### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 2pPP2. Noise discriminability. II. Leaky integrator models.

**Donald E. Robinson
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Martin E. Rickert
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*Dept. of Psych., Indiana Univ., Bloomington, IN 47405
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Several two-interval, same--different experiments involving the
discriminability of samples of noise have been reported previously. A striking
feature of these data is the effect of temporal position: samples that are
altered near the end are more discriminable than those in which the change
occurs earlier. This effect occurs over a wide range of durations and
bandwidths. Here two models are reported that describe these results. In each
model the waveforms from the two temporal intervals are jittered in amplitude,
filtered, and squared or rectified. In one model, the resulting waveforms are
passed through a leaky integrator and subtracted from one another. This
difference waveform is squared and passed through a second leaky integrator. A
sample of the output of the second-stage leaky integrator taken at the end of
the integration period is used as a decision variable from which hit and false
alarm rates are obtained and d[sup '] is computed. In the other model, the
squared waveforms are multiplied by an exponential weighting function before
subtraction. A signal-to-noise statistic is then used to obtain an estimate of
d[sup ']. The fitting parameters for each model are the variance of the internal
noise process and the time constant of either the second-stage integrator or of
the exponential weighting function. The results of simulations will be compared
with data from two experiments, and the relation of these models to others
involving leaky integrators will be discussed. [Work supported by AFOSR.]