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Working memory deficit could lead to rape

Crossing the line Men who have a low ability to process multiple pieces of information are more likely to go too far in sexual encounters, a new study suggests.

The study of the link between working memory capacity and sexual decision making could explain why only some men who are aroused by rape scenarios, actually act out their fantasy, says clinical psychologist Dr Amy Lykins at the University of New England.

For a man to force a woman to have sex, at some stage he must make the decision to continue regardless of negative feedback he is getting from the woman.

This decision involves weighing up positives such as satisfying his sexual desire, with negatives such as possibly being convicted of rape.

Lykins and colleagues investigated the role of working memory capacity in influencing how a man weighs up such short-term and long-term consequences of his actions.

Working memory capacity determines the amount of information we can hold in our brain at one time for processing. It is a key part of 'executive functioning', which is our ability to take in information about the world and process it to make the best decisions.

"It's basically how we regulate our behaviour," says Lykins.

Working memory capacity assessment

In a study published in this month's issue of the journal Archives of Sexual Behaviour, Lykins and colleagues assessed the working memory capacity of 59 male volunteers by getting them to complete sentences and then recall the words they generated.

"They had to remember the words generated for two sentences right up to six sentences," says Lykins.

The researchers also measured arousal levels in the men when they were shown images of consensual and non-consensual sexual encounters.

As a proxy for sexual arousal, Lykins and colleagues looked at skin conductance response, which measures changes in electrical activity in the skin.

"Higher activity means higher physiological arousal," says Lykins.

She and colleagues also measured how long each study participant looked at each image.

Date rape scenario

Finally, the researchers played the participants a recording of a scenario in which a man forces himself on a woman despite her repeatedly saying 'no'.

After listening to the scenario, the participants were given the script with numbered dialogue lines, and asked to specify at which line they thought the average Australian male would stop all advances.

Lykins says because of the taboo involved in rape, this was considered a more accurate way of probing the participants' views than asking where they themselves would stop.

"Other research has shown that people attribute other people's behaviours as similar to their own so it was a proxy measure," she says.

Later stopping point

The researchers found that participants who were aroused by the non-consensual sexual images and viewed the images for longer on average nominated a later stopping point in the date rape scenario than those who were not aroused.

But when they looked closer, the participants who stopped later were only those had low to moderate working memory capacity.

"Our working memory capacity measure did have a moderating effect on the relationship between how aroused they were and the stopping point," says Lykins.

She says this conclusion is supported by the fact that people who had high arousal to the non-consensual images, but also high working memory capacity, stopped at the same point as those who had low arousal to the images.

Study limitation

Lykins says one limitation of the study is that sexual arousal was not measured directly.

However, she says the skin conductance response was most likely measuring sexual arousal, versus disgust or distress, because those with the higher arousal measures had later stopping points. Also, these men viewed the images for longer, says Lykins, suggesting they found the images pleasurable.

Lykins says this paper is one of the first to look at cognitive factors involved in sexual decision making.

Previous research has focused on the influence of external factors such as alcohol, which is understood to increase the risk of non-consensual sex as a result of "alcohol myopia".

"Alcohol narrows people's attention down to the positive consequences of behaviour rather than the potentially negative consequences, specifically related to sexual activity," says Lykins.

She says it would be interesting for future research to study how factors such as alcohol interact with working memory capacity to influence sexual decision making.