Image credit: Tom Caswell (CC BY 2.0)
How do you decide what to do next? Your behavior at any given moment is usually the result of a competition between internal and external factors. Internal factors include your existing plans, goals and knowledge. External factors include events happening in the world around you. When out driving, for example, you check zebra crossings because you know that pedestrians could be present. But you look at stoplights because your eyes are drawn automatically to their changing colors.
Scientists can study this competition between internal and external factors using a simple laboratory task. A single spot of light appears in the dark, and your job is to look away from it. The instruction is simple and yet carrying it out requires willful effort. This is because your automatic response is to look at any stimulus that suddenly appears. Overcoming this automatic response requires similar thought processes to those that help someone resist eating that second piece of chocolate.
However, the competition between automatic and voluntary visual processes is over in a fraction of a second, which makes it difficult to analyze. Salinas et al. therefore modified the “look-away” task by asking participants to respond under time pressure. This tweak makes it possible to track – with millisecond precision – voluntary and automatic influences on performance. The results revealed that the eyes are automatically drawn to the cue about 100 milliseconds after it appears. The separate voluntary process that directs the eyes away from the cue arises about 40 milliseconds later.
Salinas et al. observed these voluntary and involuntary components in every healthy volunteer tested. But there were also differences between individuals in how effectively they could look away from the cue. This is important because the automatic draw of salient stimuli determines what you pay attention to, as well as what you look at. Future studies could use the modified version of the look-away task to examine whether this automatic pull of attention, and the ability to resist it, differs in individuals with disorders like ADHD.
