Our brains can detect when an object is a type of food in as little as 108 milliseconds. A better understanding of how we visually perceive food could help steer advertising towards encouraging us to make healthier choices.
Scientists know very little about how we process seeing food, says at the University of Sydney, Australia. “This is unexpected given the significant role vision plays in food selection,” he says. “For our ancestors, vision was the primary sense used for distant foraging, since senses like smell have limited range in humans.”
To learn more, Carlson and his colleagues had 20 people look at various images of different food and non-food items. The electrical activity of each person’s brain was monitored via an electroencephalogram.
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Some of the electrical activity data was used to train machine-learning models, with a unique model for each participant. Their brains would probably respond similarly to the various images, but the researchers wanted the models to be tuned to each individual, says Carlson.
Once trained, the researchers used the remaining data to test if the models could identify signatures of electrical activity that were linked to the participants seeing food. They also wanted to see if this activity differed between them seeing processed foods – defined as those that have been manipulated by people, such as pizza and sausages – and natural foods, such as fruits and vegetables.
To do this, the researchers then selected 314 images that the participants hadn’t seen before, which included natural and processed foods, as well as non-food items, such as socks and hammers. These were shown to them in six sets of 157 images, with each set lasting about 24 seconds and varying the order of the images. This was repeated six times for each of the participants, who were told to focus on a dot in the middle of the images.
The machine-learning models picked up on electrical activity signatures that were unique to the participants seeing food of some type. They also flagged signatures that varied when they saw natural or processed foods.
All of these brain signatures appeared between 108 and 116 milliseconds after seeing the images. “It takes 40 to 60 milliseconds for information to go from the retina to the cortex, so it’s not much longer after that that we’re seeing this response,” says Carlson.
Better understanding the visual aspects of how people perceive food could help them make more nutritious picks, he says. “Visual cues often guide our food choices, such as when we’re navigating a supermarket, looking at advertisements or seeing posts about food on social media.” With many advertisements being visual, “vision is key for influence”, says Carlson.
bioRxiv
