Attentional blink (AB) is a phenomenon observed in rapid serial visual presentation (RSVP). When presented with a sequence of visual stimuli in rapid succession at the same spatial location on a screen, a participant will often fail to detect a second salient target occurring in succession if it is presented between 200–500 ms after the first one. Attentional blink was first described in 1992.
The precise adaptive significance behind the attentional blink is unknown, but it is thought to be a product of a two-stage visual processing system attempting to allocate episodic context to targets. In this two-stage system, all stimuli are processed to some extent by an initial parallel stage, and only salient ones are selected for in-depth processing, in order to make optimum use of limited resources at a late serial stage.
One curious aspect of attentional blink is that it usually includes "lag 1 sparing", meaning that targets presented very close together in time (at "lag 1" or consecutively in the RSVP stream) are not affected by the attentional blink, even though items presented at slightly greater lags are significantly impaired. There is as yet no conclusive explanation for the phenomenon of lag 1 sparing, although it is thought to be related to the first parallel stage of the two-stage system of stimulus selection and processing.
According to the LC-NE hypothesis, when a salient, or meaningful stimulus is presented, neurons in the locus coeruleus release norepinephrine, a neurotransmitter that benefits the detection of the stimulus. The effect of this release lasts for 100 ms after the salient stimulus is presented and benefits the second target when presented immediately after the first one, accounting for lag 1 sparing. Eventually the neurons in the locus coeruleus enter a refractory period, due to the auto-inhibitory effect of norepinephrine. According to the hypothesis, targets presented during this refractory period cannot trigger a release of norepinephrine, resulting in the attentional blink. The episodic distinctiveness hypothesis of the ST2 model suggests that the attentional blink reflects a limitation of the visual system attempting to allocate unique episodic contexts to the ephemeral target stimuli presented in RSVP.
The attentional blink can be moderated by changes in visual similarity between targets and distractor stimuli, but it can also be affected by conceptual similarities, suggesting that stimuli are processed to quite a deep level preconsciously, with much of the resulting information discarded before it reaches consciousness.
The attentional blink is related to, but distinct from the phenomenon of repetition blindness.
Recent research has also shown that when the second target (T2) in RSVP is an emotional word it is more likely to be perceived during the attentional blink. This research suggests that emotion mediates attention.
There have also been studies using images as emotional stimuli. Emotionally negative pictures preceding the target by 2 items were found to induce greater deficits in processing the target stimuli than neutral pictures did. Thus, it seems that emotional information can elicit attentional biases which temporarily prevent awareness of actively sought out stimuli. 
A study conducted by Heleen Slagter, Richard Davidson and colleagues, suggests that meditation, particularly vipassana, may reduce the duration of attentional blink. In an experiment, 17 people received three months of intensive training in meditation. Those 17 along with 23 meditation novices performed an attention task in which they successively picked out two numbers embedded in a series of letters. The novices exhibited attentional blink and missed the second number. In contrast, all the trained meditators consistently picked out both numbers. This indicated meditation practice can improve focus.
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- Biello, David (October 2007) Searching for God in the Brain Scientific American
- Scientific American video blog
- The Laboratory for Attention, Brain, and Behavior, led by Dr. Barry Giesbrecht, has published a number of studies addressing the attentional blink.
- Theory and instructions for attentional blink
- Computational Models of the Attentional Blink