In Chinese, verbs can be reduplicated. The form for reduplicated monosyllabic verbs is "AA' or " A-A". However, the form for reduplicated bisyllabic verbs is "ABAB", and "一“cannot be added between the two syllables of bisyllabic verbs. For example: 看看, 说说,等一等,数一数,介绍介绍,etc.
Reduplicating a verb has the function of implying a short duration for that action or the idea of giving something a try. In this sense, it is similar to adding"一下“ to the verb. --(From NPCR 2)