Biomedical subjects

Alistair P Mapp

Publications and source records attributed to Alistair P Mapp.

4 recordsLinked to original sources

PubMed2006

The lost direction in binocular vision: the neglected signs posted by Wells, Towne, and LeConte.

Studies of vision have informed theories first in philosophy and then in psychology. Over the centuries, an increasing number of phenomena have been enlisted to refute or reinforce particular theories. Nowhere has this been more evident than in binocular vision. How we see a single world with two eyes is one of the oldest and most consistently studied topics in vision research. It has been discussed at least since the time of Aristotle and it has been examined experimentally since the second century, when Ptolemy defined lines of visual correspondence for the two eyes. Prior to Wheatstone's invention of the stereoscope in the 1830s, binocular vision had been studied in terms of visual directions. The stereoscope established distance (or depth) as well as direction as dimensions of binocular vision. Subsequently, depth rather than direction has been the principal concern of students of vision, and texts in English devoted to analyses of direction rather than depth have been neglected. We examine the experiments on binocular visual direction conducted by Wells before Wheatstone, and by Towne and LeConte after him, and discuss the reasons for their neglect.

History, 17th Century↗

PubMed2005

The cyclopean eye is relevant for predicting visual direction.

Wells-Hering's laws summarize how we process direction and predict that monocular stimuli appear displaced with respect to the viewer, but not with respect to other seen objects [Erkelens, C. J., & van Ee, R. (2002). The role of the cyclopean eye in vision: sometimes inappropriate, always irrelevant. Vision Research 42, 1157-1163] criticized this view and claimed that there is no perceptual displacement of these stimuli. We challenge their claim and improve on shortcomings of past studies. LEDs were monocularly presented to the observers, without their knowledge of which eye was being stimulated. Viewing distance was 9-10 cm; fixation distance was 30 cm. Observers reported the perceived relative and absolute directions of monocular stimuli. Our results are consistent with Wells-Hering's laws.

Awareness↗

PubMed2003

What does the dominant eye dominate? A brief and somewhat contentious review.

We examine a set of implicit and explicit claims about the concept of eye dominance that have been made over the years and note that the new literature on eye dominance does not reflect the old literature from the first half of the last century. We argue that the visual and oculomotor function of the dominant eye--defined by such criteria as asymmetry in acuity, rivalry, or sighting--remains unknown and that the usefulness of the concept for understanding its function is yet to be determined. We suggest that the sighting-dominant eye is the eye used for monocular tasks and has no unique functional role in vision.

Dominance, Cerebral↗

PubMed2002

The cyclopean eye in vision: the new and old data continue to hit you right between the eyes.

We argue against recent claims by Erkelens and van Ee (Vision Res., in press) and by Erkelens (Vision Res. 40 (2000) 2411) that "the concept of the cyclopean eye is em leader always irrelevant as far as vision is concerned" (p. 1157) [corrected] and that "perceived direction during monocular viewing is based on the signals of the viewing eye only" (p. 2411), respectively. In Experiment 1, we presented a pair of small lights on a visual axis and measured the absolute visual direction of the near light with reference to different parts of the face. The near light appeared in front of the bridge of the nose or very near it, contrary to what was expected from Erkelens and van Ee's claim that monocular stimuli are seen in their correct locations. In Experiment 2, we replicated Erkelens' experiments with measurements of phoria and analyses of eye movements. The results confirmed his finding that the cyclopean illusion occurred rarely in the monocular condition, but our phoria and eye movement data provided the basis for a very different interpretation. Our data show that the oculomotor signal in his particular monocular condition was considerably weaker than in his binocular condition; therefore, the rarity of the monocular cyclopean illusion is not surprising. Moreover, since both claims above are based on an over-generalization of the results of Erkelens' study, neither claim is persuasive.

Adult↗