore how touch sensing has evolved in different animal lineages, how it serves to provide rapid and reliable cues for controlling ongoing behaviour, how it develops, and how it can disintegrate when our brains begin to fail. In addition to analysing natural touch, we also consider how engineering is beginning to exploit physical analogues of these biological systems so as to endow robots, and other engineered artefacts, with rich tactile sensing capabilities.
Scope and Structure
Following an introductory chapter—The World of Touch—our encyclopedia is structured into four sections:
- Comparative touch: There are a large number of specialist tactile sensory organs in the animal kingdom. This section contains articles on animal species that exhibit interesting or exceptional tactile sensing abilities. We particularly focus of antennal systems in insects, and on vibrissal systems in both terrestrial and marine mammals.
- The psychology of touch: The study of human cutaneous touch has a rich and long history in psychology and psychophysics. The pioneering studies of Ernst Weber (1795-1878) distinguished different forms of touch—pressure, temperature and pain—all of which are separately considered in our encyclopedia along with dynamical (effortful) touch and the tactile perception of force, along with some relevant forms of interoception (internal sensing) and proprioception (sense of body position). A particular focus of recent research has been towards the combination of tactile sensing with manipulation and grasp in the human hand. Alongside the study of healthy touch, this section also considers research on touch disorders, the loss of tactile acuity with ageing, and the phenomenon of phantom touch.
- The neuroscience of touch: A scientific understanding of the biological substrates for tactile sensing is beginning to emerge at all levels from the sensory periphery through to the somatosensory and multimodal areas of cortex. Perhaps more than other sensory modality, tactile sensing is critically dependent on the movement of the sensing apparatus, therefore touch is increasingly studies from an active perception perspective—understanding active touch (in contrast to passive touch) as an intentional, information-seeking activity that combines sensing with actuation. The investigation of the sensorimotor control loops involved in mammalian active touch has been significantly advanced by the availability of the rodent vibrissal sensory system as an animal model. This section therefore combines studies in both primates (including humans) and rodents to show how neurobiological research is beginning to demonstrate an in-depth understanding of tactile sensing systems in mammals.
- Synthetic Touch: Touch sensing is giving rise to a range of exciting new technologies. This section highlights some of the most promising from tactile sensors for robots and haptic displays for the visually-impaired, through to virtual touch systems that can allow the extension of touch, through telecommunication technologies, as a modality for communication.
The Encyclopedia went online in February 2008 and was substantially revised and extended December 2014 to March 2015. Contributors to the Encyclopedia include:
Wouter Bergmann Tiest,
Moritz von Heimendahl,
Haike van Stralen,
Jean Louis Thonnard,
The Encyclopedia of Touch was part-sponsored by the European Union Framework 7 project BIOTACT (BIOmimetic Technology for vibrissal ACtive Touch) (FP7-ICT-215910), one of whose goals was to promote research in the fields of natural and synthetic tactile sensing. Tony Prescott's contribution to editing the Encyclopaedia was also assisted by support from the Framework 7 Co-ordination Action "The Convergent Science Network of Biomimetics and Neurotechnology" (FP7-ICT-601167). The collaboration between the editors was facilitated by support from a Weizmann-UK grant from the Weizmann Institute of Science.
The following Scholarpedia Assistants provided substantial assistance to the specified articles:
Swetamber Das (Tactile temporal order, Imaging human touch, Whisking control by motor cortex), Javier Elkin (Touch in aging), Serguei A. Mokhov (Models of tactile perception and development, Systems Neuroscience of Touch), Shruti Muralidhar (S1 microcircuits, Tactile object perception), Abdellatif Nemri (Dynamic touch), B. Lungsi Sharma (A spider's tactile hairs), and Juzar Thingna (Tactile Substitution for Vision, Whisking pattern generation).
Additionally, Nick Orbeck provided copy-editing for most of the articles.