This paper discusses some possibilities and limitations of laboratory research methods for testing theories of second language acquisition. The paper includes a review of 20 experimental lab studies. The review focuses on the motivation for conducting lab studies, the use of artificial or semiartificial language structures, and various design features (including pre- and posttesting, number of subjects, random subject assignment, between- and within-subjects comparisons, treatment materials and procedures). The paper calls for lab studies addressing issues central to SLA theory (“learning” vs. “acquisition”) and ends with some methodological recommendations, concerning the length of experimental treatments, the use of grammaticality judgment tasks, the measurement of reaction times, and the use of retrospective interviews.

This paper illustrates the advantages of laboratory research into SLA by describing two studies of acquisition of second language syntax. The first addresses the question of whether human morphological abilities can be understood in terms of associative processes or whether it is necessary to postulate rule-based symbol processing systems underlying these skills. We demonstrate that acquisition of L2 morphology shows frequency effects for both regular and irregular forms and that the acquisition course of learners' accuracy and reaction time can be accurately simulated by connectionist systems. The second concerns a bootstrapping account of SLA whereby processes of chunking in phonological memory underpin the acquisition of long-term memory for utterances and abstractions of grammatical regularities. It shows that phonological short-term memory is particularly important in the acquisition of long-distance dependencies. In both cases, it is argued that these aspects of SLA reflect associative learning processes. When SLA research is properly focused on acquisition, laboratory research allows investigation of the learners' exposure to evidence, their processes of perception and learning, and their resultant language representations.

A consistent finding in second language acquisition research has been that in the early stages of acquisition learners often receive simplified input. This finding has led researchers to question whether or not simplified input has a facilitative effect on the acquisition process. This study examines the effects of simplified input in early L2 acquisition by experimentally manipulating language input to two groups of learners and then assessing their acquisition longitudinally within a controlled laboratory setting. The impetus for the study described here was Givón's (1990) competition hypothesis that posits that, in early L2 acquisition, vocabulary and grammar compete for memory, attention, and processing capacity. Because one can communicate with vocabulary in absence of grammar but not vice versa, it was proposed that learners receiving pidgin input would acquire vocabulary more efficiently than learners challenged with the dual task of acquiring vocabulary and grammar simultaneously. Furthermore, it was hypothesized that once vocabulary processing skills were automated, learners would acquire grammar more rapidly. Results of a variety of measures reveal that the dual task of acquiring vocabulary and grammar does not hinder either and that the longer the exposure to grammatical input the greater the advantage in real-time grammar processing abilities. Converging evidence from all measures of language learning provides strong support for the usefulness and viability of laboratory study of SLA.

This study is a fine-grained analysis of extensive empirical data on the automatization of explicitly learned rules of morphosyntax in a second language. Sixty-one subjects were taught four morphosyntactic rules and 32 vocabulary items in an artificial language. After they had reached criterion on a set of metalinguistic tests of grammar and vocabulary, they engaged in systematic, computer-controlled comprehension and production practice for 8 weeks. Comprehension practice consisted of choosing between pictures displayed on the computer screen to match a sentence; production practice consisted of typing the correct sentence corresponding to a picture. All subjects were taught the same rules and then practiced them, and all subjects had the same amount of comprehension and production practice, but which rules were practiced in comprehension and which in production varied between groups. Results show that the learning of morphosyntactic rules is highly skill-specific and that these skills develop very gradually over time, following the same power function learning curve as the acquisition of other cognitive skills. These results are consistent with current skill acquisition theory.

This experimental study examines the extent to which 60 adult Japanese ESL learners were able to acquire a rule regulating the argument structure frames of novel verbs of English after exposure to grammatical examples of sentences containing the verbs. Training took place under conditions with no focus on form (implicit and incidental conditions) and with focus on form (enhanced and instructed conditions). The presentation of instances during training was manipulated as a test of predictions made by Logan's (1988, 1990, 1992) memory-based instance theory of automaticity. Results measured in reaction times show similar slopes for automaticity on trained examples in each condition but significant differences in the extent of learning, with the focus on form conditions outperforming the no focus on form conditions in transfer of learned knowledge to accurate judgments of new ungrammatical sentences. Implications are drawn from the results regarding the acquisition of rule-based versus memory-based knowledge from exposure to stimuli in each training condition and the influence of this knowledge on decision-making about grammaticality during the transfer task.

Theories on the role of consciousness and the enhancement of noticing (Schmidt, 1990, 1994; Sharwood Smith, 1993) predict a facilitative effect of explicit knowledge, as built up by explicit instruction, on the acquisition of implicit second language (L2) knowledge. This study investigates the interaction between the presence or absence of explicit instruction and the variables complexity and morphology/syntax in the acquisition of four L2 structures. Two groups of 27 university students, differing in the exposure to explicit instruction, followed a computer-controlled self-study course in an artificial language. Results from computer-controlled posttests confirm the general hypothesis that explicit instruction facilitates the acquisition of L2 grammar. However, no evidence could be reported for the hypotheses predicting a differential effect of explicit instruction depending on the variables complexity and morphology/syntax.

The relation between experimental psychology and second language acquisition research has gone through at least two major swings of the pendulum. During the heyday of behaviorism, the pendulum swung strongly toward psychology. The behaviorist psychologists advised us to think of language learning as nothing more than habit formation (Mowrer, 1960), and second language learning materials reflected an emphasis on repetition, drill, rewards, practice, and conditioning. During the early years of the cognitive revolution, Chomsky (1959) argued that viewing language as a conditioned response (Skinner, 1957) ignores the complexities of both language structure and cognition. Persuaded by these arguments, second language researchers turned away from behaviorist psychology and sought the explanation for language acquisition in universals of language structure (Dulay & Burt, 1974).