Author's School

Graduate School of Arts & Sciences

Author's Department/Program



English (en)

Date of Award

Summer 9-1-2014

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Ian G Dobbins


A variety of factors influence how we make decisions about our own memories. When judging a person on the street as novel or familiar, one appeals to an internal cutoff value known as a decision criterion; if an individual is less familiar than this criterion value, he is judged as new, and vice versa. A host of research has demonstrated that people can explicitly and judiciously update their decision criteria based on a variety of factors such as the prevalence of old and new items, rewards and punishments, and simple instructions. One oft overlooked variable that affects criterion placement and movement is the type and history of feedback an individual has received. Feedback can sometimes produce robust changes in recognition decision-making without an individual's awareness of the changes in his own behavior. This dissertation proposes that this sort of influence on criterion placement represents an implicit learning process; akin to well-established implicit learning processes such as artificial grammar learning or implicit categorization learning (e.g., the weather prediction task).

Three experiments were conducted relating common findings from the implicit learning literature to feedback-based criterion learning. The experiments used a biased feedback procedure designed to produce robust criterion shifts by differentially reinforcing one class of recognition error (e.g., 70% of false alarms are falsely broadcast as "correct."). In other words, the paradigm uses false positive feedback to influence the recognition criterion, producing robust criterion shifts that do not appear apparent to the observer.

The first experiment examined whether observers can volitionally inhibit the influence of false positive feedback. If this learning is relatively unconscious, observers should not be able to ignore feedback designed to influence their responding. Participants were instructed to either "use the feedback to improve their performance" or to "ignore the feedback and not let it inhibit [their] performance." This experiment demonstrated that observers are unable to inhibit the effects of false positive feedback on their responding. In other words, despite instructions otherwise, participants told to ignore the feedback were seemingly unable to do so.

The second experiment examined whether a decision criterion reinforced for one class of stimuli (words) would transfer to a separate class of stimuli with completely different surface features (faces). Many classes of implicit learning tend to produce knowledge that is fairly abstract and not tied to the surface features of items; if this criterion learning mechanism behaves similarly, one would expect criterion to transfer to faces despite never receiving reinforcement. Participants were tested on lists of words and faces; they received biased feedback following words, but never received feedback following faces. Nonetheless, participants showed robust criterion shifts to both words and faces, suggesting that what is learned appears to be fairly abstract (in that it is not tied to the surface features of the item).

Finally, the third experiment examined whether what is learned is environmentally- or motor-dependent by adjusting the test context after learning. Many implicit learning phenomena are tied to the type of motor response given or the environmental context in which they were learned; if this criterion learning mechanism behaves similarly, one would expect criterion learning to be disrupted if participants were transferred to a new testing context. Participants received biased feedback across several computer-based tests, and were then transferred to a new context (with a paper and pencil memory test) or retained in the same context for a final (computer-based) test. Surprisingly, participants who were tested in a new context still showed criterion learning in this new testing context. These findings converge with Experiment 2 to suggest the learning is yet more abstract in that it is not tied to a given motor response or environmental context. These findings are all consistent with the implicit learning literature, suggesting that implicit learning mechanisms in fact govern how we make decisions about our own explicit memories.



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