  A mass of traces of human activities show diverse dynamic patterns. In this
paper, we comprehensively investigate the dynamic pattern of human attention
defined by the quantity of interests on subdisciplines in an online academic
communication forum. Both the expansion and exploration of human attention have
a power-law scaling relation with browsing actions, of which the exponent is
close to that in one-dimension random walk. Furthermore, the memory effect of
human attention is characterized by the power-law distributions of both the
return interval time and return interval steps, which is reinforced by studying
the attention shift that monotonically increase with the interval order between
pairs of continuously segmental sequences of expansion. At last, the observing
dynamic pattern of human attention in the browsing process is analytically
described by a dynamic model whose generic mechanism is analogy to that of
human spatial mobility. Thus, our work not only enlarges the research scope of
human dynamics, but also provides an insight to understand the relationship
between the interest transitivity in online activities and human spatial
mobility in real world.
