It shouldn’t take you long to notice what’s wrong with this picture:
Obviously Nora is defying gravity in this shot — you can’t help but notice it. But in your first glance at the photo, how quickly do you notice what’s wrong? Do you spot the oddity faster than you’d notice Nora in the original, unaltered picture?
A 1978 study by Geoffrey Loftus and Norman Mackworth found that people respond quicker to unusual or inappropriate objects in line drawings, such as an octopus instead of a tractor in a farm scene. They moved their eyes an average of 7 degrees to fixate on the unusual objects. But in 1999, a team led by John Henderson found the opposite — people spotted a microscope in a bar scene no sooner than a cocktail glass in the same location, and only moved an average of 3 degrees from where they had been looking previously.
Why the discrepancy? It’s hard to know: Maybe, for example, Henderson’s team’s drawings were just too complicated for viewers to spot differences easily. Or perhaps a microscope in a bar is less unusual than an octopus on a farm. How can we ever measure what’s “more unusual” in a given context?
A team led by Mark Becker has developed a different way of inserting oddities into a scene. Instead of replacing one object with another, they altered parts of photos using Photoshop, as I did with the picture of Nora above. To reduce the chance of viewers looking for unusual parts of pictures, they had volunteers look at just two pictures: one altered scene and one unaltered one, from this set (if they saw the altered face, they saw the unaltered truck, and vice versa):
Ninety-four viewers’ eye movements were tracked as they fixated on a small cross in the middle of the screen, then viewed each picture for 8 seconds. Here are the results:
Whether people saw the altered truck photo or the group portrait, they fixated on the altered object significantly faster than the unaltered object. They also fixated on significantly fewer objects before moving to look at the altered object compared to the unaltered object. They moved their eyes an average of 8 degrees to the altered objects, suggesting that unusual objects can be located even when they are far from where we’re looking.
The team conducted a second experiment where the color of objects was modified — a man’s was turned green in one picture, and a stop sign was green in a second picture. In this case the results were mixed: while the hand-modification matched the results of the first experiment, there wasn’t as clear an advantage for the stop sign. As you can see from this picture, another object in each photo was modified to be green in the “unaltered” photos to make sure people weren’t simply attracted to the color green.
People not only looked at the green stop sign faster, they also looked at the green license plate faster than the unaltered license plate. But since in California where the study was conducted, plates are normally white, people may have seen the plate as just as “unusual” as a green stop sign.
So, this research suggests that we do notice unusual parts of a scene faster than “normal” parts of a scene. It’s also possible, the researchers say, that different types of unusual objects might do more (or less) to attract attention. Threatening things, disgusting things, faces, or other objects might each have a different weighting in the internal competition to attract our attention. But this study does make it clear that some objects definitely do attract attention faster than others.
Becker, M.W., Pashler, H., Lubin, J. (2007). Object-Intrinsic Oddities Draw Early Saccades.. Journal of Experimental Psychology: Human Perception and Performance, 33(1), 20-30. DOI: 10.1037/0096-15126.96.36.199