Excerpt: Inspired by the constructivist project of Piaget as presented in Construction du réel chez l’enfant (937), the aim of this chapter is to study the microand ontogenetic processes involved in the phenomenological constitution of space and perceived objects in humans. We shall not attempt to revisit the totality of Piaget’s project, but rather reexamine the initial structural and functional conditions with a view to reformulating the process of the construction of spatialized objects of perception. Our goal is to lend support to a radical constructivist thesis that holds, first, that the point of departure for an experience of the world is the lived body, and second, that the constitution of perceived objects is both constrained and made possible by the repertoire of actions available to the subject.

The strategies of action employed by a human subject in order to perceive simple 2-D forms on the basis of tactile sensory feedback have been modelled by an explicit computer algorithm. The modelling process has been constrained and informed by the capacity of human subjects both to consciously describe their own strategies, and to apply explicit strategies; thus, the strategies effectively employed by the human subject have been influenced by the modelling process itself. On this basis, good qualitative and semi-quantitative agreement has been achieved between the trajectories produced by a human subject, and the traces produced by a computer algorithm. The advantage of this “reciprocal modelling” option, besides facilitating agreement between the algorithm and the empirically observed trajectories, is that the theoretical model provides an explanation, and not just a description, of the active perception of the human subject.

Key words: active perception, computer modelling, sensory-motor invariants, visual tactile sensory substitution.

In information visualisation, zoomable user interfaces (ZUI) were developed in order to navigate in a big information space. They have an infinite space and allow the manipulation of infinite pans and zooms but the main drawback is the risk of getting lost in the information space. Understanding how a human being perceived the scale changes and how he is living this “zoomable” experience will help to avoid the user disorientation when he manipulate this kind of interfaces. While basing on ecological and enactive theories, we will try to bring some elements of responses in order to understand the navigation in ZUI.

The objective of this work concerns the design and the implementation of a zoomable interface implying the haptic modality. The initial postulate is that the zoom experience is not a natural, a direct experience, but supposes instrumentation and learning. In other words, the zoom experience is built by the appropriation of a technical substitution which makes it possible to modify the properties of the space-time flow; these properties which bind the subject to his (real or virtual) world are relational. To conceive this new interface, directly inspired from technologies known as of sensory substitution, we carried out a set of experiments allowing to define and to qualify the technical conditions and of use which favour the emergence of a perceptive experience of the zoom type. More generally, it concerns the proposition of more intuitive or immediate modes of instrumental interaction engaging explicitly the body in action.

In this study, we mentions the first results concerning the validity of the 2/3 power law for shapes explored by Tactos, a sensory substitution device.

Studies using the sensory substitution devices reveal that perceptive activity itself is embodied in a living body capable of movement and possessing its own spatial dimensions. To study the conditions of a prosthetic perception, we developed a minimal device, Tactos, which carries out a coupling between the pen of a graphics tablet and tactile sensory stimulators. This system allows subjects to explore virtual tactile pictures and is intended to give to blind people an access to computer graphics. We will present here experimental results regarding the different aspects of perception using this device.

Key words: sensory substitution, haptic and tactile perception, perception/action coupling.