Tactual perception: a review of experimental variables and procedures <s>  <s> Subjects attempted to recognize simple line drawings of common objects using either touch or vision. In the touch condition, subjects explored raised line drawings using the distal pad of the index finger or the distal pads both of the index and of the middle fingers. In the visual condition, a computer-driven display was used to simulate tactual exploration. By moving an electronic pen over a digitizing tablet, the subject could explore a line drawing stored in memory; on the display screen a portion of the drawing appeared to move behind a stationary aperture, in concert with the movement of the pen. This aperture was varied in width, thus simulating the use of one or two fingers. In terms of average recognition accuracy and average response latency, recognition performance was virtually the same in the one-finger touch condition and the simulated one-finger vision condition. Visual recognition performance improved considerably when the visual field size was doubled (simulating two fingers), but tactual... <s> BIB001 </s> Tactual perception: a review of experimental variables and procedures <s>  <s> This tutorial focuses on the sense of touch within the context of a fully active human observer. It is intended for graduate students and researchers outside the discipline who seek an introduction to the rapidly evolving field of human haptics. The tutorial begins with a review of peripheral sensory receptors in skin, muscles, tendons, and joints. We then describe an extensive body of research on “what” and “where” channels, the former dealing with haptic perception of objects, surfaces, and their properties, and the latter with perception of spatial layout on the skin and in external space relative to the perceiver. We conclude with a brief discussion of other significant issues in the field, including vision-touch interactions, affective touch, neural plasticity, and applications. <s> BIB002
Touch is relevant in everyday tasks, and haptic memory allows us to remember the feeling of objects and the touch of other people and is crucial in our everyday life. From picking a coin from our wallet to evaluating the force we need to apply to open a door, we rely on touch in various everyday tasks. Touch has been a relatively unattended sensory modality in cognitive research. Some studies have developed research on touch, but most of the touch literature is driven by perception research, attempting to compare touch with other sensory modalities. When we think about touch, we have to comprehend it as a complex system with more than one sense: touch involves pain perception, temperature perception, proprioception, kinaesthetic perception and tactile perception. In the touchrelated literature, the concepts tactile, haptic and tactual are common and are often presented as synonymous, although they have been defined as distinct concepts previously (e.g., BIB001 . In the present work, we will use them as distinct concepts. Tactile perception refers to the extraction of material properties from the stimuli, such as texture, that are distinct from geometrical properties, such as shape, that usually require a more active interaction with the objects BIB002 ). Tactile perception results from cutaneous variations only BIB001 and is associated with situations of passive touch, in which the participants cannot explore the objects, keeping their hands or fingers still while the stimuli are pressed against their skin. However, most stimulus properties are extracted through a combination of cutaneous and movement cues; this combination results in more than just a sum of kinaesthetic and tactile inputs, in the sense that only a complex integration of these cues allows the perception of objects in space and in relation to each other (Kaas et al. 2008) . This type of perception through touch is called haptic perception BIB001 . Haptic perception is the most natural form of perception through touch and is more related with free exploration procedures. Finally, the term ''tactual perception'' is a more generic concept and refers to all types of perception derived from cutaneous (tactile) and kinaesthetic (movement) cues and is used to describe overall perception by touch, regardless of experimental conditions and can be assumed as a synonym of touch. This literature review aims to contribute to the systematisation of information about touch by analysing the main variables manipulated within perceptual paradigms, namely the interactions of touch with other senses, the type of stimuli, the type of participants and the tactile exploratory conditions.