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Interviewing intoxicated witnesses
Don’t be short-sighted about alcohol myopia
Many psychologists, including myself, are likely to recommend investigators wait until intoxicated individuals sober up before interviewing them about events they have witnessed.
We are also likely to caution that you’re not likely to get much of value from an impaired witness because alcohol tends to limit cognitive abilities such as attention to details and the processing of information. Such advice would likely be based upon research showing that alcohol impairs memory; albeit, for simple stimuli such as a list of words.
However, new research published in
All participants were first asked to sit at a “bar” and watch the experimenter prepare beverages. Participants in the alcohol group were given vodka and cranberry drinks, resulting in a breath alcohol concentration of 0.06 to 0.08 g/200L some 30 to 40 minutes after intake (which was based on gender and weight). Those in the placebo group were led to believe they were given the same alcoholic drink – they were not. The control group drank cranberry juice.
Each participant was later taken to a different room and asked to write down all that they could remember about the bar. Breath alcohol concentration was taken again to ensure the participants in the alcohol group met the legal definition of intoxication. A short while later, the participants witnessed a staged theft – a laptop being stolen from the room – and listened to a one-sided telephone conversation between the experimenter and a university employee about the theft. Then there was a twist! Half the participants in each of the three conditions were exposed to a telephone conversation that contained misinformation about the event.
The researchers then tested memory performance for each participant (by recording the percentage of correct, false, uncertain and ‘I don’t know’ responses, accuracy rate and number of words reported). To test the misinformation effect (erroneous information provided to participants after the event ended), the researchers measured the number of misinformation items provided from the telephone conversation.
Their main analysis of the data showed no difference between the alcohol, placebo or control groups on memory performance. That is, when compared against sober individuals, intoxicated participants did not provide significantly less correct information, more false information, more ‘I don’t know’ responses and were no more uncertain in their statements. Moreover, they found evidence of a misinformation effect – those exposed to misinformation reported more than those not exposed – but the intoxicated individuals did not report greater levels of post-event misinformation than sober individuals.
Another interesting finding from their study pertained to interview format. Compo and colleagues found that using a cued-interview format resulted in more false information being reported from intoxicated individuals than their sober counterparts.
Their findings suggest intoxicated individuals are not likely to have greater memory impairments or be more susceptible to adopting misinformation than their sober counterparts. It seems they are as good eyewitnesses as sober individuals – at least when on the lower limit of intoxication. The authors argue that their counterintuitive findings can best be explained through the theory of “alcohol myopia.”
When intoxicated, people have a limited attention system that focuses upon central information and ignores peripheral information. Intoxicated individuals are not able to attend to all relevant situational information so they are more likely to be influenced by the salient cues in a given situation (e.g., someone being injured) at the expense of weaker cues (e.g., the colour of a shirt).
Overall, the findings suggest that it may be possible to get as much complete and accurate information from intoxicated individuals as you can from teetotalers.
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