Heterogenous scaling in interevent time of on-line bookmarking

In this paper, we study the statistical properties of bookmarking behaviors in Delicious.com. We find that the interevent time (τ) distributions of bookmarking decays powerlike as τ increases at both individual and population level. Remarkably, we observe a significant change in the exponent when interevent time increases from intra-day to inter-day range. In addition, dependence of exponent on individual Activity is found to be different in the two ranges. These results suggests that mechanisms driving human actions are different in intraand inter-day range. Instead of monotonically increasing with Activity, we find that inter-day exponent peaks at value around 3. We further show that less active users are more likely to resemble poisson process in bookmarking. Based on the temporal-preference model, preliminary explanations for this dependence have been given . Finally, a universal behavior in inter-day scale is observed by considering the rescaled variable τ/〈τ〉. PACS: 89.75.Da;05.45.Tp;02.50.Ey