Recently, knowledge of the mechanisms of visual-spatial attention has improved due to studies employing single cell recording with alert monkeys and studies using performance analysis of neurological patients. These studies suggest that a complex neural network including parts of the posterior parietal lobe and midbrain are involved in covert shifts of visual attention. This paper describes two experiments employing the dual task technique to determine if covert visual orienting can take place while a person's attention is engaged in a language processing task. Results show clear evidence of interference between the two tasks suggesting a common system. The results also indicate that whatever is common to the two tasks does not have the same anatomical location as found for visual spatial attention. Previous work in cognitive psychology has also proposed a dissociation between the alerting and selective aspects of attention. In agreement with this dissociation the present study found that omitting any warning signal worsened performance for left-sided patients. These two patterns were also found in normals when we compare blocks run at a high state of alertness with those run at lower levels of alertness. These results support suggestions of a right sided bias for alerting but show that it is not the cause of the attentional selection deficit often reported in right parietal patients. A hierarchical distributed network is proposed to accommodate these data. (Author/JAZ)