Conditions Equivalent to Unit Representations of Ordered Relational Structures

This paper studies several concepts about subgroups of automorphisms of linearly ordered relational structures. In particular, it focuses on conditions that are equivalent to the translations (automorphisms with no fixed points plus the identity) forming a homogeneous, Archimedean ordered group under the asymptotic order. For the automorphisms of an ordered relational structure, these properties are equivalent to the structure having a numerical representation whose scale type lies between, but does not exclude, the ratio and interval types (Alper, 1987; Luce, 1987; Narens, 1981a, 1981b). One result of this paper (Theorem 5) is that for the automorphisms of an ordered relational structure the following necessary conditions for such a representation are also sufficient: the asymptotic order induced on the automorphisms is connected, the structure is homogeneous, the translations are Archimedean, and the dilations (i.e., automorphisms with fixed points) are Archimedean relative to all automorphisms. The last property is equivalent to there being at most one proper, nontrivial convex subgroup. Contrary to hope, these results do not seem to lead to a simpler proof than Alper's for the Dedekind complete case. The paper concludes with an examination of the structure of parallel automorphisms. Copyright 2001 Academic Press.     

Phonetic priming, neighborhood activation, and PARSYN

Perceptual identification of spoken words in noise is less accurate when the target words are preceded by spoken phonetically related primes (Goldinger, Luce, & Pisoni, 1989). The present investigation replicated and extended this finding. Subjects shadowed target words presented in the clear that were preceded by phonetically related or unrelated primes. In addition, primes were either higher or lower in frequency than the target words. Shadowing latencies were significantly longer for target words preceded by phonetically related primes, but only when the prime-target interstimulus interval was short (50 vs. 500 msec). These results demonstrate that phonetic priming does not depend on target degradation and that it affects processing time. We further demonstrated that PARSYN--a connectionist instantiation of the neighborhood activation model--accurately simulates the observed pattern of priming.     

Increased exposure and phonetic context help listeners recognize allophonic variants

This study examines the influence of increased exposure and phonetic context on the recognition of words that are produced with nasal flaps in American English (e.g., the word center produced as cenner). Previous work has shown that despite their high frequency of occurrence, words produced with nasal flaps are recognized more slowly and less accurately compared with canonical pronunciation variants produced with /nt/, which occur less frequently. We conducted two experiments in order to investigate how exposure and phonetic context influence this reported processing disadvantage for flapped variants. Experiment 1 demonstrated that the time to recognize flapped variants presented in isolation decreased over the course of the experiment, while accuracy increased. Experiment 2 replicated this finding and showed further that flapped variants that were presented in a casually produced sentence context were recognized faster compared with flapped variants presented in a carefully produced sentence context. Interestingly, the effect of context emerged only in late responses and was present only for flapped but not for canonical variants. Our results thus show that increased exposure and phonetic context help listeners recognize allophonic variants. This finding provides further support for the notion that listeners are flexible and adapt to phonetic variation in speech.