Publications
Blackwell, A., Bates, E., & Fisher, D. (1996). The time course of grammaticality judgment. Language and Cognitive Processes, 11(4), 337-406. Abstract. Download PDF version.
Blackwell, A.W. (1995) Artificial Languages/Virtual Brains. Unpublished dissertation. Abstract.
Blackwell, A.W. & Bates, E. (1995). Inducing agrammatic profiles in normals: Evidence for the selective vulnerability of morphology under cognitive resource limitation. Journal of Cognitive Neuroscience, 7, 228-257. Abstract. Download PDF version.
Warren, W.H., Blackwell, A.W., Kurtz, K.J., Hatsopoulous, N.G., & others (1991). On the sufficiency of the velocity field for perception of heading. Biological Cybernetics, 65, 311-320.
Warren, W.H., Mestre, D.R., Blackwell, A.W., & Morris, M.W. (1991). Perception of circular heading from optical flow. Journal of Experimental Psychology: Human Perception and Performance, 17, 28-43.
Warren, W.H., Blackwell, A.W., & Morris, M.W. (1989). Age differences in perceiving the direction of self-motion from optical flow. Journal of Gerontology, 44, 147-153.
Blackwell, Bates, & Fisher, 1996: Abstract
Two experiments investigating the time course of grammaticality judgement are presented. Sentences vary along three dimensions: error type, location of error, and part of speech. Experiment One is a word-by-word "gating" experiment, similar to the gating paradigm of Grosjean (1980). Experiment Two is an "on-line," serial visual presentation of the same sentences to different subjects.
Experiment One shows that for some error types there is considerable inter-subject variability in deciding the error point. Experiment Two shows that there are differences in the speed with which decisions are made for different error types. The significance of these results in relation to the Competition Model of Bates and MacWhinney, and parallel distributed processing models, is discussed.
Blackwell, 1995: Abstract
Various predictions of the Competition Model, a theory of on-line language acquisition and processing (Bates and MacWhinney, 1989) are tested, using the MAL (Miniature Artificial Language) paradigm with both humans and multi-layer neural networks.
Humans were tested in a series of different dialects of an MAL with regular syntactic and morphological rules which could also be used as cues to the meaning of the sentence. The variables manipulated included the frequency of the cue, the reliability of the information it offered, and the surface form of the cue (i.e., word order, agreement morphology, or animacy).
In some conditions, subjects' performance followed the predictions of the Competition Model and profiles seen in child language acquisition, in that their performance initially showed sensitivity to those cues which were more frequent, and then converged later in training upon those cues which were more reliable. However, this effect interacted with the form of the cue in that subjects overall had a more difficult time using agreement morphology than word order, a finding also seen in natural language processing.
Neural networks were tested with languages that were similar in their underlying structure to the MALs used with humans; some versions of the networks showed the same effects as predicted and as seen in normals in that they initially showed sensitivity to those cues which were more frequent, and then converged later in training upon those cues which were more reliable. This effect interacted in an interesting way with the type of network, in that networks with an additional "hidden" layer of processing units were closer to the predicted performance than those with only one layer, even though the one layer networks were well able to solve the problem, suggesting an additional constraint on the types of models that can be used if they are to be psychologically valid.
Implications for the Competition Model and for further research with MALs and their relevance to natural language acquisition are discussed, as well as the useful parallels between MAL research with humans and neural network models.
Blackwell & Bates, 1995: Abstract
The selective vulnerability of morphology in agrammatic aphasia is often interpreted as evidence that closed-class items reside in a particular part of the brain (i.e., Broca's area); thus, damage to a part of the language processor maps onto behavior in a transparent fashion. We propose that the selective vulnerability of grammatical morphemes in receptive processing may be the result of decrements in overall processing capacity, and not the result of a selective lesion.
We demonstrate agrammatic profiles in healthy adults who have their processing capacity diminished by engaging in a secondary task during testing. Our results suggest that this selective profile does not necessarily indicate the existence of a distinct sub-system specialized for the implicated aspects of syntax, but rather may be due to the vulnerability of these forms in the face of global resource diminution, at least in grammaticality judgment.