We assessed age differences in the ability to resolve competition for figural status in stationary displays using small, enclosed, symmetrical silhouettes that participants classified as depicting "novel'' or "familiar'' shapes. The silhouettes were biased such that the inside was perceived as the shaped figure, and the outside was perceived as a shapeless ground. The critical manipulation was whether a portion of a meaningful object was suggested on the outside of the border of some of the novel silhouettes but not others M(+)Ground and M-Ground novel silhouettes, respectively). This manipulation was intended to induce greater inhibitory competition for figural status from the groundside in M(+)Ground silhouettes than M(-)Ground silhouettes. In previous studies, young adults classified M(+)Ground silhouettes as "novel'' faster than M(-)Ground silhouettes (Trujillo, Allen, Schnyer, & Peterson, 2010), suggesting that young adults may recruit more inhibition to resolve figure-ground when there is more competition. We replicated this effect with young adults in the present study, but older adults showed the opposite pattern and were less accurate in classifying M(+)Ground than M(-)Ground silhouettes. These results extend the evidence for inhibitory deficits in older adults to figure assignment in stationary displays. The (M(+)Ground - M(-)Ground) RT differences were evident in observers' longest responses, consistent with the hypothesis that inhibitory deficits are evident when the need for inhibition is substantial.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Psychology." Includes bibliographical references (p. 25-26).

Traditional theories of vision assume that object segregation occurs before access to object memories. Yet, behavioral evidence shows that familiar configuration is a prior for segregation, and electrophysiological experiments demonstrate these memories are accessed rapidly. A behavioral index of the speed of access is lacking, however. Here we asked how quickly behavior is influenced by object memories that are accessed in the course of object segregation. We investigated whether access to object memories on the groundside of a border can slow behavior during a rapid categorization task. Participants viewed two silhouettes that depicted a real-world and a novel object. Their task was to saccade toward the real-world object as quickly as possible. Half of the nontarget novel objects were ambiguous in that a portion of a real-world object was suggested, but not consciously perceived, on the groundside of their borders. The rest of the nontargets were unambiguous. We tested whether saccadic reaction times were perturbed by the real-world objects suggested on the groundside of ambiguous novel silhouettes. In Experiments 1 and 2, saccadic reaction times were slowed when nontargets were ambiguous rather than unambiguous. Experiment 2 set an upper limit of 190 ms on the time required for object memories in grounds to influence behavior. Experiment 3 ruled out factors that could have produced longer latencies other than access to object memories. These results provide the first behavioral index of how quickly memories of objects suggested in grounds can influence behavior, placing the upper limit at 190 ms.

Nelson and Palmer (2007) concluded that figures/figural properties automatically attract attention, after they found that participants were faster to detect/discriminate targets appearing where a portion of a familiar object was suggested in an otherwise ambiguous display. We investigated whether these effects are truly automatic and whether they generalize to another figural property-convexity. We found that Nelson and Palmer's results do generalize to convexity, but only when participants are uncertain regarding when and where the target will appear. Dependence on uncertainty regarding target location/timing was also observed for familiarity. Thus, although we could replicate and extend Nelson and Palmer's results, our experiments showed that figures do not automatically draw attention. In addition, our research went beyond Nelson and Palmer's, in that we were able to separate figural properties from perceived figures. Because figural properties are regularities that predict where objects lie in the visual field, our results join other evidence that regularities in the environment can attract attention. More generally, our results are consistent with Bayesian theories in which priors are given more weight under conditions of uncertainty.

M.A.University of the Witwatersrand, Faculty of Humanities (Fine Arts), 2012 / The ‘Bath Series’ (1983-1988) of Jasper Johns shows the artist’s meditation on his oeuvre of the past thirty years, and the examples of his previous works demonstrate his interest in instabilities of visual perception. The latter are activated when the viewer’s expectation to see conventional representational strategies are destabilized, and figure/ground pictorial space, particularly, becomes ambiguous. This first recorded academic study focusing exclusively on the series as a unit, discovers that figure/ground switching, an ‘Ur-Gestalt’ (Gandelman 1989: 209), appears to be a core energy motivating ambiguous pictorial space in Johns’ art, and constitutes the theoretical component of the research. The practical component is a site specific installation which shows some visual and verbal processes and meditates on the perpetual interaction between the eye and the mind, which is a fundamental concern of Johns (Varnedoe 1996b: 245, 257), as well as of myself. The work invites viewers to experience destabilized conventional visual perceptions and to explore, as Johns said, ‘something new’ (Varnedoe 1996a: 17).

Codons are simple primitives for describing plane curves. They thus are primarily image-based descriptors. Yet they have the power to capture important information about the 3-D world, such as making part boundaries explicit. The codon description is highly redundant (useful for error-correction). This redundancy can be viewed as a constraint on the number of possible codon strings. For smooth closed strings that represent the bounding contour (silhouette) of many smooth 3D objects, the constraints are so strong that sequences containing 6 elements yield only 33 generic shapes as compared with a possible number of 15, 625 combinations.

Vision provides the primary means by which many animals distinguish foreground objects from their background and coordinate locomotion through complex environments. The present thesis focuses on mechanisms within the visual system that afford figure-ground segregation and self-motion perception. These processes are modeled as emergent outcomes of dynamical interactions among neural populations in several brain areas. This dissertation specifies and simulates how border-ownership signals emerge in cortex, and how the medial superior temporal area (MSTd) represents path of travel and heading, in the presence of independently moving objects (IMOs). Neurons in visual cortex that signal border-ownership, the perception that a border belongs to a figure and not its background, have been identified but the underlying mechanisms have been unclear. A model is presented that demonstrates that inter-areal interactions across model visual areas V1-V2-V4 afford border-ownership signals similar to those reported in electrophysiology for visual displays containing figures defined by luminance contrast. Competition between model neurons with different receptive field sizes is crucial for reconciling the occlusion of one object by another. The model is extended to determine border-ownership when object borders are kinetically-defined, and to detect the location and size of shapes, despite the curvature of their boundary contours. Navigation in the real world requires humans to travel along curved paths. Many perceptual models have been proposed that focus on heading, which specifies the direction of travel along straight paths, but not on path curvature. In primates, MSTd has been implicated in heading perception. A model of V1, medial temporal area (MT), and MSTd is developed herein that demonstrates how MSTd neurons can simultaneously encode path curvature and heading. Human judgments of heading are accurate in rigid environments, but are biased in the presence of IMOs. The model presented here explains the bias through recurrent connectivity in MSTd and avoids the use of differential motion detectors which, although used in existing models to discount the motion of an IMO relative to its background, is not biologically plausible. Reported modulation of the MSTd population due to attention is explained through competitive dynamics between subpopulations responding to bottom-up and top- down signals.

Little is known about how healthy aging impacts figure-ground (FG) perception, which is critical in organizing complex visual input into coherent figures. Inhibitory-suppression is thought to be critical in resolution between competing FG interpretations. Given the age-related changes to inhibitory cortical mechanisms, my thesis investigated the hypothesis that processes underlying FG organization are impaired in aging. We explored the effects of age on the convexity context effect (CCE): the tendency to perceive convex regions as figural [i.e., P(Convex=Figure)] increases with surrounding convex and concave regions. In Chapter 2, we observed that adding context by increasing region number, increased P(Convex=Figure) in younger and older observers, but this CCE was significantly reduced in older adults. Reducing competition between perceptual interpretations by heterogeneously colouring convex regions, thereby invalidating the alternative {Concave=Figure} stimulus interpretation, greatly increased P(Convex=Figure) in older observers. These results supported the notion that aging impairs FG organization, particularly in relatively high competition contexts. In Chapter 3, we explored the possibility that reduced presumption of depth in our stimuli might explain the reduced the CCE in older observers by adding texture motion to region fills consistent with depth in the stimulus. The results were inconsistent with the hypothesis, but supported the reduced inhibitory-suppression hypothesis of the age effect. In Chapter 4, we explored the neural activation associated with the processing mechanisms underlying the resolution of FG competition. The results indicated that the N250 in younger observers but not older observers is sensitive to high vs. low competition contexts. Furthermore, individual differences in this N250-competition effect were correlated with the behavioural effect of competition. Our findings are consistent with the hypothesis that the processing underlying FG organization is impaired in senescence, which may stem from reduced efficacy of the neural architecture supporting this ability. Various implications of this work are discussed. / Dissertation / Doctor of Philosophy (PhD)

The nature of figure-ground relationships and their potential for use as a tool for architectural composition was investigated through the design of a winery. Included in the winery were facilities accomodating both the production and consumption of wine. These programmatic elements were used as guides for the development of multiple figure-ground relationships at a variety of scales. In addition, the dialogue between different figures as well as the careful development of the backdrop surfaces were topics of study. Several design strategies were employed to create relationships between figure elements and their backdrops, including the insertion of volumes into and through one another, the careful development of material and surface, and light. From this work, as well as previous projects, several key findings can now be articulated concerning the potential use of figure-ground relationships in the development of a work of architecture. These include the need to optimize the proportion of figure(s) relative to a given background and the key role that the disposition of figures relative to one another plays in the development of a meaningful figure-ground relationship. / Master of Architecture

My Trip to Notan charts my own journey from the rawness and acceptance of multiple life losses into understanding, and finally, renewal. The key result of this project is a prototype book, a 48-page digital Print-On-Demand (POD) publication, which also includes a DVD that inserts into book’s back and features live demonstrations, interviews and other segments related to the book. Additionally, the body of work from which the book was gleaned was presented at the thesis exhibition. Ultimately, My Trip to Notan is a sketch of my understanding of the framework that threads through design, physics and philosophy, inspired by the simplicity of the ancient art of Notan, and upon my own fragmentary observations gathered from the journey. My hope was to reveal some sense of the pulse that drives the inquiry, rather than the suggestion of any sort of destination.