Cognitive neuroscience and the English past tense: comments on the paper by Ullman et al

Prosodic Disambiguation of Morphological Ambiguities in Turkish

This study investigates the production and processing of lexical prosody in morphological ambiguities in Turkish. Native speakers of Turkish took part in two read-aloud and two lexical decision experiments. The results showed that in speaking, for both genuine and pseudo words that contrasted in stress, participants changed the fundamental frequency (F0) and intensity to disambiguate; and they changed duration (but not F0 or intensity) to disambiguate words and pseudo-words that did not contrast in stress. In listening, the participants were sensitive to the prosodic (mis)match in stress-contrasting pairs, but not to durational (mis)match presumably because the durational differences between the comparison pairs were shorter than perceivable. The findings show that Turkish speakers use prosody to disambiguate morphologically ambiguous word pairs and that they are sensitive to prosodic cues (at least to those used in stress contrast) when they hear them. Their behavior for pseudo-words suggests that they do so not on the basis of individual word knowledge but productively. The comparison pairs in the current study were segmentally identical, allowing us to attribute the observed prosodic variation only to the morpho-syntactic structure of the ambiguous pairs.

Psycholinguistic measures for German verb pairs: Semantic transparency, semantic relatedness, verb family size, and age of reading acquisition

A central issue in visual and spoken word recognition is the lexical representation of complex words-in particular, whether the lexical representation of complex words depends on semantic transparency: Is a complex verb like understand lexically represented as a whole word or via its base stand, given that its meaning is not transparent from the meanings of its parts? To study this issue, a number of stimulus characteristics are of interest that are not yet available in public databases of German. This article provides semantic association ratings, lexical paraphrases, and vector-based similarity measures for German verbs, measuring (a) the semantic transparency between 1,259 complex verbs and their bases, (b) the semantic relatedness between 1,109 verb pairs with 432 different bases, and (c) the vector-based similarity measures of 846 verb pairs. Additionally, we include the verb regularity of all verbs and two counts of verb family size for 184 base verbs, as well as estimates of age of acquisition and age of reading for 200 verbs. Together with lemma and type frequencies from public lexical databases, all measures can be downloaded along with this article. Statistical analyses indicate that verb family size, morphological complexity, frequency, and verb regularity affect the semantic transparency and relatedness ratings as well as the age of acquisition estimates, indicating that these are relevant variables in psycholinguistic experiments. Although lexical paraphrases, vector-based similarity measures, and semantic association ratings may deliver complementary information, the interrater reliability of the semantic association ratings for each verb pair provides valuable information when selecting stimuli for psycholinguistic experiments.

Towards a computational(ist) neurobiology of language: Correlational, integrated, and explanatory neurolinguistics

We outline what an integrated approach to language research that connects experimental, theoretical, and neurobiological domains of inquiry would look like, and ask to what extent unification is possible across domains. At the center of the program is the idea that computational/representational (CR) theories of language must be used to investigate its neurobiological (NB) foundations. We consider different ways in which CR and NB might be connected. These are (1) A Correlational way, in which NB computation is correlated with the CR theory; (2) An Integrated way, in which NB data provide crucial evidence for choosing among CR theories; and (3) an Explanatory way, in which properties of NB explain why a CR theory is the way it is. We examine various questions concerning the prospects for Explanatory connections in particular, including to what extent it makes sense to say that NB could be specialized for particular computations.

A behavioral study of regularity, irregularity and rules in the English past tense

Opposing views of storage and processing of morphologically complex words (e.g., past tense) have been suggested: the dual system, whereby regular forms are not in the lexicon but are generated by rule, while irregular forms are explicitly represented; the single system, whereby regular and irregular forms are computed by a single system, using associative connections; and a system whereby phonological rules relate both regular and irregular past to present tense forms. Two reaction time experiments investigated the production of the past tense in English in response to the auditory presentation of the present tense of the verb. The first experiment addressed the methodology of presenting regulars and irregulars in blocked form as in a previous study (Jaeger et al. in Language 72:451-497, 1996). Blocked presentation results showed longer RTs for the elicitation of irregular pasts than for regular pasts; however, there were no differences between regular and irregular elicitation when the presentation was randomized, indicating that it is rules that are being primed. The second experiment tested whether the response time advantage found for blocked regular verbs in the first experiment might also extend to irregular verb forms exhibiting the same sub-regularity (e.g., sing-sang may prime ring-rang). Results showed a trend towards slower RTs when past tense forms from different sub-regularities follow one another, suggesting interference between one sub-regularity and another.

Electrophysiological evidence for the continuous processing of linguistic categories of regular and irregular verb inflection in German

A central question concerning word recognition is whether linguistic categories are processed in continuous or categorical ways, in particular, whether regular and irregular inflection is stored and processed by the same or by distinct systems. Here, we contribute to this issue by contrasting regular (regular stem, regular suffix) with semi-irregular (regular stem, irregular suffix) and irregular (irregular stem, irregular suffix) participle formation in a visual priming experiment on German verb inflection. We measured ERPs and RTs and manipulated the inflectional and meaning relatedness between primes and targets. Inflected verb targets (e.g., leite, "head") were preceded either by themselves, by their participle (geleitet, "headed"), by a semantically related verb in the same inflection as the target (führe, "guide") or in the participle form (geführt, "guided"), or by an unrelated verb in the same inflection (nenne, "name"). Results showed that behavioral and ERP priming effects were gradually affected by verb regularity. Regular participles produced a widely distributed frontal and parietal effect, irregular participles produced a small left parietal effect, and semi-irregular participles yielded an effect in-between these two in terms of amplitude and topography. The behavioral and ERP effects further showed that the priming because of participles differs from that because of semantic associates for all verb types. These findings argue for a single processing system that generates participle priming effects for regular, semi-irregular, and irregular verb inflection. Together, the findings provide evidence that the linguistic categories of verb inflection are processed continuously. We present a single-system model that can adequately account for such graded effects.

Evidence for early morphological decomposition in visual word recognition

We employ a single-trial correlational MEG analysis technique to investigate early processing in the visual recognition of morphologically complex words. Three classes of affixed words were presented in a lexical decision task: free stems (e.g., taxable), bound roots (e.g., tolerable), and unique root words (e.g., vulnerable, the root of which does not appear elsewhere). Analysis was focused on brain responses within 100-200 msec poststimulus onset in the previously identified letter string and visual word-form areas. MEG data were analyzed using cortically constrained minimum-norm estimation. Correlations were computed between activity at functionally defined ROIs and continuous measures of the words' morphological properties. ROIs were identified across subjects on a reference brain and then morphed back onto each individual subject's brain (n = 9). We find evidence of decomposition for both free stems and bound roots at the M170 stage in processing. The M170 response is shown to be sensitive to morphological properties such as affix frequency and the conditional probability of encountering each word given its stem. These morphological properties are contrasted with orthographic form features (letter string frequency, transition probability from one string to the next), which exert effects on earlier stages in processing ( approximately 130 msec). We find that effects of decomposition at the M170 can, in fact, be attributed to morphological properties of complex words, rather than to purely orthographic and form-related properties. Our data support a model of word recognition in which decomposition is attempted, and possibly utilized, for complex words containing bound roots as well as free word-stems.