Psychologists at the University of Canterbury have found natural disasters cause people to make more mistakes afterwards.
William S. Helton and James Head were working with people before and after the September earthquake in Canterbury.
The pair measured cognitive control by asking people to press a button matching numbers on a screen or withhold a response to a preselected number on the same screen.
The results showed people who were anxious following the quake responded more quickly and made more errors.
Those who were depressed logged slower response times.
The authors say this matches anecdotal reports of people saying they zoned out after an extreme experience and made more mistakes.
Mr Helton and Mr Head say the research could have implications for police and other emergency services responding to a disaster.
The findings will appear in the Anglo-American academic journal Human Factors.