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A two-state model of simple reaction time

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- 88 -<br />

parameters <strong>of</strong> the distribution functions are suppressed, but<br />

the reader should not be confused by this notational simplification.<br />

- -<br />

Let R(x) =: 1 - R(x). That is, R(x) is the probability that<br />

the subject remains in Sp during more than x <strong>time</strong> units. Then,<br />

-R(t - x)· dD(x) is the probability that the subject enters into Sp<br />

at <strong>time</strong> x and be still in Sp at <strong>time</strong> t. The probability that the<br />

subject is in Sp at <strong>time</strong> t, P(t,T O )' can be expressed as follows,<br />

P(t, TO) =f,t< t - x), dD(x) (4-3)<br />

Now, let RT(x,t,T O ) be the distribution function <strong>of</strong> <strong>simple</strong><br />

RT when the stimulus is presented after <strong>time</strong> t has elapsed from<br />

the start <strong>of</strong> the trial.<br />

Then,<br />

RT (x , t ,TO) == P( t , TO) •Fp (x) +(l - P(t , TO» •Fnp(x)<br />

Hence, mean RT at <strong>time</strong> t, RT(t,T O )' is<br />

et:J<br />

RT(t,T O ) ;:=. J:,dRT(X,t,T O )<br />

00 00<br />

::; p(t, TO)' fox, dFp(x) +(l - p(t, TO» J;.dFnp(x)<br />

:::: P(t,TO)·RTPt(l- P(t,TO»·RTnp<br />

where RTp and RTnp are the mean RTs when the subject is in Sp<br />

or in Snp, respectively.<br />

(4-4)

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