AbstractsPsychology

In everyday life, we frequently explore surfaces with our fingertips to capture aspects of their physics, such as texture or toughness. Furthermore, such explorations are often accompanied by a perception of (un)pleasantness. It is therefore of interest to investigate the relationship that could exist between the sensation of pleasantness and the physical attributes of explored surfaces. Typically, the sensation of pleasantness in touch is indirectly assessed, generating ordinal data. Such data lack fundamental psychometric properties that are essential to carry out objective and quantitative analyses. To address this problem, probabilistic measurement models (e.g. Rasch model) can be used to establish linear, unidimensional and invariant scales from ordinal scores by locating subjects and items along a single underlying scale. In this thesis, the Rasch Model has been used to establish a basis for future investigations on pleasantness perception at fingertip level. Indeed, a unidimensional, linear and invariant Pleasant Touch Scale has been developed, which classifies 37 different everyday life materials according to their pleasantness levels. The pleasantness levels suggested that the pleasantness perception, occurring during active surface exploration, had a certain correlation with aspects of the microgeometry of the surfaces as well as with the frictional properties arising when sliding fingers on them. These indications were thoroughly investigated during active and passive tactile surface exploration experiments. Moreover, the effect of surface temperature on the perception of pleasant touch was studied. In conclusion, all studies indicated that surface topography and frictional forces resulting from surface exploration are important factors for pleasantness sensation during touch with a fingertip. (MOTR - Sciences de la motricité)  – UCL, 2014