Biomedical subjects

Stephen Palmisano

Publications and source records attributed to Stephen Palmisano.

6 recordsLinked to original sources

PubMed2006

Illusory scene distortion occurs during perceived self-rotation in roll.

We report a novel illusory distortion of the visual scene, which became apparent during both: (i) observer rotation inside a furnished stationary room; and (ii) room rotation about the stationary observer. While this distortion had several manifestations, the most common experience was that scenery near fixation appeared to sometimes lead and other times lag more peripheral scenery. Across a series of experiments, we eliminated explanations based on eye-movements, distance misperception, peripheral aliasing, differential motion sensitivity and adaptation. We found that these illusory scene distortions occurred only when the observer perceived (real or illusory) changes in self-tilt and maintained a stable fixation.

Adult↗

PubMed2005

Effect of decorrelation on 3-D grating detection with static and dynamic random-dot stereograms.

Three experiments examined the effects of image decorrelation on the stereoscopic detection of sinusoidal depth gratings in static and dynamic random-dot stereograms (RDS). Detection was found to tolerate greater levels of image decorrelation as: (i) density increased from 23 to 676 dots/deg2; (ii) spatial frequency decreased from 0.88 to 0.22 cpd; (iii) amplitude increased above 0.5 arcmin; and (iv) dot lifetime decreased from 1.6s (static RDS) to 80 ms (dynamic RDS). In each case, the specific pattern of tolerance to decorrelation could be explained by its consequences for image sampling, filtering, and the influence of depth noise.

Adult↗

PubMed2005

Visual perception of touchdown point during simulated landing.

Experiments examined the accuracy of visual touchdown point perception during oblique descents (1.5 degrees -15 degrees ) toward a ground plane consisting of (a) randomly positioned dots, (b) a runway outline, or (c) a grid. Participants judged whether the perceived touchdown point was above or below a probe that appeared at a random position following each display. Although judgments were unacceptably imprecise and biased for moving dot and runway displays, accurate and unbiased judgments were found for grid displays. It is concluded that optic flow per se does not appear to be sufficient for a pilot to land an airplane and that the systematic errors associated with optic flow under sparse conditions may be responsible for the common occurrence of landing incidents in so-called "black hole" situations.

Adult↗

PubMed2004

Jitter and size effects on vection are immune to experimental instructions and demands.

Both coherent perspective jitter and explicit changing-size cues have been shown to improve the vection induced by radially expanding optic flow. We examined whether these stimulus-based vection advantages could be modified by altering cognitions and/or expectations about both the likelihood of self-motion perception and the purpose of the experiment. In the main experiment, participants were randomly assigned into two groups-one where the cognitive conditions biased participants towards self-motion perception and another where the cognitive conditions biased them towards object-motion perception. Contrary to earlier findings by Lepecq et al (1995 Perception 24 435-449), we found that identical visual displays were less likely to induce vection in 'object-motion-bias' conditions than in 'self-motion bias' conditions. However, significant jitter and size advantages for vection were still found in both cognitive conditions (cognitive bias effects were greatest for non-jittering same-size control displays). The current results suggest that if a sufficiently large vection advantage can be produced when participants are expecting to experience self-motion, it is likely to persist in object-motion-bias conditions.

Adult↗

PubMed2003

Coherent perspective jitter induces visual illusions of self-motion.

Palmisano et al (2000 Perception 29 57-67) found that adding coherent perspective jitter to constant-velocity radial flow improved visually induced illusions of self-motion (vection). This was a surprising finding, because unlike pure radial flow, this jittering radial flow should have generated sustained visual--vestibular conflicts--previously thought to always reduce/impair vection. We attempted to ascertain the essential stimulus features for this jitter advantage for vection by examining three novel types of jitter display. While adding incoherent jitter to radial flow was found to impair vection, adding coherent non-perspective jitter had little effect on this subjective experience (contrary to the notion that jitter improves vection by reducing adaptation to radial flow). Importantly, we found that coherent perspective jitter not only improves the vection induced by radial flow, but it also appears to induce modest vection by itself (demonstrating that vection can still occur when there is an extreme mismatch between actual and expected vestibular activity). These results suggest that the previously demonstrated advantage for coherent perspective jitter was due (in part at least) to jittering vection combining with forwards vection in depth to produce a more compelling overall vection experience.

Adolescent↗

PubMed2002

Consistent stereoscopic information increases the perceived speed of vection in depth.

Previous research found that adding stereoscopic information to radially expanding optic flow decreased vection onsets and increased vection durations (Palmisano, 1996 Perception & Psychophysics 58 1168-1176). In the current experiments, stereoscopic cues were also found to increase perceptions of vection speed and self-displacement during vection in depth--but only when these cues were consistent with monocularly available information about self-motion. Stereoscopic information did not appear to be improving vection by increasing the perceived maximum extent of displays or by making displays appear more three-dimensional. Rather, it appeared that consistent patterns of stereoscopic optic flow provided extra, purely binocular information about vection speed, which resulted in faster/more compelling illusions of self-motion in depth.

Adolescent↗