Abstract
A cathode-ray oscilloscope and a Polaroid camera record interresponse times as a function of time, stimulus wavelength, and similar variables. Each response flashes a point of light on the oscilloscope screen; the vertical position of the point gives IRT, the horizontal position gives the value of the other variable. Several thousand such points may be recorded on a single frame of film, and the density of the points indicates the relative frequency of various IRTs. The method has the advantages of a two-dimensional display of continuous variables, flexibility, speed, and relatively low cost. It lacks the advantage of a digital output. Figures show IRTs of pigeons on VI, FR, DRL and extinction, and transitions among these, and also the results of stimulus generalization tests. The results have some provocative features that require much further exploration. Among other things, they suggest that "response rate" as a measure usually includes a response-dependent component that is insensitive to changes in other variables.