Inverting a face impairs perception of its features and recognition of its identity. Whether faces are special in this regard is a current topic of research and debate. Kanizsa studied the role of facial features and environmental context on perception of the emotion and identity of upright and inverted faces. He found that observers are biased to interpret faces in a retinal coordinate frame, and that this bias is readily overruled by increased realism of facial features, but not easily overruled by environmental context. An additional factor contributing to a retinal coordinate frame interpretation may be the ambiguous nature of the face stimuli. Since the expressions are interpretable both upright and inverted, this may activate endogenous attention process for faces. We present visual search and change-blindness experiments which explore how inversion, negation, and facial emotion affect visual attention to static faces. We find that attention to faces is impaired by inversion and negation. We also find that the parts of the face which receive greater attention can be influenced by the emotional expression of the face. We propose to extend these experiments to dynamic faces. To this end, we develop a theory of the visual representation of dynamic faces, in which faces are represented by classes of "spacetime fragments"--moving regions of the face with high informational content. We then present ideas for several future experiments which are motivated by the spacetime fragment theory, and which should serve to constrain its further development.

Collinearity or correspondence between the contours of the inducing figure to allow ‘contour continuation’ or ‘figure completion were, according to G. Kanzsa, the necessary conditions for producing anomalous surfaces or contours. Since Kanizsa’s early work various hypotheses have been advanced to explain the phenomenon, but very few examples of anomalous contours that do not satisfy the above conditions have been reported.

Some years ago it was reported ( Zanforlin and Vallortigara, 1990) that when two small white discs (1 cm in diamter) are set on a larger black disc in slow rotation, the two discs, after some observation time, will appear as the extremities of a rigid cylinder displaced in depth. The surface of the cylinder, under dim illumination, appears as a whitish transparent surface.

However, when the two discs are substituted by a circle and a semi-circle ( as: C O ) of the same size, a clear anomalous contour appears to form the cylinder, even under clear light conditions and when the colours are reversed; i.e. black circles on white disc. The anomalous contours are not apparent when the configuration is stationary. At that time the two extremities of the semi-circle were interpreted as a “tendency” to complete the circle, so that, although mimimal, the conditions for an anomalous surface were present. I will now demonstrate how the anomalous contours of a stereokinetic cylinder can be obtained even without the “interruption” of the lines in the semicircle.

The relationship between the anomalous contours of the stereokinetic cylinder and the vitreous transparency of the surface of the cylinder formed by the two small discs above mentioned, will be discussesd as well as their relation to the general theories of anomalous surfaces.

[References: Zanforlin, M. Vallortigara, G. (1990) The magic wand: a new stereokinetic anomalous surface, Perception, 19: 447-457.]

The concept of invariants has been central for Gestalt psychology as well as for Gibson's Ecological Psychology. Theoretical discussions about the role invariants play in perception have been hamperd by different interpretetations of the concept (see Cutting 1979).

Starting form the notion that visual perception is always dependent on the interaction of object and position perception, I show that the ambiguity of Praegnanz (Kanisza & Luccio) mirrors exactly these complementary aspects of perception and makes necessary a conception of invariance which is topological, however, with geometrical constraints.

At the level of cognitive studies, it appears necessary now to extend the conditions of predicative activity, as defined by Quine, by admitting the necessary utilization of certain abstract concepts in addition to the merely combinatorial concepts referring to symbols. For this purpose we must count as abstract those concepts that do not comprise properties and relations of concrete objects (the inspectable evidence) but which are concerned with thought constructions and, in general, with the articulation of the intellectual tools of invention and control proper to the human mind.

The utilization, at the semantic level, of abstract concepts, the possibility of referring to the sense of symbols and not only to their combinatorial properties, the possibility of picking up the deep information existing in things, the extended use of functional models within a dynamic context characterized by the presence of precise forms of co-evolution, open up new horizons at the level of cognitive studies.

In the thirties Goedel suggested that mental procedures might extend beyond mechanical procedures because there may be finite, non-mechanical procedures that make use of the meaning of the terms. He spoke about "the beginnings of a science which claims to possess a systematic method for such clarification of meaning, and that is the phenomenology founded by Husserl" . With respect to  cognitive science ,Goedel's suggestions constitute now a precise guideline for the advancement of research.