text: G*π*= − E 
  (cid:124)  − E 
  (cid:124) 
  q( ˜o,˜s|*π*)[ln q( ˜s| ˜o,*π*) − ln q( ˜s|*π*)] 
  (cid:123)(cid:122) 
  (cid:125) 
  Information gain  q( ˜o|*π*)[ln p( ˜o|C)] 
  (cid:125) 
  (cid:123)(cid:122) 
  Pragmatic value 
  
  (17) 
  
  The expression above shows how minimising the EFE leads to a natural balance between 
  information gathering and realising preferences. The first term on the right-hand side is the 
  change in belief from the prior to the posterior under a given policy called the epistemic 
  value or information gain. Optimising this value is what leads to (notably non-random) 
  exploratory behaviour. The second term is the pragmatic value; minimising this value 
  ensures that observations are in accordance with the preference prior**C**. 
  Another way to express the EFE is in terms of risk and ambiguity: 
  
  G*π*= E 
  (cid:124) 
  (18) 