  Research on interference has provided evidence that the formation of
dependencies between non-adjacent words relies on a cue-based retrieval
mechanism. Two different models can account for one of the main predictions of
interference, i.e., a slowdown at a retrieval site, when several items share a
feature associated with a retrieval cue: Lewis and Vasishth's (2005)
activation-based model and McElree's (2000) direct access model. Even though
these two models have been used almost interchangeably, they are based on
different assumptions and predict differences in the relationship between
reading times and response accuracy. The activation-based model follows the
assumptions of ACT-R, and its retrieval process behaves as a lognormal race
between accumulators of evidence with a single variance. Under this model,
accuracy of the retrieval is determined by the winner of the race and retrieval
time by its rate of accumulation. In contrast, the direct access model assumes
a model of memory where only the probability of retrieval varies between items;
in this model, differences in latencies are a by-product of the possibility and
repairing incorrect retrievals. We implemented both models in a Bayesian
hierarchical framework in order to evaluate them and compare them. We show that
some aspects of the data are better fit under the direct access model than
under the activation-based model. We suggest that this finding does not rule
out the possibility that retrieval may be behaving as a race model with
assumptions that follow less closely the ones from the ACT-R framework. We show
that by introducing a modification of the activation model, i.e, by assuming
that the accumulation of evidence for retrieval of incorrect items is not only
slower but noisier (i.e., different variances for the correct and incorrect
items), the model can provide a fit as good as the one of the direct access
model.
