Perception

A comparison was made between two measures of visual functioning in a dynamic context that required the resolution of moving targets. Performance obtained on a traditional task of dynamic visual acuity, which involves the determination of the smallest target that can be resolved at a given target velocity, was compared with that obtained with an alternative task that essentially reverses the independent and dependent variables. Generally similar patterns of results were obtained across the two procedures, but the alternative procedure appears to offer several advantages such as greater ease of administration, improved precision of measurement, and more-direct assessment of underlying channel activity. The recommended use of the new procedure in future work involving dynamic acuity as well as particular variables that should be carefully controlled in such work (eg target duration and target size) are discussed.

Although we can selectively attend to colour, preknowledge of the location of a target has been shown to facilitate visual selection more than preknowledge of the target colour. Here the effects of peripheral flash cues and central colour cues were compared in three experiments. A novel colour-cuing procedure was used in which the target location was designated in advance by colour. Since variations in stimulus eccentricity and density similarly affected performance in both conditions, the colour cues presumably also made it possible to direct attention quickly to the target location. Thus, the colour cues in this study were analogous to symbolic location cues, such as central digits. Moreover, even though peripheral colour information was provided in experiments 1 and 2 only 84 ms before stimulus array, ie at the same time as the onset cue was flashed on, the effect of colour cues was comparable to that of peripheral flashes. This is a surprising finding given previous data on the time to interpret symbolic location cues and to allocate attention to the target location.

Two experiments were performed to examine how the subjective balance of a painting is created by its structural features and to determine if balance influences the way people look at paintings. Stimuli consisted of sixteen reproductions of twentieth-century paintings varying in artistic style and a reconstructed less-balanced version of each. Participants in experiment 1 determined the location of the balance center of each composition, assigned ‘weights’ to the pictorial features which contributed to the location of the balance center, and rated the picture for balance. It was found that design and museum professionals and individuals untrained in the visual arts were in good agreement as to the structural framework underlying the balance organization of a painting. For all participants, disruption of the balanced organizations of the original compositions led to reliable shifts in the location of the perceived balance centers of the originals compared with their less-balanced perturbations. Additionally, it was observed that particular features as such were not the origin of the balance phenomenon; rather, judgments concerning the balance structure and its center were dependent on the global integration of information across a wide area of the display field, but especially from its central region. Last, the subtle changes in balance structure between versions resulted in lower ratings of balance being assigned to the less-balanced perturbations by the design professionals only; the other two participant groups evaluated overall balance of the versions as comparable. In experiment 2, eye movements of a different group of untrained individuals were recorded as they performed similar tasks on the art stimuli. It was found that disruption of the balance structure of the original representational but not abstract compositions resulted in different regions of the original and perturbed versions being visually explored. Findings of both experiments are related to theoretical notions of balance.

While the perceptual substratum of interceptive tasks has been largely investigated, no studies report unequivocal evidence for the use of a specific source of information. This result can be interpreted differently according to the perceptual theory considered. In the framework of directed perception this result would illustrate the flexibility of our perceptual system performing the same task in different ways under different circumstances. This paper is designed to formalise, for each category of invariant considered (ie temporal, spatial, and spatiotemporal), a binocular invariant leading to specification of the same physical quantity as a monocular invariant identified in the literature. This formalisation illustrates a redundancy of monocular and binocular invariants that is particularly appealing from the viewpoint of directed perception.