The dual-task SRT procedure: fine-tuning the timing.

In the standard sequential reaction time study, subjects are presented with a repeating sequence of targets to which they must respond as rapidly as possible. With practice reaction times decrease, suggesting a learned ability to exploit the repeating patterns in the display. In a common variation, a second task is interposed, typically a tone-counting task in which subjects must keep track of the frequency with which particular tones occur. In the canonical experiment, these tones appear at varying times in the interval between the subjects' response to a target and the next target. Data are presented that show that this latter variable (the RSOA, response-secondary stimulus onset asynchrony) actually plays an important but previously hidden role in these experiments. A model based on an extension of the notion of the psychological refractory period is introduced to explain these findings.

The assessment of cognitive procedural learning in amnesia: why the tower of Hanoi has fallen down.

The Tower of Hanoi has been widely accepted as an evaluation of cognitive procedural learning in amnesia but inconsistent findings have raised questions about the nature of the learning process involved in this task. This article presents the performance of a hippocampal amnesic, MS, who, showing poor learning across daily sessions of a formal evaluation, subsequently solved the puzzle through spontaneous use of a declarative-level strategy (the odd-even rule), suggesting that his primary approach to the task was the deployment of declarative solution-searching strategies. The presented data suggest normal learning within daily sessions, but subnormal learning across daily sessions due to the forgetting of acquired declarative information. It is suggested that tasks that are potentially solvable by an algorithm or rule, as is the Tower of Hanoi, be regarded as inappropriate for use in cognitive procedural assessments.

Another wrinkle on the dual-task SRT experiment: it's probably not dual task.

In the standard serial reaction time (SRT) experiment, subjects are required to respond rapidly to a structured sequence of visual targets. Evidence that subjects have acquired knowledge of the structure is obtained by modifying the structured nature of the sequence and noting whether reaction times increase. In the dual-task SRT experiment, a "secondary" tone-counting task is introduced, and the extent to which learning of the "primary" target sequence is compromised is noted. Here we present data that strongly imply that while the psychologists who designed this "dual-task" experiment may have viewed it this way, this may not be the best way to characterize it. The suggestion is that this "duality" is illusory and that we should probably be treating the tone-counting task as a potential source of additional patterns of covariation in a complex, multicomponent display and not as a "secondary," attention-diverting factor.

Implicit and explicit learning: differential effects of affective states.

Two experiments using a standard artificial grammar paradigm were conducted to examine the role of affective states, specifically anxiety and depression, on implicit learning. The main purpose was to broaden the range of human functioning explored through the application of the robustness principle in the evolutionary framework recently developed by Reber which predicts that cognitive processes which rely upon unconscious, implicit processes should be less affected by affective states than those which rely upon conscious, explicit processes. In Study 1 (N = 60), high test anxiety was associated with performance deficits in the explicit components of the task; no differences were found in the implicit phases of the task. In Study 2 (N = 160), varying levels of subclinical depression were unrelated to both implicit and explicit functioning. The contrasting findings of the two studies are discussed in terms of the differential cognitive effects and adaptive implications of these two affective states.

Implicit and explicit learning: individual differences and IQ.

We explored the degree to which individual differences in performance were observed in a group of subjects who worked with two different tasks: one implicit and one explicit. The implicit task was a standard artificial grammar-learning task; the explicit was a series-completion problem-solving task. Substantial individual differences were found between subjects on the explicit task; relatively small individual differences were found on the implicit task. Moreover, performance on the explicit task correlated strongly with intelligence quotient, but performance on the implicit task did not. Data from previous experiments were also found to be in agreement with these results. The findings are presented in the context of a general theory of implicit learning proposed recently by Reber (1989a, in press) that derives from considerations of the evolution of cognitive processes. This evolutionary model argues that unconscious, implicit induction systems are evolutionarily older and antedate conscious, explicit learning processes, and that this antiquity carries with it particular patterns of function that differentiate implicit processes from explicit processes.

More thoughts on the unconscious: reply to Brody and to Lewicki and Hill.

Brody (1989) and Lewicki and Hill (1989) present commentaries on my central thesis (Reber, 1989) that there exist powerful induction routines that operate largely independently of awareness and yield rich and complex tacit knowledge that resists attempts to make it conscious, although these commentaries are of dramatically different kinds. Because there is a fairly clear basis of agreement between Lewicki and Hill and the points that I made, this reply deals almost entirely with the issues raised by Brody. The focus is on two classes of issues: (a) those of a methodological nature that surround the general problem of doing experiments on unconscious cognition and (b) those that derive from considerations of evolutionary biology that provide a basis for arguing that implicit operations are primary and form the foundation for conscious processes.

Implicit learning: robustness in the face of psychiatric disorders.

The performance of a group of psychiatric inpatients on two different cognitive tasks was compared with that of a control group of college undergraduates. The task in the first experiment was implicit learning of a complex, synthetic grammar; the task in the second experiment was explicit learning of relatively simple letter-to-number matching rules. In the first experiment, differences between the normals and the psychiatrically impaired were found on the preliminary memorization task but not on the implicit grammar learning task; in the second experiment, differences were observed on all phases of the experiment, with the inpatients performing no better than chance. These findings provide support for the hypothesis that, under appropriate conditions, individuals suffering from serious disorders may show no deficits when working with complex and abstract stimulus domains while showing serious performance problems when working with relatively simple, concrete stimuli. The key factor is that the former were presented as tasks that tap nonreflective, implicit processes, whereas the latter were put forward as ones that recruit conscious, explicit processes.

On psycho-linguistic paradigms.

Some frustration and confusion are detectable in the work of those researching the psychology of language. The suggestion is made that the lack of focus is due, in part, to the lack of a dominant paradigm or overall system within which to view recent developments. It appears possible to isolate three broad and conflicting perspectives within the contemporary Zeitgeist: an Association position with behaviorist traditions, a Process approach with origins in general cognitive theory, and a Content approach which has evolved along with the resurgence of a nativist position in linguistic theory. Several issues-empirical, theoretical, and philosophical-are discussed, each within the context of the three potential paradigms. Although no effort has been made to be prescriptive, it would appear that the Process orientation provides the most radical alternative, and it is implicit throughout the paper that the Zeitgeist is moving in this direction.