Attentional blink is a perceptual phenomenon where people presented with a rapid sequence of information may miss the second of two targets. For example, someone might be asked to identify letters in a string of numbers presented one by one. The first letter, an important target, would be caught by the study subject, but a second letter flashed seconds later might not be observed. There are a number of theories to explain how and why this works, and studies have explored its limitations and parameters to learn more about visual perception.
As the brain deals with a rapid stream of incoming information, it has to allocate processing resources to understanding, interpreting, and storing the information. The human brain is capable of considerable processing power for complex tasks, but even it has limitations. Attentional blink is an example that has important implications for people working in environments where they may be inundated with information. An airport baggage screener, for instance, might see a knife in one bag, but could miss a second knife in another that moves through immediately afterward, unless the equipment is calibrated to accommodate attentional blink.
One theory involves the neurological processes involved in perception. People looking for specific targets in a stream of information experience a burst of neurotransmitters when they spot a target. The cells that emit these neurotransmitters need to recover, in what is known as the refractory period. This period may be short, but can be long enough to miss a second stimulus. Attentional blink lasts around half a second, lending credence to this hypothesis.
Other researchers suggest there may be a perceptual capacity issue. A number of processes are involved in visual perception and processing, and coordinating these across the brain can take a toll. People dealing with complex stimuli may not be able to handle them all. Studies on attentional blink have utilized tools like meditation to determine if it’s possible to increase focus and perceptual accuracy, and some suggest that this is the case, indicating that brains could potentially be trained to expand their perceptual abilities.
An interesting exception to this rule was documented in a Journal of Experimental Psychology article published in 2008, where researchers found that faces didn’t appear to be subject to attentional blink. The face is often an exception to rules of perception, which may be because it is of critical importance in recognizing other humans and interacting with them successfully. People need to be able to read facial cues in conversation, for example, and would be ill-served if they couldn’t catch signs of emotions on the face of a conversation partner.