This paper begins by recapitulating some of the properties and processing principles of the DO model that were presented in the 1990 paper (Kornblum et al.1990), and then expands the number of ensemble in the taxonomy from 4 to 8. It also includes data showing the effects of the number of alternatives in Type 1 and Type 2 ensembles.
Donders was the first to show that RT increases as a function of the number of alternatives (n); that increase is linear when calculated as a function of log n. The data from ten different studies in the literature that used ensembles Types 1 and 2, show that: 1. the slope of that function (RT = log n) changes with different ensembles, and mappings – it is steepest when the mapping is random (i.e. no DO, Type 1), shallowest when the mapping is congruent (S-R DO, Type 2), and in between when the correct response could be identified by rule (DO Type 2). These results are consistent with our model where, depending on the mapping instructions, the response identification process proceeds in one of three ways: 1. the identity rule, 2. a rule other than the identity rule, but a rule nevertheless (which depends on there being DO), and 3.searching through a list. Fitts explained the S-R compatibility effects as the result of information being processed at different levels of efficiency, which is exactly what the automatic, and different identification processes in our model does.
Preliminary results from one of the experiment in Kornblum & Lee (1995) are also presented: with S-R DO (Type 2), there is a 203 ms mapping effect for the relevant stimulus, and a ~50 ms mapping effect for the irrelevant stimulus. When there is no S-R DO (Type 1), there is no effect of mapping at all.