Axis of elongation can determine reference frames for object perception

Object perception remains constant in the face of much retina image variability. One way to achieve such constancy is to represent objects with respect to a reference frame, and many theories of object recognition assume that, among other factors, observers use objects' primary axes of elongation to derive reference frames. However, the limited research directly addressing this assumption suggests that the role of axis of elongation may not be as central as previously thought (Palmer, 1990; Quinlan & Humphreys, 1993). The present study reexamines elongation's role in determining reference frames, adapting Palmer's paradigm to determine the extent to which surrounds bias the perception of ambiguously oriented objects: equilateral triangles. When surrounds were oriented inconsistently with experimentally constrained correct responses, response times increased with surrounds' elongation. These results hold for both symmetric and asymmetric surrounds, suggesting that elongation alone is sufficient to construct a reference frame for object perception.