Yesterday Mr Key admitted he rang him to see if he was interested in finding out about the job and directed him to Maarten Wevers, head of the Department of Prime Minister and Cabinet.
He said he had not mentioned the phone call earlier, because "I'd forgotten that at that particular time".
Maryanne Garry, a Victoria University psychologist who specialises in real-life memory distortions, said it was plausible the Prime Minister was genuinely forgetful and not intentionally lying.
"Just because you forget something doesn't mean it's malevolent."
She said memory was like a plough that you had to use deeper and deeper to unearth all memories.
"Sometimes you have to have several passes through," she said.
"All he is doing is not remembering at the time he's trying to remember, then he does fairly quickly - so I wouldn't call that any kind of lying or conniving."
She said it had become fashionable in politics, particularly in the Clinton era, to use memory as an explanation for things.
"Now you will see people phrase things as, 'that is how I remember it', or 'to the best of my recollection', which places an out on the table.
"People can be wrong about the most amazing things - people can be wrong in spectacular ways," she said.
Memory bank:
John Key:
* Forgot how many Tranz Rail shares he owned.
* Unsure if and when he was briefed by GCSB on Kim Dotcom.
* Forgot how he voted on drinking age.
* Could not recall whether he was for or against the 1981 Springbok Tour.
* Could not remember who was aboard mystery CIA jet parked at Wellington airport.
* Forgot he phoned future director of GCSB urging him to apply for the job.
John Banks:
* Denied ever having met internet tycoon Kim Dotcom, or having a friendship with him, despite offering a toast to him at his birthday party.
* Forgot a political donation from Dotcom.
Hekia Parata:
* Told Parliament she had not been consulted by State Services Commissioner Iain Rennie before he accepted Education Secretary Lesley Longstone's resignation. She later corrected her answer to Parliament.
Labour leader David Shearer:
* Forgetting to disclose a bank account at New York City's Chase Manhattan Bank, with more than $50,000 in it.
Helen Clark:
* Kept it hidden for six months that Sir Owen Glenn had informed her he had given a donation to Winston Peters. She sat silently through Peters' subsequent public denials, his "no" sign, even the beginning of the privileges committee hearing into that donation.
- Additional reporting Adam Bennett of the New Zealand Herald
