Many of these traders for the Institutions know one another and or the trading habits of many other individuals and or Institutions etc. and occasionally will even play with one another while trying to accomplish their assigned goal. A trade here or there is even a signal that one has spotted the other and is watching and or approving of the actions made by the other etc. When the action is less intense or a client has what they were looking for the individual traders assigned to the case moves onto other regular business or onto another case for a different client of the Institution... Old Joe