Even with unimpaired vision, observers sometimes fail to see things right before their open eyes. A typical example is the attentional blink effect, a period in which observers are unable to detect a target item in a sequence of stimuli, for as long as the previous one occupies their mind. Having considered a range of mechanisms proposed to explain attentional blink effect, we arrive at our preferred explanation, which ascribes the effect to a contextually motivated imbalance in the allocation of attentional resources between earlier and later target information. We interpret in this perspective our data on how the attentional blink effect changes as a result of practice.