Unreasonable influences one found in headquarters (6)

I believe the answer is:

biases

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'unreasonable influences' is the definition.
The definition and answer can be both related to thinking as well as being plural nouns.
Maybe you can see a link between them that I can't see?

'one found in headquarters' is the wordplay.
'one' becomes 'i' (Roman numeral).
'found in' is an insertion indicator.
'headquarters' becomes 'bases' (I've seen this before).
'i' put into 'bases' is 'BIASES'.

Can you help me to learn more?

(Another definition for biases that I've seen is " Prejudices, preconceptions".)

I've seen this clue in The Times.

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