Arthur S. Reber

Implicit learning of artificial grammars

Two experiments were carried out to investigate the process by which Ss respond to the statistical nature of the stimulus array, a process defined as “implicit learning”. An artificial grammar was used to generate the stimuli. Experiment I showed that Ss learned to become increasingly sensitive to the grammatical structure of the stimuli, but little was revealed about the nature of such learning. Experiment II showed that information gathered about the grammar in a memorization task could be extended to a recognition task with new stimuli. Various analyses of the data strongly implied that Ss were learning to respond to the general grammatical nature of the stimuli, rather than learning to respond according to specific coding systems imposed upon the stimuli. It was argued that this “implicit” learning is similar in nature to the “differentiation” process of perceptual learning espoused by Gibson and Gibson (1955) .

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.

Analogic and abstraction strategies in synthetic grammar learning: A functionalist interpretation

Abstract Subjects learned artificial grammars under two conditions of acquisition: paired-associate learning and observation of exemplars. The former procedure was strongly associated with the establishment of a fairly concrete memorial space consisting of specific items and parts of items and the use of an analogic strategy for making decisions about novel stimuli. The observation procedure was strongly associated with the induction of an abstract representation of the rules of the grammar and the use of a correspondence strategy for decision making. Moreover, this latter procedure led to more robust knowledge and better overall performance. Analyses of both objective response patterns and subjective introspections yielded coordinated data in support of this distinction. The relationships between acquisition condition and cognitive strategy are discussed from a functionalist point of view.

The cognitive unconscious: An evolutionary perspective

Abstract In recent decades it has become increasingly clear that a substantial amount of cognitive work goes on independent of consciousness. The research has been carried out largely under two rubrics, implicit learning and implicit memory. The former has been concerned primarily with the acquisition of knowledge independent of awareness and the latter with the manner in which memories not readily available to conscious recall or recognition play a role in behavior; collectively these operations comprise the essential functions of the cognitive unconscious. This paper reviews the recent history of work on these issues, identifies some of the problems confronting researchers, and introduces a theoretical framework based on principles of evolutionary biology within which to view them. The argument is that the cognitive unconscious, despite its apparent sophistication, is of considerable evolutionary antiquity and antedates conscious cognitive systems by a considerable amount of time. Various entailments of this evolutionary perspective are explored including such issues as phylogeny and ontogeny of implicit processes, the robustness of the implicit functions as displayed by the capacity to resist disruptions from psychological and neurological disorders, the relationship between implicit cognition and intelligence, and individual differences in implicit cognitive abilities.

Implicit learning: An analysis of the form and structure of a body of tacit knowledge.

Abstract Subjects learned implicitly the underlying structure of an artificial language by memorizing a set of representative exemplars from the language. The form and structure of their resulting knowledge of the language was evaluated and analyzed over a four day period by several procedures: (a) solving anagrams from the language, (b) determining the well-formedness of novel letter strings, and (c) providing detailed introspective reports. Several important implications about implicit acquisition of a novel complex system emerged. First, the memorial representation of a structured system is acquired through the dual operations of a differentiation-like process based upon relational invariances and a configurational process based upon overall structure. Second, the form of tacit knowledge is an abstract representation of the intrinsic structure of the stimulus field. Third, while the ability to make explicit what is known implicitly increases with performance levels, the conscious apprehension of structure always lags behind what is known unconsciously.

An evolutionary context for the cognitive unconscious

Abstract This paper is an attempt to put the work of the past several decades on the problems of implicit learning and unconscious cognition into an evolutionary context. Implicit learning is an inductive process whereby knowledge of a complex environment is acquired and used largely independently of awareness of either the process of acquisition or the nature of that which has been learned. Characterized this way, implicit learning theory can be viewed as an attempt to come to grips with the classic epistemological issues of knowledge acquisition, representation and use. The argument is made that the process, despite its seeming cognitive sophistication, is of considerable evolutionary antiquity and that it antedates awareness and the capacity for conscious control of mentation. Various classic heuristics from evolutionary biology are used to substantiate this claim and several specific entailments of this line of argument are outlined.

Very long term memory for tacit knowledge

Abstract Very long term memory for abstract materials was examined by recalling subjects who had served in a synthetic grammar learning experiment two years earlier. In that study (Reber & Allen, 1978) we differentiated among several cognitive modes of acquisition, their resultant memorial representations, and their associated decision processes. Two years later and without any opportunity for rehearsal or relearning, subjects still retain knowledge of these grammars to a remarkable degree. Although some differences have become blurred with the passage of time, the form and structure of that knowledge and the manner in which it is put to use remain strikingly similar to the original. That is, differences traceable to acquisition mode and conditions of initial training can still be observed. As in the original study, these results are discussed within the general context of a functionalist approach to complex cognitive 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.

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.

The locus of focus: The effect of switching from a preferred to a non-preferred focus of attention

Abstract Focusing strategies are known to play a significant role in motor performance, with individuals who use an internal focus on body movement typically showing poorer outcomes than those who focus on features of the external environment. Focus of attention and switching of ones focus are examined in the context of two different complex motor skills along with a factor not previously examined systematically, individual preference. In both experiments, participants were introduced to focusing strategies that might be employed when attempting a sensorimotor task. Explanations of both strategies were given to participants. Specifically, for an internal focus, participants were instructed to concentrate on their body movements, while for an external focus, they were instructed to focus on aspects in the environment. They were then asked which strategy they preferred. Participants then continued either with their preferred focus or were instructed to switch to their non-preferred focus. The advantage that the external focus typically enjoys turns out not to be a simple one and interacts with individual preference and with the “forced-opposite” manipulation. Our results support the growing consensus that encouraging individuals to adopt an internal focusing strategy is counterproductive in complex sensorimotor tasks. They also suggest that individual preferences play a role.