Test of an integrated associative theory of timing

点击翻译按钮获取中文摘要

Understanding learning is a central issue in psychology, and has been extensively studied, especially in animal subjects. The theory of associative learning asserts that the mental representations of co-occurring events become linked, such that presentation of one can elicit the thought of the other. This is probably the most elaborated theory of learning in the field, and has considerable explanatory power. For example, the rules governing the conditions under which associations may be formed explains the sensitivity of animals to correlations between environmental events, and hence their ability to learn selectively about events that are causally related, rather than those that co-occur by chance. However, there are some phenomena that are at present outside the scope of associative learning models. For example, in a standard associative learning task an event, which is usually of fixed duration, is followed by an outcome, and the animal will learn not only that the event will be followed by the outcome (conditioning) but when - an effect called timing. Yet despite the intimate relation between these two types of learning, theories of conditioning and of timing have developed independently. Given the fact that timing and conditioning arise alongside each other in the same learning tasks, one might argue that this theoretical framework is fundamentally misconceived, and in more recent years information processing theories of timing have been developed that seek to account for both phenomena. This approach is parsimonious in theory - but in practice, the ability of these such theories to explain conditioning is limited, and much of the explanatory power of associative theory is lost. The alternative approach, to explain timing within the framework of conditioning theory, has been relatively neglected. This proposal aims to test a version of associative theory that has been specifically developed to explain timing effects, with the ultimate objective of developing a unified associative account of conditioning and timing. The predictions of the modified associative theory will be compared with those of an information processing account that has been adapted to explain conditioning. This will be achieved in part by examining the effects of temporal manipulations on a series of associative learning tasks. We will also use lesion techniques. The associative theory we have adapted to explain timing also provides an explanation of some of the impairments in cognition produced by damage to the hippocampus, and applying it results in some specific predictions about the conditions under which timing and related deficits will be found in hippocampal animals. Another set of experiments will test these predictions as a means of evaluating our version of this associative theory. This work has implications at a number of levels. Theoretically, by evaluating the modified associative theory, we will assess the extent to which an associative account of timing effects is feasible. Practically, the work on timing has significant clinical implications, insofar as timing abnormalities are heavily implicated in attention-deficit hyperactivity disorder (ADHD), as well as in schizophrenia and depression. As the work described in this proposal aims at a complete understanding of the nature of timing, this will aid interpretation of such abnormalities, and so directly inform attempts to identify their neural basis. In addition the section looking at hippocampal function will increase our understanding of the psychological role of this structure, which is heavily implicated in mediating conditions such as Alzheimer's disease. Thus our work will have therapeutic implications in a number of areas. Finally, the study of learning in artificial agents uses models very similar to those used in psychology. The data generated by the experiments we propose should thus be of use in helping to develop theories of machine learning.