## The Scalar Timing Model Scalar TimingTheory

At each time unit (here taken as 1-sec intervals) the model determines whether a left lever response should occur. The value in the accumulator is equal to the clock speed multiplied by the clock time. The decision rule is based on the absolute value of the difference between the value of the sample from memory (m) and the accumulator value (a), divided by the value of the sample from memory (m). If this discrepancy is less than some threshold (b), a response will occur as illustrated in Figure 1.4.

If food is given, the value of the accumulator (multiplied by a random variable k*) will be put into memory. The memory storage constant (k*) is a random sample of one value from a normal distribution with some fixed mean and standard deviation. The speed of the clock is redetermined from a random sample from a normal distribution with some fixed mean and standard deviation; one item in memory is selected at random; and the threshold (b) is redetermined from a random sample from a normal distribution with some fixed mean and standard deviation. The indication that food was delivered is cleared, and the cycle clock is reset. In addition, responses occur at an operant rate of one response per 100 sec.

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