A computational experiment on elicitation task bias in time preference

Experimental results from research on time preference are often controversial. We propose a systematic investigation of choice task in multiple price list (MPL) format, frequently used for experiments on time preference, based on a computer simulation analysis. We conduct experiments with artificial subjects to demonstrate that elicited discount rates are highly dependent on the structure of elicitation task. We verify that implementing the choice task in MPL with nominal structure, provides observations of hyperbolic discounting. Choice task in MPL with interest rates structure leads to elicitations of discount rates compatible with exponential discounting. Moreover, we show that the magnitude and intensity of the corresponding data patterns depend on the internal structure of the elicitation task. Comparison between discount rates elicited with artificial and human subjects suggests that the behavior of human subjects in experiments with MPL can be described by the simple rules of positive discounting and anchoring. Experimental procedures related with MPL setting has to take into account the results and modify the task accordingly.