I loved the movie Up. I particularly enjoyed Dug, the dog with the voice box that translated his thoughts into words. During a conversation, Dug would suddenly interrupt himself by yelling: "SQUIRREL!" He would then orient toward that little moving rodent and watch. Eventually, he resumed his conversation. For a week after seeing the movie, various members of my family would interrupt conversations with the sudden cry of "Squirrel!" It's still good for the occasional laugh.
I was reminded of the movie when walking with our family dogs recently. I'm glad they don't have voice boxes. If they did, they would constantly be interrupting our walks with cries of squirrel or bird or rabbit! The attention of our dogs is easily captured by small moving animals. The cry of "Squirrel!" seems to really capture how attention works in both real and cartoon dogs.
Squirrel also describes how attention works for the rest of us. Perhaps with respect to attentional capture, we aren't so different from dogs (although clearly we differ in other cognitive capacities - see Dogs Don't Remember). Like dogs, our attention is easily captured by small moving objects: squirrels in the woods, flies in the kitchen.
Clearly there are evolution-selected mechanisms at work here. For example, attentional capture is also driven by fear-relevant items. When researchers present pictures and ask people to search for various objects, a snake amongst flowers is more quickly noticed than a flower amongst snakes. Even young children who have never encountered snakes find the snake more rapidly - Vanessa LoBue and Judy DeLoache have investigated the developmental aspects of attention for fear relevant objects.
Attentional capture is a flexible system, however, rather than one with an innate reflex structure that is completely set. We've all learned to respond quickly to at least one personally relevant stimulus - our names. Imagine you are at a gathering and having a conversation with someone. Another person in a nearby conversation says your name. Even though you had no idea what those people were talking about, your attention was captured by your name (this is generally called the Cocktail Party Effect although it works in all sorts of gatherings). Once you notice your name, your attention moves to that other conversation - just like a dog orienting toward a squirrel.
The attentional capture system also responds to addiction related objects. Recently, I was talking with a colleague who smokes. He stated that he often has problems locating some items, such as his car keys, on his very busy desk. His cigarettes, however, appear to quickly jump out from the same surroundings. Several researchers have studied attention bias and addiction objects in recent years. All concur that addiction objects bias attention (I'll write more about attention and addiction later).
Attentional capture doesn't always work, unfortunately. If you are really focused on some demanding activity, then you may fail to notice all sorts of interesting things that pass directly in front of you - like unicycling clowns (see Unicycling Clowns, Train Wrecks, and Pilots Forgetting to Land). Failing to notice something because of focused attention is called inattentional blindness. There is a battle for control of your conscious experience between focused attention, inattentional blindness, and attentional capture. What will capture and hold your attention?
Dug, the Up dog, cracks me up. His repetitive attentional capture by small moving rodents reminds me of my dogs (and my own attentional capture). Our attention can easily be captured by various stimuli in our surroundings. Squirrel!