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The detectability of brief, 1000-Hz sinusoids added in phase or in quadrature to a continuous tonal masker (pedestal) of the same frequency as the signal was examined in the presence of a continuous wide-band noise. The effects of signal duration, shape of the signal's energy-density spectrum, sound-pressure level (SPL) of the pedestal, and noise spectrum level were investigated. For conditions in which the background noise level was low, two unusual phenomena were noted: (1) a complete absence of the customary trading relation between signal power and duration; and (2) an extremely shallow masking function relating signal SPL and pedestal level. These departures from the law of temporal integration and Weber's law are consistent with a simple filter model of the ear in which it is assumed that the location of the auditory filter is altered in response to changes in the parameters of the signal and masker. A basic assumption of the model is that the location of the filter is changed in order to maximize the ratio of signal energy to masker energy at the output of the filter. For detection of a tonal signal in the presence of another sinusoid, it appears that observers can listen at frequencies far removed from that of the signal, where signal energy is as much as 40 dB down from the peak.

An instructional unit was developed to enhance the critical thinking skills of middle school and high school students with learning disabilities by teaching them the principles of scientific reasoning. Student-teacher dialogues were used to engage the students in an active process of critical inquiry. Students analyzed everyday information presented in brief magazine articles and advertisements by applying the principles of the scientific method. The students made statistically significant improvements in their ability to (a) identify the principal claim made in an article or advertisement, (b) graph the relevant data, and (c) evaluate the claims made in the article and explain their support or rejection of the claims based on data. After the instructional unit, the overall performance of the special education students exceeded that of a control group composed of regular education students who had not received instruction in critical thinking.

No abstract

The effects of an interference tone on frequency discrimination of a brief tonal signal were investigated. The interference tone was 500 msec in duration and the same intensity as the signal. Changes in frequency discrimination were measured as a function of signal duration, the frequency separation between the interference tone and signal, and the temporal delay between the two. Both ipsilateral-and contralateral-interference conditions were investigated. The addition of an interference tone significanfiy degraded preformance in only one condition: 10-msec signal, trailing interference tone delivered to signal ear. For all other stimulus configurations, frequency discrimination was unaffected by the presence of the interference tone. These data are generally consistent with analogous sensory masking effects characterizing backward and forward masking and do not support cognitive-perceptual models of pitch and recognition.