This study examined whether intensive mental training can affect one of the major capacity limits of information processing in the brain: the brain's limited ability to process two temporally close meaningful items. Using performance in an attentional-blink task and scalp-recorded brain potentials, we found, as predicted, that 3 mo of intensive mental training resulted in a smaller attentional blink and reduced brain-resource allocation to the first target, as reflected by a smaller T1-elicited P3b. Of central importance, those individuals that showed the largest decrease in brain-resource allocation to T1 generally showed the greatest reduction in attentional-blink size. These novel observations indicate that the ability to accurately identify T2 depends upon the efficient deployment of resources to T1 and provide direct support for the view that the attentional blink results from suboptimal resource sharing [5
]. Importantly, they demonstrate that through mental training, increased control over the distribution of limited brain resources may be possible.
Because participants did not engage in formal meditation during task performance, the observed reduction in T1 capture after 3 mo of intensive meditation suggests that purely mental training of certain attention skills can influence performance on a novel task that calls upon those skills. Green and Bavelier [10
] reported that intensive action video-game playing can improve attention skills, as reflected by enhanced performance on new cognitive tasks, including the attentional-blink task. Here, we show that improvements in performance of a novel, external task may also be achieved by pure mental training. As such, our findings extend previous research showing that the adult human brain is capable of plastic change in response to environmental stimulation (e.g., [8
]). Note that it is unlikely that motivational differences between groups can explain our findings, because previous work has shown that motivating participants to do well on an attentional-blink task by paying them according to their performance does not affect the magnitude of the attentional blink [17
]. In addition, the current findings corroborate previous findings in expert meditators [6
] by showing longitudinally, within subjects, that attention processes are flexible skills, which can be enhanced through mental training. The observed reduction in T1 capture after 3 mo of intensive Vipassana meditation training confirms first-person reports that this style of meditation affects attentional processes and can significantly affect the way stimuli are processed and perceived. Future longitudinal studies are needed to examine how long effects of mental training on attention may persist and whether even shorter-term training may demonstrably benefit various attentional skills.
Although they differ in the specific mechanisms, cognitive accounts of the attentional blink have generally held that there is a capacity-limited stage in stimulus processing and that competition between different stimuli for limited processing resources underlies the attentional-blink deficit (e.g., [18
]). In line with this idea, several recent brain-potential studies have shown that the ability to accurately identify T2 is related to the latency and/or amplitude of the T1-elicited P3b [5
]. A delayed or larger T1-evoked P3b was observed in trials in which T2 was missed versus seen [16
] and in individuals exhibiting a relatively large attentional blink [5
]. In addition, the amplitude of the T1-evoked P3b has recently been shown to be dependent on T1 probability and T1 cue validity [22
]. Together, these findings indicate that variability in the duration or difficulty of the T1 task (as indexed by T1-elicited P3b amplitude) may affect the severity of the competition between T1 and T2. In the current study, the magnitude of decrease in T1-elicited P3b amplitude over time in no-blink trials predicted the magnitude of decrease in attentional-blink size over time. This observation provides important additional support for the idea that the ability to accurately identify two temporally close, meaningful items depends upon the efficient deployment of resources to the first item [4
]. Beyond this, the current study indicates that through mental training, people may gain some control (which need not be voluntary) over the amount of attentional resources devoted to the processing of the first item.
Vipassana meditation allegedly reduces ongoing mental noise in the brain, enabling the practitioner to remain in the present moment. Three months of intensive training in this style of meditation may therefore have decreased mental capture by any stimulus, i.e., distracters and targets alike [5
], resulting in reduced distracter interference. Although we cannot fully exclude the possibility that reduced distracter interference may have contributed to our findings, mental training-related effects were not observed outside of the time window of the T1-elicited P3b, including the time window of the T2-elicited P3b. This observation supports the idea that intensive mental training selectively reduced brain-resource allocation to T1. Intensive mental training may, however, have affected relatively early T2-related processes; In trials in which the T1-elicited P3b was not confounded by neural activity associated with T2 (i.e., long-interval trials and T2-absent trials), a mental training-related reduction in posterior positivity was only observed for the early phase of the T1-elicited P3b (around 400 ms post-T1), but—in contrast to short-interval T2-present trials—not for its later phase (around 500 ms post-T1). The timing of this later effect (i.e., 152–215 ms post-T2) concurs with effects observed in a recent brain-potential study [16
]. This study elegantly showed that brain events occurring as early as 170 ms post-T2 were affected by the conscious perception of T2. Three months of intensive mental training may therefore not only have reduced T1 capture, but may have also influenced relatively early T2-elicited processes. The current findings allow us to speculate on candidate brain structures that intensive Vipassana meditation training may affect. Previous neuroimaging studies have implicated a network of frontal, parietal, and temporal brain areas in the generation of the scalp-recorded P3b [23
]. Activation of a similar network of brain areas has been associated with conscious target processing in the attentional-blink task [24
]. Three months of intensive mental training may thus have affected the recruitment of this distributed neural network.
In summary, the results presented here are consistent with the idea that the ability to accurately identify T2 depends upon the efficient processing of T1. They furthermore demonstrate that, through mental training, increased control over the allocation of limited processing resources may be possible. Our study corroborates the idea that plasticity in brain and mental function exists throughout life, and illustrates the usefulness of systematic mental training in the study of the human mind.