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Geoffrey P. Bingham, Mark Mon-Williams, Behnez Jarrahi, Roy Vinner; Cue use under full cue conditions cannot be inferred from use under controlled conditions. Journal of Vision 2005;5(8):405. doi: 10.1167/5.8.405.
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Height-in-the-visual-field (HVF) is the angle between the line of sight and a horizontal when viewing an object. We tested this classic distance cue when it was isolated as information about distance and showed that observers used it reliably to make distance judgments. We then tested the same stimuli with additional information available and observers failed to use the cue at all. This indicates that an inference from cue use in isolated conditions to cue use in full information conditions is not warranted.
Experiment 1: We investigated the use of HVF when it was isolated from other information. Observers (n=8) on a chinrest viewed targets in the dark with one eye. Targets were black square tiles, with phosphorescent texture, arranged to subtend the same visual angle. Observers verbally indicated whether targets lay in one of three frontoparallel planes at near, middle or far distance (N, M, F = 20, 27, 35 cm). Targets were presented randomly 5 times. Three targets were located at the M distance at three eye heights (40, 30, 22.5 cm ) producing 3 gaze angles (34°, 42°, 50° from horizontal). The responses (N, M, F) correlated predictably with gaze angle. Two other targets were placed at the N and F distances along the middle gaze angle (at small and large eye heights, respectively). The distances of these targets did not affect the judgments. HVF reliably determined observers' estimates of location.
Experiment 2: New observers (n=8) did the same experiment but now a phosphorescent checkerboard surface (0.5 m wide × 1 m long) was placed under the targets in dark and lighted conditions. Observers now gauged veridically the distance at which the targets lay independently of HVF. Expts 1 and 2 were repeated using larger eye heights (≈90cm) and distances with identical results.
Conclusions: These results show that inferring how information is used in multi-cue environments from cue use in isolated conditions is not warranted.
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