AUTHOR=Bimler David , Izmailov Chingis , Paramei Galina 

TITLE=Processing bimodal stimuli: integrality/separability of color and orientation

JOURNAL=Frontiers in Psychology

VOLUME=Volume 4 - 2013

YEAR=2013

URL=https://www.frontiersin.org/journals/psychology/articles/10.3389/fpsyg.2013.00759

DOI=10.3389/fpsyg.2013.00759

ISSN=1664-1078

ABSTRACT=We examined how two distinct stimulus features, orientation and colour, interact as contributions to global stimulus dissimilarity. Five subjects rated dissimilarity between pairs of bars (N = 30) varying in colour (four cardinal hues, plus white) and orientation (six angles at 30° intervals). An exploratory analysis with individual-differences multidimensional scaling resulted in a 5D solution, with two dimensions required to accommodate the circular sequence of the angular attribute, and red-green, blue-yellow and achromatic axes for the colour attribute. Weights of the orientation subspace relative to the colour subspace varied among the subjects, from a 0.32:0.61 ratio to 0.53:0.44, emphasis shifting between colour and orientation. In addition to Euclidean metric, we modelled the interaction of colour and orientation using Minkowski power metrics across a range of Minkowski exponents p, including the city-block (p = 1), Euclidean (p = 2) and Dominance metric (p à ¥) as special cases. For averaged data, p ~ 1.3 provided the best fit, i.e. intermediate between separable and integral features. For individual subjects, however, the metric exponent varied significantly from p = 0.7 to p = 3.1, indicating a subject-specific rule for combining colour and orientation, as in Tversky and Gati’s variable-weights model. No relationship was apparent between dimensional weights and individual p exponents. Factors affecting dimensional integrality are discussed, including possible underlying neural mechanisms where the interaction of the low-level vision attributes orientation and colour might shift between uncorrelated (p =1) or correlated (p ³ 2) forms.