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We explore the recent finding (Newman & Dell, 1978) that the time needed to detect a target phoneme in a phoneme monitoring task is increased when the preceding word contains a phoneme similar to the target. Normal adult native speakers of English monitored auditorily presented sentences and responded as quickly as possible whenever they detected a specified phoneme. We found that preceding word-initial phonemes, despite being processed more quickly, increased the response latency to the following target phoneme more than did preceding word-medial phonemes. There was also an increase in response latency even when the subject could be highly certain that the similar preceding phoneme was not an instance of the target phoneme. We argue that the interference effects are due to fundamental characteristics of perceptual processing and that more time is needed to categorize the target phoneme. We present a computer simulation using an interactive activation model of speech perception to demonstrate the plausibility of our explanation.

The recent use of the tail-tip bleeding approach in mice has enabled researchers to generate detailed pulse and surge profiles of luteinizing hormone (LH) secretion in mice. However, the analysis of pulsatile LH secretion is piecemeal across the field with each laboratory using their own methodology. We have reformulated the once popular PULSAR algorithm of Merriam and Wachter to operate on contemporary computer systems and provide down-loadable and on-line pulse analysis platforms. As it is now possible to record the activity of the GnRH pulse generator in freely-behaving mice, we have been able to unambiguously define LH pulses in intact and gonadectomized male and female mice. These data sets were used to determine the appropriate PULSAR parameter sets for analysing pulsatile LH secretion in the mouse. This was then used to establish an accurate model of estrogen negative feedback in the mouse. Intact and ovariectomized mice given Silastic capsules containing 1, 2 and 4 µg 17-β-estradiol/20 gm body weight were tail-tip bled at 6-min intervals and the resultant LH profiles analysed with PULSAR. Only the 4 µg 17-β-estradiol capsule treatment was found to return LH pulse amplitude and frequency to that of intact diestrous mice. Ultra-sensitive mass spec analysis showed that the 4 µg 17-µ-estradiol capsule generated circulating estradiol levels equivalent to that of diestrous mice. It is hoped that the reformulation of PULSAR and generation of a realistic model of estrogen negative feedback will provide a platform for the more uniform assessment of pulsatile hormone secretion in mice.

The study confirmed the feasibility of using regular, computer-based quizzes for in-course assessment of a large medical school class and demonstrated assessments of a kind that would be difficult to achieve by means other than with computers.