How interviews are contaminated

When people are asked to recall something ‘on demand’, there is usually an agenda – the person asking the questions is looking for particular sorts of answers: who did they see? what did he look like? what did the doctor say? for instance. Because of this agenda, interviewers tend to hop about from one sort of information to another which means the interviewee can’t search their own store and all its connections in their own time.

Questions are also often closed – ‘Do you remember the video you saw?’ leading – ‘You remember the video about the operation, don’t you?’, and fast paced so there is no time to think. Sometimes they are even misleading, which happens when the interviewer thinks they know the answer but they are wrong, so the interviewee is being asked to agree with something that is not true.

Why does this matter? With most people, it doesn’t unless they feel intimidated. Research shows that people who feel that way or under threat will often agree with anything to escape the situation.  This is how false confessions happen. It is also true for people with mental vulnerabilities such as intellectual disability, dementia, acquired brain damage, or mental health problems where learning, memory, attention, or recall are impaired. These people need special consideration because

  • They acquiesce (say yes) to closed questions.
  • They produce less information the more questions are asked.
  • They are more suggestible so they incorporate new information – such as the misleading element of a closed question – and think they have remembered it. Then so does the interviewer!
  • They often pick the second of any two choices: ‘Was he standing on the left or the right?’
  • They think the interviewer already knows the answers so they try to guess what they want to hear.

Asking questions in this way certainly gets answers and quite quickly, but you will not be able to trust them. A typical interview can be over in minutes:

‘You know you’re going into hospital on Monday?’


‘And the doctor is going to do an operation on your eye?’


‘Then you’ll be able to see better.’


‘So you’d like him to do that, then?’


On the next page, we will look at ways of avoiding this and getting better quality information from people.

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