Monolingual speakers of Japanese were trained to identify English /r/ and /l/ using Logan et al.'s [J. Acoust. Soc. Am. 89, 874-886 (1991)] high-variability training procedure. Subjects' performance improved from the pretest to the post-test and during the 3 weeks of training. Performance during training varied as a function of talker and phonetic environment. Generalization accuracy to new words depended on the voice of the talker producing the /r/-/l/ contrast: Subjects were significantly more accurate when new words were produced by a familiar talker than when new words were produced by an unfamiliar talker. This difference could not be attributed to differences in intelligibility of the stimuli. Three and six months after the conclusion of training, subjects returned to the laboratory and were given the post-test and tests of generalization again. Performance was surprisingly good on each test after 3 months without any further training: Accuracy decreased only 2% from the post-test given at the end of training to the post-test given 3 months later. Similarly, no significant decrease in accuracy was observed for the tests of generalization. After 6 months without training, subjects' accuracy was still 4.5% above pretest levels. Performance on the tests of generalization did not decrease and significant differences were still observed between talkers. The present results suggest that the highvariability training paradigm encourages a long-term modification of listeners' phonetic perception. Changes in perception are brought about by shifts in selective attention to the acoustic cues that signal phonetic contrasts. These modifications in attention appear to be retrained over time, despite the fact that listeners are not exposed to the /r/-/l/ contrast in their native language environment.

The effects of variations in response categories, subjects' perception of natural speech, and stimulus range on the identification of American English /r/ and /l/ by native speakers of Japanese were investigated. Three experiments using a synthesized /rait/-/lait/ series showed that all these variables affected identification and discrimination performance by Japanese subjects. Furthermore, some of the perceptual characteristics of /r/ and /l/ for Japanese listeners were clarified: (1) Japanese listeners identified some of the stimuli of the series as /w/. (2) A positive correlation between the perception of synthesized stimuli and naturally spoken stimuli was found. Japanese listeners who were able to easily identify naturally spoken stimuli perceived the synthetic series categorically but still perceived a /w/ category on the series. (3) The stimulus range showed a striking effect on identification consistency; identification of /r/ and /l/ was strongly affected by the stimulus range, the /w/ identification less so. This indicates that Japanese listeners tend to make relative judgments between /r/ and /l/.

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It has been reported (1) that being exposed to the American English (AE) speaking environment in adulthood has less of an effect on the perception of AE /r/ and /l/ sounds for native speakers of Japanese than experience at younger ages, and (2) that laboratory training of those sounds on adult-Japanese has little effect. Recently, however, Logan et al. [J. S. Logan et al., J. Acoust. Soc. Am. 89, 874–886 (1991)] and Lively et al. [J. Acoust. Soc. Am. (1993)] showed that identification training with natural tokens produced by multiple talkers was effective in improving Japanese listeners ability to identify /r/ and /l/. In the present paper, the effect of extended training was examined. Subjects were adult native speakers of Japanese with no experience in living abroad. The training procedure was identical to Lively et al.’s procedure, except that subjects were trained for 45 sessions and were given two midterm tests. The results showed that (1) most of the subjects, even those whose score was around 60% in the pre-test, improved to more than 85% correct in the post-test, (2) some of the subjects kept improving throughout the 45 training sessions, while the others met asymptote with less training, and (3) the training effect in all the subjects generalized to the identification of new words produced by both familiar and unfamiliar talkers. The results are discussed in the context of recent theories of perceptual learning and development of phonological categories. [Work supported by ATR.]

In contrast to Japanese adults trained with stimuli produced by five talkers,

The restructuring of a non-fractal particle aggregate in simple shear flow was simulated by Stokesian dynamics approach. We studied the deformation and the resultant strength change of aggregate by surrounding flow under the condition that the cohesive strength of aggregate is comparable with the fluid stress. In particular, we focused on how the aggregate deteriorates due to the fluid stress exerted on it periodically. The image analysis was applied to visualized simulation results for quantitative estimation of irreversible change in aggregate configuration.We examined the structural change of aggregate from various perspectives, i.e., the outer shape, the internal strength and the fluid stress on the surface of the aggregate. The simulation results show that the aggregate gets squashed after intricate restructuring process and it elongates along with streamline as experimentally observed in the previous study. Regarding the internal strength, the weakest point locally develops in the aggregate by periodically-varying fluid stress. Combination of rotation and elongation effects of shear flow is complexly-involved in the deterioration of internal strength of aggregate.

Reversal of early ischemic injury on diffusion-weighted MRI (DWI) occurs rarely. In a stroke patient who abruptly developed stupor and left hemiparesis, DWI scanned 78 min after onset demonstrated a large ischemic injury in the right hemisphere with a DWI-ASPECTS (Albert Stroke Program Early Computed Tomography Score) of 5 points, although baseline brain CT was perfectly normal. MR angiography (MRA) showed an occlusion of the right middle cerebral artery trunk, and the patient received intravenous thrombolysis 105 min after onset. A second MRA 30 h later showed complete vessel recanalization, and DWI demonstrated a perfect reversal of the initial large ischemic injury, associated with very small thrombus-fragmented cortical surface infarctions. Outcome at 3 months was a modified Rankin Scale score of 0, and the fluid-attenuated inversion recovery image showed only a small final infarction at the cortical surface. Hyper-acute DWI-defined large ischemic injury may very rarely represent a nearly perfect reversible area, and it may be a therapeutic target.

Experiments are described that designed to investigate how Japanese subjects develop criteria for ‘‘R’’–‘‘L’’ decisions. Subjects were asked to identify English words beginning with /r/ and /l/ in two conditions: blocked (all words produced by one talker) and mixed (words produced by several talkers). Subjects performed more accurately in the blocked condition than in the mixed condition. This indicates that, as is generally true for native-language perception, stable talker characteristics facilitate non-native speech perception. Subjects also exhibited preferences for ‘‘R’’ or ‘‘L’’ responses for some talkers in one condition, but the opposite or no preference in the other. Together, these results indicate that in the blocked condition, subjects adopted talker-specific criteria. However, when the talker changed randomly in the mixed condition, subjects were not able to adjust their criteria for each talker, but apparently based their criteria upon the range of all /r/s and /l/s they heard. Thus subjects made more responses based on the ‘‘R’’ category for some talkers, and more based on ‘‘L’’ for others. The implications for theories of perceptual normalization and non-native speech perception will be discussed.