Tunnel vision or general interference? Cognitive load and attentional bias are both important.

Accuracy of identification of single letters presented in the near periphery (2.2 degrees, 3.3 degrees, or 4.4 degrees) was adversely affected when subjects were given a simultaneous foveal visual task as part of the same display. The level of processing required by the foveal task as well as the attentional allocation instructions were both found to be important. Tunnel vision as opposed to general interference can be induced by a combination of high foveal cognitive load, a focused attention strategy, and speed stress.