Post-reinforcement pause in grocery shopping: comparing inter-purchase time across products and consumers

Abstract: Reinforcement usually generates an immediate pause in responding, which is followed by an increase in response probability as time since the last reinforcement increases. Considering that human activities can be interpreted in the light of these findings, the present paper examined purchase probability as a function of inter-purchase time. Panel data, based on a sample of 80 consumers purchasing nine supermarket food products during 16 weeks, obtained from a commercial firm, were initially used. For each product category, inter-purchase time (across all consumers) was very similar for each shopping occasion and purchase probability increased as a direct function of the logarithm of time since the last purchase. A comparison (Anova) of inter-purchase times across products and consumers showed that average inter-purchase time differed across four subsets of products and across seven groups of consumers, showing also a significant interaction effect. A correlation (Pearson) between individual inter-purchase time and number of products bought on each shopping occasion indicated that consumers that shop more frequently buy larger number of products per occasion (r (76) = -.54, p < .000). The same analyses were also conducted with a larger data set. These results have several managerial implications and demonstrate the usefulness of a behavior-analytic framework to the interpretation of consumer behavior