PUPILLARY DILATION AS A MEASURE OF ATTENTION - A QUANTITATIVE SYSTEM-ANALYSIS

It has long been known that the pupil dilates as a consequence of atte ntional effort. But the function that relates attentional input to pup illary output has never been the subject of quantitative analysis. We present a system analysis of the pupillary response to attentional inp ut. Attentional input is modeled as a string of attentional pulses. We show that the system is linear; the effects of input pulses on the pu pillary response are additive. The impulse response has essentially a gamma distribution with two free parameters. These parameters are esti mated; they are fairly constant over tasks and subjects. The paper pre sents a method of estimating the string of attentional input pulses, g iven some average pupillary output. The method involves the technique of deconvolution; it can be implemented with a public-domain software package, PUPIL.