Jakob Nielsen says that: Horizontal Attention Leans Left
While evidence from neuroscience, as described by Jeremy Tunnell (Product Manager for Stack Exchange) suggests that "the brain’s visual system is biased to the right of one’s focus":
Most of the text processing capabilities of the brain reside in the left hemisphere. This means that visual stimuli appearing on the right side of the visual field have a decided advantage.
In fact, information on the left side of the visual field has to enter the right hemisphere of the brain and be transferred through the corpus callosum to the left hemisphere – through two centimeters of callosal cable. As a result, words on the left side of the visual field are recognized more slowly and are subject to more errors.
Why does there appear to be a disconnect between the fields of neuroscience and usability on this question? Do you have any first-hand observations which can back-up one or the other propositions?