In the present study, we conducted two experiments (Experiment 1: 35 participants, M = 29; SD = 8.4; Experiment 2: 36 participants, M = 25; SD = 6.1) with the intention to explore whether underlying perceptual grouping operations and illusory form perception generate dissociable priming effects when Kanizsa-like figures are presented as primes and the rotated inducers as controls under conditions of restricted awareness. Using five different stimulus onset asynchronies (SOA conditions, Experiment 1: 27, 40 and 53 ms; Experiment 2: 27, 80 and 227 ms), we displayed masked illusory and groping primes that could be congruent or incongruent in their orientation with subsequent probe stimuli (vertical vs. horizontal). We found significant priming effects in both Experiment 1 and 2 (p < .001, η2p = .31 and p = .016, η2p = .16, respectively), but, crucially, no significant priming differences between illusory and grouping primes across SOA conditions. Overall, our results are important in showing that a dissociation of the percept generated by the grouping of the inducers from that generated by the illusory form is crucial in the study of illusory form perception under conditions of restricted awareness. In addition, they provide further evidence of perceptual organization operations occurring under very restrictive awareness conditions.

This study examines the influence of the relative strength of grouping principles on interactions between the intrinsic principle of proximity and the extrinsic principle of common region in the process of perceptual organization. Cooperation and competition between intrinsic and extrinsic principles were examined by presenting the principle either alone or conjoined with another principle. The relative grouping strength of the principles operating alone was varied in two different groups of participants so that it was similar for one group and very different for the other group. Results showed that, when principles acting alone had different strengths, the grouping effect of the strongest principle was similar to that of the cooperation condition, and the effect of the weakest principle was similar to that of competing conjoined principles. In contrast, when the strength of principles acting alone was similar, the effect of conjoined cooperating principles was greater than that of either principle acting alone. Moreover, the effect of conjoined competing principles was smaller than that of either principle operating alone. Results show that cooperation and competition between intrinsic and extrinsic principles are modulated by the relative grouping strength of principles acting alone. Furthermore, performance in these conditions could be predicted on the basis of performance in single-principle conditions.

The watercolor illusion is a color spreading effect at long-range diffusing from a thin colored contour juxtaposed to a chromatic one of higher contrast and a object-hole effect across a large area (Pinna, 1987; Pinna et al., 2001, 2003; Pinna & Reeves, 2006). The watercolored figure appears evenly colored by an opaque light veil of chromatic tint (coloration effect), with a clear surface color property spreading from the lighter contour. At the same time, the watercolored figure manifests a strong figure-ground organization and a solid figural appearance comparable to a bas-relief illuminated from the top (object-hole effect). It appears similar to a rounded surface segregated in depth, which extends out from the flat surface. The complementary region appears as a hole or empty space. The phenomenal properties of coloration and object-hole effects raise some questions. Can the two effects be considered relatively independent? Under what conditions can a possible dissociation occur? How does the dissociation of one effect, say the coloration, influence the object-hole effect and vice versa? To answer these questions two new effects related to the watercolor illusion were psychophysically studied: (1) the “uneven watercolor,” based on a modified watercolor figure without volumetric and three-dimensional properties but with a strong coloration effect and (2) the “watercolor surface capture,” where oblique lines within a watercolor figure appear bulging, curved in depth and segregated from those that are perceived as placed in the background or perceived through holes. The results of two experiments suggest that the coloration effect can be dissociated from the object-hole one. These results are discussed in the light of a simple summation hypothesis of the underlying effects composing the whole figurality. This hypothesis can suggest further investigation both in the phenomenal and in the neurophysiological domain.

Amodal completion is the most common form of visual completion occurring when portions of an object are hidden, due to their occlusion behind another object (Michotte, 1951). Just as a shape is completed amodally behind another occluding shape, so is a color behind another occluding color or behind a lighting: a bright light reflected by a three-dimensional object. Four possible phenomenal combinations related to the amodal completion of color are shown: amodal or modal coloration or discoloration. Purposes of four experiments were: (1) to demonstrate the amodal completion of color under different stimulus conditions and under chromatic and achromatic conditions and (2) to extract the general principles ruling the amodal completion of color: “which, among many, is the color that completes amodally?” and, consequently, “which is the region of an object that determines its color?” The results showed the effectiveness of the amodal completion of color and that chromatic and achromatic conditions reveal different results. Four general principles of the amodal completion of color, useful to understand the more general problem of phenomenal organization of color, are suggested.

The concept of locally specialized functions dominates research on higher brain function and its disorders. Locally specialized functions must be complemented by processes that coordinate those functions, however, and impairment of coordinating processes may be central to some psychotic conditions. Evidence for processes that coordinate activity is provided by neurobiological and psychological studies of contextual disambiguation and dynamic grouping. Mechanisms by which this important class of cognitive functions could be achieved include those long-range connections within and between cortical regions that activate synaptic channels via NMDA-receptors, and which control gain through their voltage-dependent mode of operation. An impairment of these mechanisms is central to PCP-psychosis, and the cognitive capabilities that they could provide are impaired in some forms of schizophrenia. We conclude that impaired cognitive coordination due to reduced ion flow through NMDA-channels is involved in schizophrenia, and we suggest that it may also be involved in other disorders. This perspective suggests several ways in which further research could enhance our understanding of cognitive coordination, its neural basis, and its relevance to psychopathology.