No evidence of interference of hypocapnia/ respiratory alkalosis with classical conditioning of electrodermal responses

Most phobias can be traced to aversive experiences relating to the phobic cue, but most aversive experiences do not result in phobias. Why is it that only sometimes these experiences result in classical conditioning of fear? It was hypothesized that if the subject is in a state of hypocapnia/respiratory alkalosis, classical conditioning of fear is facilitated, while extinction of fear responses is inhibited. Thirty-two healthy volunteers underwent a classical conditioning procedure with slides as conditioned stimulus. Electric shocks as unconditioned stimulus, and electrodermal responding as (un) conditioned response. During conditioning, half of the subjects hyperventilated and were hypocapnic/alkalotic, while the other half was not. In both groups clear conditioning occurred, but there was no effect of hypocapnia. Results are critically discussed.