Secretory immunoglobulin A and cardiovascular activity during mental arithmetic: effects of task difficulty and task order.

Secretory immunoglobulin A (sIgA) in saliva and cardiovascular activity were measured at rest and during mental arithmetic. Task difficulty was manipulated by presenting easy, hard, and impossible versions of the mental arithmetic task in counterbalanced order, while task novelty was operationalised as order of presentation (i.e. first, second, third). Mental arithmetic elicited significant increases in sIgA concentration and sIgA secretion rate, as well as significant cardiovascular effects. Performance decreased and rated difficulty increased with increasing task difficulty. However, sIgA and cardiovascular activity, with the exception of diastolic blood pressure, were insensitive to variations in task difficulty. In contrast, sIgA concentration and a broad range of cardiovascular variables were influenced by task novelty, with more pronounced activity characterising the task version presented first, irrespective of its level of difficulty. Task novelty would seem to be a more important determinant of sIgA and cardiovascular activity than task difficulty.