Toucher et ressentir les stimuli vibrotactiles complexes

Human beings are capable of interacting with their environment via the sense of touch. In addition to allow the discrimination between the many objects in our daily lives, the sense of touch provides a very powerful means of eliciting and modulating human emotion. Touch is crucial for our survival and well-being, particularly through the pleasant or unpleasant evaluation of objects and interpersonal interactions. Among the physical characteristics of tactile contact influencing tactile perception, vibrations play an essential role in the discrimination of textures and thus aesthetic preferences. In the case of vibration derived from simple stimuli, the impact of vibration's most significant characteristics (frequency and amplitude) on haptic perception has been studied extensively. However, vibrations generated by complex interactions (such as grasping, sliding or tapping) involve a variety of frequencies and amplitudes that remains under-investigated so far. This thesis focuses on the detection of complex vibrations by humans as they correspond to the most encountered ones -or as they have higher ecological validity. Likewise, knowledge about appreciation of complex vibrotactile contacts remains to be explored to clarify the mechanisms underlying the pleasantness of touch. The present thesis explores the mechanisms of discrimination and hedonic assessment of complex stimuli through several psychophysical studies. An initial exploratory study, in which the goal was to recreate a realistic sensation, motivated the research questions of this thesis. It highlighted the challenge of pinpointing the key characteristics individuals use to perceive tactile sensations encountered in daily life. Following that, the thesis presents an empirical study that analyzes the vibrotactile cues of complex signals influencing tactile discrimination. Psychophysical models were implemented to better understand the results obtained. Finally, in order to gain a better understanding of the mechanisms by which vibrations are integrated into the hedonic evaluation of a pleasant contact, a study was conducted to understand the contribution of tactile receptors underpinning tactile pleasantness. To do that, the study compared a vibrotactile illusion of motion with the perception of a real stroke. Our results pave the way for a more in-depth investigation of the tactile pleasantness of complex vibrotactile signals, integrating the findings of the aforementioned studies. The summary of all works are brought altogether in the final chapter of this thesis.