Adaptation to delayed auditory feedback

Delayed auditory feedback disrupts the production of speech, causing an increase in speech duration as well as many articulatory errors. To determine whether prolonged exposure to delayed auditory feedback IDAFI leads to adaptive compensations in speech production, 10 subjects were exposed in separate experimental sessions to both incremental and constantdelay exposure conditions. Significant adaptation occurred for syntactically structured stimuli in the form of increased speaking rates. After DAF was removed, aftereffects were apparent for all stimulus types in terms of increased speech rates. A carry-over effect from the first to the second experimental session was evident as long as 29 days after the first session. The use of strategies to overcome DAF and the differences between adaptation to DAF and adaptation to visual rearrangement are discussed.     

Vowel recognition: Inferences from studies of forward and backward masking

The recognition of brief vowels was studied in forward and backward masking tasks. In a series of experiments in which both target and mask parameters were systematically varied, two populations of subjects were identified. The majority (Nonmaskers) evidenced little masking at any interstimulus interval, while relatively fewer subjects (Maskers) evidenced backward masking (but not forward masking) over a 100-200 ms interval. Increasing target set size systematically increased masking for the Maskers but not for the Nonmaskers. Adding white noise to the targets increased the extent of masking for both groups. These results suggest (1) that masking does not impose a substantive constraint on vowel perception in running speech, and (2) that multiple strategies may exist for vowel recognition.     

Book reviews

Wyer, Robert S., Jr. Cognitive Organization and Change : an Information Processing Approach. Potomac, Maryland: Lawrence Erlbaum Associates. 1974. Pp. 502. £10.50.

Egan, J. P. Signal Detection Theory and ROC Analysis. New York: Academic Press. 1975. Pp. 277. £9.75. ISBN

Aldis, O. Play-Fighting. New York: Academic Press. 1975. Pp. 319. £8.75.

Warburton, D. M. Brain Behaviour and Drugs. London: John Wiley. 1975. Pp. 280. £6.95. ISBN 0471 91991 8.

Grieve, D. W., Miller, D., Mitchelson, D., Paul, J. and Smith, A. J. Techniques for the Analysis of Human Movement. London: Lepus Books. 1975. Pp. 177. £5.50.     

Discrimination of time intervals marked by brief acoustic pulses of various intensities and spectra

Experienced observers were asked to identify, in a four-level 2AFC situation, the longer of two unfilled time intervals, each of which was marked by a pair of 20-msec acoustic pulses. When all the markers were identical, high-level (186-dB SPL) bursts of coherently gated sinusoids or bursts of band-limited Gaussian noise, a change in the spectrum of the markers generally did not affect performance. On the other hand, for 1-kHz tone-burst markers, intensity decreases below 25 dB SL were accompanied by sizable deterioration of the discrimination performance, especially at short (25-msec) base intervals. Similarly large changes in performance were observed also when the two tonal markers of each interval were made very dissimilar from each other, either in frequency (frequency difference larger than 1 octave) or in intensity (level of the first marker at least 45 dB below the level of the second marker). Time-difference thresholds in these two latter cases were found to be nonmonotonically related to the base interval, the minima occurring between 40- and 80-msec onset separations.     

Peripheral information extraction: A developmental examination of reading processes

Three experiments examining the information extraction processes are presented. In Experiments I and II, adults and children were presented paragraphs to read and search for specified targets, respectively. Two types of typographical (spatial) manipulations were used: case of the letters within the paragraphs was as normally experienced, or in alternating upper and lower case letters. Spacing between words was either as normal, filled with a neutral symbol, or absent. The response measures were reading and search speed in words per minute. Sensitivity to case (word shape) and space (word boundary) increased as a function of experience and was different for reading compared with search. In Experiment III subjects were asked to judge whether briefly presented pairs of letters were the same or different. Retinal (spatial) location was varied from trial to trial; dependent measure was reaction time. Results showed a developmental progression in response time with complex interactions. Theoretical interpretations of these data are discussed in support of the initial stage of Hochberg's peripheral to cognitive search guidance model.     

A comparison of frequency, interval, and time-sampling methods of data collection

Data representing high, medium, and low response rates in constant and nonconstant patterns were generated by electromechanical equipment to determine whether the same data collected by time-sampling, interval recording, and frequency recording would be represented similarly by each method. Results indicated: (1) that time-sampling provided an extremely inaccurate estimate of responding, and (2) that interval recording accurately represented responding of low and medium rates, but grossly underestimated high-rate responding.     

Facilitating paper recycling: effects of prompts, raffles, and contests

The effects of prompts and reinforcement to promote paper recycling were compared in six university dormitories. For a Prompt condition, residents were urged to recycle paper for ecological reasons via flyers distributed to each room. For a Raffle contingency, residents were given one raffle ticket for every pound of paper brought to a collection center. For a Contest contingency, two dorms were paired and the dorm whose residents delivered the most paper won $15 for its treasury. Contingency awareness was strengthened via a flyer placed under the door of each resident's room. Flyers alone had little effect in increasing paper-recycling behaviors, but the raffle (substantially) and the contest (somewhat) increased the amount of paper brought to a dorm's recycling center. Students whose rooms were closest to the collection center showed the greatest participation. Removal of the reinforcement contingencies resulted in a return to baseline levels.