Elaboration over a Discourse Facilitates Retrieval in Sentence Processing.

Language comprehension requires access to stored knowledge and the ability to combine knowledge in new, meaningful ways. Previous work has shown that processing linguistically more complex expressions ('Texas cattle rancher' vs. 'rancher') leads to slow-downs in reading during initial processing, possibly reflecting effort in combining information. Conversely, when this information must subsequently be retrieved (as in filler-gap constructions), processing is facilitated for more complex expressions, possibly because more semantic cues are available during retrieval. To follow up on this hypothesis, we tested whether information distributed across a short discourse can similarly provide effective cues for retrieval. Participants read texts introducing two referents (e.g., two senators), one of whom was described in greater detail than the other (e.g., 'The Democrat had voted for one of the senators, and the Republican had voted for the other, a man from Ohio who was running for president'). The final sentence (e.g., 'The senator who the {Republican/Democrat}had voted for…') contained a relative clause picking out either the Many-Cue referent (with 'Republican') or the One-Cue referent (with 'Democrat'). We predicted facilitated retrieval (faster reading times) for the Many-Cue condition at the verb region ('had voted for'), where readers could understand that 'The senator' is the object of the verb. As predicted, this pattern was observed at the retrieval region and continued throughout the rest of the sentence. Participants also completed the Author/Magazine Recognition Tests (ART/MRT; Stanovich and West, 1989), providing a proxy for world knowledge. Since higher ART/MRT scores may index (a) greater experience accessing relevant knowledge and/or (b) richer/more highly structured representations in semantic memory, we predicted it would be positively associated with effects of elaboration on retrieval. We did not observe the predicted interaction between ART/MRT scores and Cue condition at the retrieval region, though ART/MRT interacted with Cue condition in other locations in the sentence. In sum, we found that providing more elaborative information over the course of a text can facilitate retrieval for referents, consistent with a framework in which referential elaboration over a discourse and not just local linguistic information directly impacts information retrieval during sentence processing

Event-related potentials elicited by spoken relative clauses

Sentence-length event-related potential (ERP) waveforms were obtained from 23 scalp sites as 24 subjects listened to normally spoken sentences of various syntactic structures. The critical materials consisted of 36 sentences each containing one of 2 types of relative clauses that differ in processing difficulty, namely Subject Object (SO) and Subject Subject (SS) relative clauses. Sentence-length ERPs showed several differences in the slow scalp potentials elicited by SO and SS sentences that were similar in their temporal dynamics to those elicited by the same stimuli in a word-by-word reading experiment, although the effects in the two modalities have non identical distributions. Just as for written sentences, there was a large, fronto-central negativity beginning at the linguistically defined "gap" in the SO sentences; this effect was largest for listeners with above-median comprehension rates, and is hypothesized to index changes in on-line processing demands during comprehension

Forest fires, woodland caribou and land use policies in northwestern Ontario (Rangifer tarandus)

Woodland caribou (Rangifer tarandus caribou) are a threatened species in Ontario\u27s boreal forest. Caribou require habitat that supports appropriate forage, including large areas of lichen rich forests. This research examines two dynamics that influence woodland caribou habitat in northwestern Ontario. These dynamics are forest fires and land use policies. The effects of forest fires are assessed quantitatively at both the ecosite and landscape scales within Woodland Caribou Provincial Park. Land use policy and management activities are evaluated using a case study and a policy analysis of protected area and forest management approaches to woodland caribou conservation in this region. Forest fires in Woodland Caribou Provincial Park exert tremendous influence on woodland caribou habitat. However, they vary significantly in their ecological effects and return intervals. Fire severity plays an important role in determining both structure and composition of forest communities, shaping forest openings, duff characteristics, and how terrestrial lichen (an important food source for woodland caribou) recolonize an area after a burn. Results show that the amount of terrestrial lichen able to regenerate varies depending upon canopy openness and duff accumulation on V30 sites within Woodland Caribou Provincial Park. The amount of area burned within the park (measured by decade) in the 20th century varied dramatically from 319 ha in the 1950’s to over 106,000 ha in the 1980’s. These variations in site characteristics and stands of suitable ages have important implications for management and policy development. Forests suitable for woodland caribou habitat in this portion of Ontario are not in equilibrium. Land use policies intended to conserve caribou in this region must incorporate concepts of non-equilibrium forest dynamics. Management and policy development related to the conservation of woodland caribou is largely absent in Ontario Parks, due to a lack of information and limited strategic vision. The Forest Division of the Ontario Ministry of Natural Resources is making significant strides towards sustainable management of forests, but silvicultural constraints imposed by the sustained yield paradigm are limiting the management prescriptions attempting to mimic natural disturbances. Fire management continues to be problematic in both jurisdictions, as the cost of ecologically oriented management remains very high. Moreover, concepts of non-equilibrium forest dynamics have not been integrated into any land use management prescription, further limiting forest fire management. Adaptive management that integrates the complexity of this ecosystem at multiple spatial and temporal scales is necessary for effective long-term conservation of woodland caribou habitat in northwestern Ontario

Efficient computations in central simple algebras using Amitsur cohomology

We present an efficient computational representation of central simple algebras using Brauer factor sets. Using this representation and polynomial quantum algorithms for number theoretical tasks such as factoring and $S$-unit group computation, we give a polynomial quantum algorithm for the explicit isomorphism problem over number field, which relies on a heuristic concerning the irreducibility of the characteristic polynomial of a random matrix with algebraic integer coefficients. We present another version of the algorithm which does not need any heuristic but which is only polynomial if the degree of the input algebra is bounded.Comment: 24 pages. Comments welcome