I have noticed an increasing trend in psychological writing whereby, perhaps either a) in a misguided attempt by those lacking a Classical education to sound 'posh', or b) in a misguided overgeneralisation by those who have just discovered that 'data' is plural, 'schema' is used as though it is the plural of the non-word 'schemum' rather than the singular of 'schemata' (or 'schemas': not strictly correct, but less pretentious). Worse, it is sometimes being used as an uncountable noun: one would never say 'I like writing letter', but one increasingly reads 'I like studying schema'. I know English is a flexible and constantly-developing language, but I hope not to the extent where illiteracy becomes permissible.