Sidelong glances at sexy billboards while driving could get you into trouble with more than your wife, according to recent research.
These images momentarily block your ability to process information about your environment, which may increase the risk of an accident.
The research set out to examine the rubbernecking effect, where drivers slow down to look at car accidents. However, the scientists from Yale University and Vanderbilt University in Tennessee discovered that erotic images are even more distracting than gory pictures of violent injuries.
Volunteers were shown computer images of hundreds of landscapes or buildings thought to be emotionally neutral. They could see each picture for only a tenth of a second and were asked to spot a target picture that had been rotated.
All that participants had to do was identify which way the picture had been rotated. To make the task a bit more difficult, however, erotic or violent pictures had been hidden among them.
The pictures were organised so that either two or eight neutral scenes were presented between the erotic or violent image and the target picture. The closer these images were together, the less likely the participants were to be able to identify the target.
"We observed that people fail to detect visual images that appeared one-fifth of a second after emotional images, whereas they can detect those images with little problem after viewing neutral images," explains Dr David Zald, of Vanderbilt University.
"With the gory images, volunteers guessed the correct rotational direction around 75 per cent of the time, compared to 90 per cent of the time following more neutral images."
These findings are to be presented in Psychonomic Bulletin and Review.
Performance was even worse after the erotic images, according to more recent unpublished research by the group. "Volunteers were correct only about 60 per cent of the time, which is only a little better than would be expected by chance," says Zald.
The participants failed to spot the target pictures despite having been warned that distracting pictures would be included and instructed to ignore them. "This effect occurs even when participants have a financial incentive to perform well," says Zald.
It's well known that the visual short-term memory is limited. This means that images can be missed when we are paying close attention to something else. The new research indicates that we can also miss what we are searching for if we are shown an unexpected image that impacts us emotionally.
"We think there is essentially a bottleneck for information processing and, if a certain type of stimulus captures attention, it can jam up the bottleneck so subsequent information can't get through," says Zald.
"The results suggest that, if a person is driving and sees a crash or even an evocative billboard, the image may grab their attention and prevent them from processing information from their environment for a short time. If you're travelling at 120km/h, then you travel a long-distance in that quarter of a second."
Jerry Purcell, head of RAC Ireland, noted: "It wouldn't be good to have billboards by the roads that distract drivers. Thankfully, there are very few such billboards in Ireland to date".
Dr Vikki Burns is a scientist from the University of Birmingham on placement at The Irish Times as a Fellow of the British Association for the Advancement of Science Media