(1) The most basic discrimination procedure:
CS- is simply paired with the omission of the UCS.

 

  CS+   gif gif   UCS
(Becomes
Inhibitory)
CS-    gif gifno UCS

 

 

(2) An alternative procedure in which CS2 becomes inhibitory because the UCS
is omitted on occasions when CS2 is present at the same time as CS1,
which by itself precedes the UCS.
 

   CS1   gif gif   UCS
(Becomes
Inhibitory)
CS1  
CS2  
gifgifno UCS

 

 

Two procedures for producing inhibitory conditioning
(after Davey, 1989, figure 2.2 page 32).