Abstracts of the Psychonomic Society — Volume 4 — November 1999 40th Annual Meeting — November 18–21, 1999 — Los Angeles, California Posters 1–6 Thursday Evening Papers and Posters Presented at the 40th Annual Meeting of the Psychonomic Society Century Plaza Hotel, Los Angeles, California November 18–21, 1999 POSTER SESSION I other animal forms (e.g., birds, cats, horses). We will also report vari- California Showroom, Thursday Evening, 7:00–8:30 ations across these displays in the orientation specificity of sensitiv- ity, discussing possible implications for accounts of biological mo- •PERCEPTION • tion perception. (1) (4) Deficits of Complex Form Perception and Attention in a Patient Representing the “What” and the “Where” of Undetected With Partial Achromatopsia. RACHEL E. SHOUP, University of Change. IAN M. THORNTON, Nissan Cambridge Basic Research, California, Davis, & JAMIE A. MAZER & JACK L. GALLANT, & DIEGO FERNANDEZ-DUQUE, University of Oregon—Studies of University of California, Berkeley—Physiological studies in non- change blindness demonstrate that we are seldom aware of everything human primates suggest that cortical area V4 is important for the per- that is before our eyes. However, these studies may be telling us more ception of both color and form. Cells in V4 are also modulated by at- about the limits of visual awareness than about the limits of visual rep- tention. Because humans with V4 lesions typically exhibit severe resentation. Specifically, we have suggested that the explicit reports achromatopsia, most studies of these patients have focused on color used for most change blindness tasks underestimate the visual system’s vision. We assessed form vision and attention in a patient, A.R., with ability to represent change. In the current series of experiments we use upper left quadrant achromatopsia due to a small right occipito-tem- a simple change detection task coupled with a speeded orientation dis- poral (V4) infarct. Data were acquired in a series of threshold dis- crimination task to show that even when observers are subjectively un- crimination tasks performed concurrently in the four visual quadrants. aware of a change in orientation, such changes still affect their sub- Despite normal performance on motion and simple form stimuli, A.R. sequent orientation responses. These results provide new evidence showed marked deficits in the discrimination of non-Cartesian (cur- that visual representation of change can exist outside of awareness and vature) stimuli in his impaired quadrant. He also had difficulty judg- furthermore that these representations provide information about ing relative position and localizing low salience stimuli in this quad- “what” has changed as well as information about “where” a change rant, suggesting an impairment in attention. These data suggest that has taken place. human area V4 is functionally homologous to V4 in nonhuman pri- mates. (5) On the Inadequacies of Cognitive Explanation of Gamma Motion (2) Phenomena. WILLIAM C. SCHMIDT, SUNY, Buffalo—Several can- Time, Space, and Shape Distortions in Aperture Viewing. CAROL didate cognitive accounts have been put forward to explain the ex- YIN, California Institute of Technology—As an object moves behind pansion motion that is experienced when a probe item accompanies a multiple occluders, portions of the object are revealed while other por- previously visible prime (i.e., illusory line motion). Object level ac- tions become occluded. To see the object we must be integrating shape counts posit that the motion experienced is the result of processes that information across time and space, but how? The mechanisms of this transform one object view (the prime) into another later view (the spatiotemporal shape integration may be revealed by examining per- probe). However, this account fails to explain the data. For instance, ceptual distortions that occur during aperture viewing. Moving ob- they do not explain why motion can be experienced within the single jects anorthoscopically viewed through a slit often appear compressed presentation of an item (gamma motion), why multiple motion expe- (skinnier), but this compression is not homogeneous across the sur- riences can occur within probe items, why the direction of motion ex- face of the object. We showed observers ovals and quadrilaterals with perienced depends on spatial separation, why the effect breaks down different degrees of distortion and asked observers to judge whether for identifiable objects, and several other empirical results. Low-level the left or right half of the shape appeared more elongated. mechanistic approaches on the other hand fare better at explaining Preliminary results suggest that the amount of perceived distortion de- these results. A framework is presented that coordinates such find- pends on the contour curvature. However, another experiment using ings. four circles marking the vertices of an imaginary quadrilateral found that part of the distortion may be accounted for by a misperception of (6) time. A New, Object-Based Visual Illusion. ADAM C. G. COOPER & GLYN W. HUMPHREYS, University of Birmingham (sponsored by (3) Jane Riddoch)—In six experiments, normal participants were re- Visual Analysis of Human and Animal Biological Motion quired to compare the distance between features that grouped with the Displays. JEANNINE PINTO & MARGARET SHIFFRAR, Rutgers distance between features that did not group, and then to choose the University—Adults can effortlessly perceive a human form in a dis- wider or narrower distance. For all experiments, a strong response bias play of discrete elements (“point-lights”) moving as if attached to the was found indicating that the distance across the grouped features was major joints of an invisible person (Johansson, 1976). Given our great perceived as the wider by approximately 0.1º of visual angle, regard- sensitivity to these complex forms and the clear ecological value of less of item shape or of presentation type. We suggest that differences such sensitivity, some investigators suggest that the perception of in perceived distance reflects the use of distinct forms of spatial cod- these figures involves mechanisms specifically attuned to biological ing: “within object” and “between object,” in the terms introduced by motion. Does this sensitivity extend to nonhuman animal forms? In Humphreys and Riddoch (1994, 1995). In addition, the direction of a series of studies, we investigated the breadth of observers’ sensi- the illusion may be due to multiple factors: possibly higher neural res- tivity to biological motion. Previous findings suggest that the visual olution for within- versus between-object coding, or greater neural ac- system can perform global analyses in the extraction of human struc- tivation during selection of single, large objects versus during selec- ture from motion-carried information. We will report findings that tion across multiple, smaller objects, where activation level is related suggest that such analyses can also be deployed in the perception of to size of area selected. 1 Thursday Evening Posters 7–13 (7) rent study examined information processing (IP) with a psychologi- The Effect of Lateral Feature Displacement on Perceived Facial cal refractory period (PRP) paradigm. Typically, PRP paradigms uti- Attractiveness. JAY FRIEDENBERG & NICHOLAS FRIEDMANN, lize the second reaction time (RT2) of two closely spaced S–R pairs. Manhattan College—We investigated the influence of lateral dis- The current study investigated the effects of the second S–R pair on placement of facial features on perceived attractiveness. In the RT1. Logically, if the second S–R pair affected RT1, IP is not Experiment 1, the eyes, nose, and mouth of normal photographic fa- wholly serial. Subjects (nϭ24) were required to provide RTs under a cial images were displaced to the left and right in various combina- series of conditions, each manipulating a stage of IP. Results of the tions. The features were displaced by three pixels, corresponding to repeated measure ANOVA revealed a significant effect of the second approximately 1% of average facial width. Faces with two features S–R pair on the first RT. The results support a model that consists of moved to the left and one to the right were rated significantly less at- parallel processing until information demands require serial process- tractive than those with two features moved to the right and one to the ing. left. Experiment 2 sought to replicate this effect by performing the same displacements on symmetrical faces to control for amount of de- (11) viation from the vertical midline. The results showed that conditions Cognitive Demands of a Straight-Line Curve Tracing Task. with any featural displacements were now rated lower. This suggests MARK VAN SELST, San Jose State University, TONY RO- that sensitivity to featural deviation of this sort is more sensitive in DRIGUEZ, University of California, Irvine, & STACY GRANADA, symmetrical faces. San Jose State University—Ullman (1980) suggests that late percep- tual processing of a visual scene takes place through an assembly of •PATTERN PERCEPTION • basic visual operations that include mental rotation, curve tracing, and spatial indexing operators. Previous dual-task studies using the (8) psychological refractory period (PRP) paradigm have investigated the Response Categories and Interlevel Interference in Local–Global cognitive demands of mental rotation. These earlier studies have Processing. STEPHEN D. CHRISTMAN, University