CUMULATIVE SEMANTIC INHIBITION
Original categories Original categories and Relative position Original categories and Supra-categories Supra-categories
A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 A1 A2 A3 A4 A5 B1 B2 B3 B4 B5
ordinal position within categories 'A' and 'B'
Figure 2. Estimated performance, with standard errors, for the members of two co-categories (A
and B) in different models instantiating different hypothesis. A rationale for choosing among models
is described in the General Discussion.
Leftmost panel: both co-categories are independent; their ordinal positions produce independent
significant effects (N-model 1). Left-center panel: the co-categories depend on one another; the
ordinal position within category and the relative position between categories produce independent
significant effects (N-model 3). Right-center panel: the co-categories depend on one another; both the
ordinal position in the original categories and in the supra-category produce independent significant
effects (N-model 5). Rightmost panel: the co-categories are in fact a single supra-category; only
ordinal position within the supra-category produces a significant effect (model not reported).
approximating test of this hypothesis (dataset size = 215 trials) shows, if anything, the
opposite pattern. The 1st trial of the 2nd co-category is faster than the 5th trial of the 1st
co-category (t(212) = -2.15, p = .033), irrespective of their inter-trial lag (t(212) < 1).
This finding suggests that the effect of relative position of co-categories may be more than
a simple accumulation of inhibition within a supra-category.
Third step: Are co-categories better described as a single encompassing category?
In this third step, we test more formally whether the two co-categories can be func-
tionally reduced to a single supra-category. This account makes a clear prediction. Ordinal
position within the supra-category (range: 1 - 10) should produce a significant effect that
should absorb the effect of ordinal position within the (original) category (range: 1-5).
A representation of the prediction of such a model is plotted on the rightmost panel of
Figure 2. Alternatively, the slowing down of the co-category occurring second may not be
due to the items belonging to a single category. The underlying representation of items that
share a single feature or property within and across co-categories may be responsible for
the effect. An example of such a feature for the co-categories farm and zoo animals could
be four-limbed animal or mammal. This alternative account also makes a clear prediction.
Ordinal position within the supra-category (range: 1 - 10) should produce a significant
effect in addition to the previously reported effect of ordinal position within the (original)
category (range: 1 - 5).
These alternative predictions were tested in N-models 4 and 5 reported in Table 3.
The estimates of N-model 4 show that both the ordinal position within the supra-category
and the ordinal position within the original category have independent significant inhibitory
effects. The effect of supra-category cannot be ascribed to trial position, which was also