Cross-modal selective attention: On the difficulty of ignoring sounds at the locus of visual attention

in three experiments, we investigated whether the ease with which distracti ng sounds can be ignored depends on their distance from fixation and from a ttended visual events. In the first experiment, participants shadowed an au ditory stream of words presented behind their heads, while simultaneously f ixating visual Lip-read information consistent with the relevant auditory s tream, or meaningless "chewing" lip movements. An irrelevant auditory strea m of words, which participants had to ignore, was presented either from the same side as the fixated visual stream or from the opposite side. Selectiv e shadowing was less accurate in the former condition, implying that distra cting sounds are harder to ignore when fixated. Furthermore, the impairment when fixating toward distracter sounds was greater when speaking lips were fixated than when chewing lips were fixated, suggesting that people find i t particularly difficult to ignore sounds at locations that are actively at tended for visual lipreading rather than merely passively fixated. Experime nts 2 and 3 tested whether these results are specific to cross-modal links in speech perception by replacing the visual lip movements with a rapidly c hanging stream of meaningless visual shapes. The auditory task was again sh adowing, but the active visual task was now monitoring for a specific visua l shape at one location. A decrement in shadowing was again observed when p articipants passively fixated toward the irrelevant auditory stream. This d ecrement was larger when participants performed a difficult active visual t ask there versus fixating, but not for a less demanding visual task versus fixation. The implications for cross-modal links in spatial attention are d iscussed.