Mechanisms responsible for cue-competition effects

The mechanisms responsible for cue competition were investigated. In Chapter 1, an overview of the literature that led to and originated from the discovery of cue competition effects (Kamin, 1969 Wagner, Logan, Haberlandt & Price, 1968) attested the diversity of theoretical accounts available to explain these phenomena. The subsequent empirical chapters focused on the predictions made by two rather distinct classes of theory: the Comparator Hypothesis (Miller & Matzel, 1988 Denniston, Savastano & Miller, 2001) and the attentional theory of Mackintosh (1975). Throughout the thesis, their predictions were contrasted to those derived from Standard Associative Theory e.g. Rescorla- Wagner(1972) model . The experiments contained in Chapters 2 and 3 used a Pavlovian appetitive procedure with rats to examine a number of predictions made by the Comparator Hypothesis. In Chapter 2, Experiment 1 tested the prediction that a conditioned inhibitor should have no influence on the excitatory status of the CS in which presence it is trained. Experiment 2 examined whether single-phase blocking disappears with asymptotic training. Further analysis of the Comparator Hypothesis was provided in the two experiments contained in Chapter 3. Experiments 3 and 4 assessed the prediction that adding a stimulus to a continuously trained CS should deteriorate conditioned responding to the latter. The experiments in Chapters 4 and 5, which used an autoshaping procedure in pigeons, were concerned with the attentional theory of Mackintosh (1975). In Chapter 4, Experiments 5 and 6 tested a novel behavioural technique intended to measure associability changes. Evidence of associability changes was found when visual patterns, but not colours, were compared. Experiment 7 explored the locus central or peripheral of the mechanism responsible for these changes. Drawing from the results in Chapter 4, Experiment 8 (Chapter 5) examined whether associability changes can provide a complete account of the relative validity effect in pigeons. Overall, the results challenge the accounts of cue competition advanced by both the Comparator Hypothesis (Miller & Matzel, 1988, Denniston et al., 2001) and the attentional theory of Mackintosh (1975). Without necessarily validating it, the results are mostly compatible with the analysis provided by the Rescorla-Wagner (1972) model