Fallible Counters and Time

Arizona State University, Scottsdale AZ

Investigators

Abstract

Abstract When we judge the magnitude of a stimulus-the brightness of a light, heaviness of a weight, or duration of a sound-we are mapping that aspect onto another dimension, typically a numerical one. Even when comparing two stimuli directly, that comparison may be mediated by a neural representation akin to counting. A counter is a neural device that adds sensory action potentials, or, in the case of time, pacemaker pulses. Inaccuracies reveal the structure of the counter: Proportional error in sensory discriminations - Weber's law or scalar timing - is the most general laws of psychophysics; All models of counters must yield it. Minuscule deviations from it and from linear timing further strongly constrain candidates. Models of failure modes of counters will be developed and tested. Examples are: Failing to set a higher bank (e.g., 10's) when a lower one resets (the Y2K glitch); failing to reset; conditioning of weights in other than a power series. These will be compared to data collected on the discriminative and productive abilities of rats and pigeons, in particular: (1) mean performances in discriminating and producing temporal intervals; (2) Weber functions; (3) count distributions and hitting-times. Alternate weighting schemes for the accumulator that arise from conditioning will be studied. These schematic models will be integrated with realistic neural networks. The likelihood of this theory will compared with those of other current timing theories given these data. Results will be applied to information transmission and signal detection theories.