A parametric model for time-intensity curves

We present a phenomenological parametric model for time-intensity (T-I) curves. The rising and decaying parts of the curve are described by logistic curves. The logarithm of their product models the sensory response. A crucial feature of the model is its ability to fit the long straight tails often seen in T-I data, as well as plateaus of arbitrary length. The parameters of the model have a straightforward correspondence to the shape of the curve. We discuss fitting of the model, show results for experimental data and show how systematic patterns of deviations from the prototypical T-I curve shape lead to directions for extension of the model.