Symmetry limitations on quantum mechanical observers, and conjectured   link with string theory
  This paper tentatively conjectures a possible physical picture that may help explain links between quantum field theories and string theories. A correspondence might occur if the stringy parameters $\tau $ and $\sigma_i $ are interpreted as representing particular types of observer capabilities. Observer limitations could be imposed by symmetries of relevant quantum mechanical observer states. It is possible that this postulate may in future be able to go a small way towards understanding a physical basis for some of the dualities that have been found in string/field theory. 
M. Dance