Can amnesic patients learn without awareness? New evidence comparing deterministic and probabilistic sequence learning

Can associative learning take place without awareness? We explore this issue in a sequence learning paradigm with amnesic and control participants, who were simply asked to react to one of four possible stimuli on each trial. Unknown to them, successive stimuli occurred in a sequence. We manipulated the extent to which stimuli followed the sequence in a deterministic manner (noiseless condition) or only probabilistically so (noisy condition). Through this paradigm, we aimed at addressing two central issues: first, we asked whether sequence learning takes place in either
condition with amnesic patients. Second, we asked whether this learning takes place without awareness. To answer this second question, participants were asked to perform a subsequent sequence generation task under inclusion and exclusion conditions, as well as a recognition task. Reaction times results showthat amnesic patients learned the sequence only in the deterministic condition. However, they failed to be able to reproduce the sequence in the generation task. In contrast, we found learning for both sequence structures in control participants, but only control participants exposed to a deterministic sequence were successful in performing the generation task, thus suggesting that the acquired knowledge can be used consciously
in this condition. Neither amnesic nor control participants showed correct old/new judgments in the recognition task. The results strengthen the claim that implicit learning is at least partly spared in amnesia, and the role of contextual information available for learning is discussed.
© 2006 Elsevier Ltd. All rights reserved.
Keywords: Amnesia; Sequence learning; Awareness
1. Introduction
Whether associative learning can take place without awareness
is a central issue for the cognitive neurosciences. Amnesic
patients, whose explicit memory is severely impaired, provide
us with a unique opportunity to explore this issue. In this paper,
we explored the extent to which such patients are able to learn
about the regularities contained in deterministic or probabilistic
sequences of events presented visually in the context of a
choice reaction time task – a robust paradigm known as sequence
learning, and in which incidental learning has been abundantly
documented, both with normal participants (Nissen&Bullemer,
1987; Cleeremans&McClelland, 1991; Reed&Johnson, 1994)
as well as with special populations (Nissen & Bullemer, 1987;
Muriel Vandenberghe, Nicolas Schmidt, Patrick Fery, Axel Cleeremans
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