Oman York Conference (2001 in press)11/2/01 of the effect, with group average being about 6 degrees. The effect diminished with larger frame tilts, probably because the square was perceived as an upright diamond, so the diagonals became the perceptually dominant axes. Ebenholtz(1977) later showed that larger frames induced effect. Singer(1970)and Howard and Childerson(1994)extended this result by having p& greater rod tilt than smaller ones, showing that field of view is important in producing a frame gravitationally upright observers view the interior of an unfurnished cubic chamber. The Sv was consistently deviated towards the nearest axis of room symmetry, either the floor-ceiling-wall directions. or the room diagonals 4.3 Visual Polarity Effects. Howard(1982)noted that in daily life there is a class of common objects that we almost always encounter in a " upright " orientation with respect to gravity Examples include tables, chairs, rugs, doors, houses, trees, cars, or human figures. These objects all have a readily identifiable""and"bottom", with mass distributed approximately equally on either side of an axis of symmetry, so they do not tip over. Howard refers to these as intrinsically polarized"objects. Their relative orientation of conveys information about the direction of gravity, and can help disambiguate frame cues. Many other objects such as coins, pencils, books, etc. which are not usually seen in a consistent gravitational orientation are described as" non-polarized In the context of orientation in weightlessness, it is important to note that large surfaces including those which extend beyond the immediate field of view, establish the major planes of visual space, but if their visual identity is ambiguous, they can provide only frame cues. w believe that in weightlessness the perceptual floor/ceiling/wall ambiguity of such surfaces is resolved by the relative orientation of the surface with respect to the body axis, or polarized visual details on the surface itself To experimentally measure object polarity, Hu, Howard and Palmisano(1999)had observers lying supine on a an elevated bed (Figure 12), look upward into a wide mirror angled at 45 degrees so they saw a left-right reversed view of the laboratory beyond the head of the bed. If the scene was a blank wall, observers perceived It iling. However when intrinsically polarized objects were placed in view, the Figure 12. Mirror bed apparatus of Hu, et al (used with observers perceived their heads as upright, and their bodies tilted by an amount which varied depending on the characteristics of the objects in the scene. The extent of perceived body tilt was used as a measure of visual polarity. Polarized objects placed in the background appearedOman York Conference (2001 in press) 11/2/01 Page 12 of the effect, with group average being about 6 degrees. The effect diminished with larger frame tilts, probably because the square was perceived as an upright diamond, so the diagonals became the perceptually dominant axes. Ebenholtz (1977) later showed that larger frames induced greater rod tilt than smaller ones, showing that field of view is important in producing a frame effect. Singer (1970) and Howard and Childerson (1994) extended this result by having gravitationally upright observers view the interior of an unfurnished cubic chamber. The SV was consistently deviated towards the nearest axis of room symmetry, either the floor-ceiling-wall directions, or the room diagonals. 4.3 Visual Polarity Effects. Howard (1982) noted that in daily life, there is a class of common objects that we almost always encounter in a “upright” orientation with respect to gravity. Examples include tables, chairs, rugs, doors, houses, trees, cars, or human figures. These objects all have a readily identifiable “top” and “bottom”, with mass distributed approximately equally on either side of an axis of symmetry, so they do not tip over. Howard refers to these as “intrinsically polarized” objects. Their relative orientation of conveys information about the direction of gravity, and can help disambiguate frame cues. Many other objects such as coins, pencils, books, etc. which are not usually seen in a consistent gravitational orientation are described as “non-polarized”. In the context of orientation in weightlessness, it is important to note that large surfaces, including those which extend beyond the immediate field of view, establish the major planes of visual space, but if their visual identity is ambiguous, they can provide only frame cues. We believe that in weightlessness the perceptual floor/ceiling/wall ambiguity of such surfaces is resolved by the relative orientation of the surface with respect to the body axis, or polarized visual details on the surface itself. To experimentally measure object polarity, Hu, Howard and Palmisano (1999) had observers lying supine on a an elevated bed (Figure 12), look upward into a wide mirror, angled at 45 degrees so they saw a left-right reversed view of the laboratory beyond the head of the bed. If the scene was a blank wall, observers perceived it as a ceiling. However, when intrinsically polarized objects were placed in view, the Figure 12. Mirror bed apparatus of Hu, et al (used with observers perceived their heads permission) as upright, and their bodies tilted by an amount which varied depending on the characteristics of the objects in the scene. The extent of perceived body tilt was used as a measure of visual polarity. Polarized objects placed in the background appeared