Contour deletion as a method for identifying the weights of features underlying object recognition

A prerequisite for comparative work on object recognition is a method for identifying the features actually extracted from the form. The method introduced here with pigeons is discrimination training between two simple line drawings, followed by a generalization test in which contour is deleted from the reinforced drawing. In Condition 1, the line drawings were a square (S+) versus a triangle (S-); for Condition 2, the line drawings were planar projections of a cube (S+) versus a truncated pyramid (S-). The generalization decrement between responses to S+ and responses to test stimuli provides a quantitative index of the weight assigned to each feature. Contour deletion at either vertices or midsegments produced a decrement in the rate of responding, showing that each contour was represented as a feature. The generalization decrement to forms containing vertices with midsegments deleted was larger than the generalization decrement to forms containing midsegments with vertices deleted. Therefore, it appears that midsegments are weighted more strongly as features than vertices. Contour deletion provides a direct method for identifying the visual features underlying object recognition and lays a foundation for the development of comparative theories of object recognition.     

Proper methodologies for psychological and sociological studies conducted via the Internet

This paper outlines specific methodologies for conducting research via computer networks. We discuss advantages of Internet experimentation over previous modes of telecommunication-facilitated research and characterize features of studies that can benefit from Internet access and those which are unlikely to. We point out pitfalls and suggest a range of potential solutions in terms of specific practical techniques for managing the design, dissemination, and collection of Internet materials. We also discuss techniques for minimizing attrition and for adapting to recalcitrance presented by “hacker” vandalism.