Some researchers have argued that the category learning literature is conclusive: people
learn to generalise from past experiences to novel ones using multiple learning systems
(Ashby & Maddox, 2011). To the extent that this claim is true, it is due in no small part
to work investigating the predictions of the dual-system model COVIS (COmpetition between
Verbal and Implicit Systems; Ashby, Alfonso-Reese, Turken, & Waldron, 1998).
The work presented here investigates the evidence for this model.
In Chapter 1, I describe the main features of the COVIS model and briefly review some
of the evidence that supports this model. This section highlights two main problems
with this literature. First, that many of the studies that have purported to support a dualsystems
description of category learning have been found to be flawed when re-examined
by independent researchers. This observation is explored more deeply in the next two
chapters, where I attempted to reproduce the work of two studies argued to support the
COVIS literature. In Chapter 2, I re-examined the work reported by Ashby, Maddox, and
Bohil (2002) that looked at the effect of training type on category learning. In Chapter 3,
I re-examined work reported by Spiering and Ashby (2008) that looked at the effect of
training order on category learning. Both these chapters failed to find evidence for two
systems of category learning.
The second issue raised in Chapter 1 is that none of the studies cited in support of COVIS
critically examined the fundamental assumptions of the model. More specifically, Chapters
4 and 5 looked at how participants complete the categorisation tasks used in this
literature. In Chapter 4, I conducted experimental work to determine whether some category
structures are learned implicitly, as argued throughout the COVIS literature. Then,
in Chapter 5 I conducted several simulations to investigate an analysis used ubiquitously
in the COVIS literature to determine the strategies participants use to complete categorisation
tasks. This analysis is a critical manipulation check for all these experiments.
However, I found evidence that the analysis systematically over-estimates the evidence
for dual-systems. Furthermore, both these chapters found evidence to suggest that the
evidence for the COVIS model can be explained without needing to assume that participants
can learn implicitly.
Finally, in Chapter 6 I bring these threads together to discuss the implications for the
COVIS model.
Date of Award | 2017 |
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Original language | English |
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Awarding Institution | |
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Supervisor | Andy Wills (Other Supervisor) |
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Critique of a dual-system model of category learning
Edmunds, C. E. R. (Author). 2017
Student thesis: PhD