A new study has revealed how our brains can form first impressions quickly.
Scientists at the University of Edinburgh and the Aix Marseille Universite examined why volunteers who were shown hundreds of pictures, some with animals and some without, were able to detect animals in as little as one-tenth of a second.
They found that one of the first parts of the brain to process visual information, the primary visual cortex, can control this fast response, rather than more complex parts of the brain being required, as previously thought.
The findings suggest that when people look at a scene for the first time, the brain's immediate responses can categorise it based on small areas of shape and texture. Other parts of the brain then use more complex processing, which takes longer, to work out the objects being seen.
The discovery could help inform the development of image-based internet search engines, by enabling computer programmes to classify images according to their geometry. It was previously thought that complex parts of the brain were required for analysing images, with categories, such as animals, only being detectable at a late stage in the process.
Researcher James Bednar said that these results have far-reaching implications for explaining people's sensory experience. They show that whenever people open their eyes, enter a room or go around a corner, they can quickly get the gist of a scene, well before figuring out exactly what they are looking at.
The study appears in Scientific Reports.
