A Taxonomy of Attention77Annu. Rev. Psychol. 2011.62:73-101. Downloaded from Access provided by Columbia University on 08/25/15. For personal use only.
and separate. The taxonomy simply reflects thefact that relevant studies can be grouped arounda certain set of issues and questions, such thatpaper citations would be clustered. The goal isnot to strictly segregate the different topics ofattention, but rather to organize them betterso that connections between areas of study willbecome more clear.External AttentionExternal attention to the perceptual world canbe subdivided according to the focus of atten-tion. First, attention can be directed to one orseveral modalities, separable from each otherduring initial neural processing. Second, in-dependent of modality, attention is deployedover space and over time, with separate issuesto consider for spatial versus temporal atten-tion. In addition, attention can be allocated overspace, time, and modality according to stim-ulus features or how they are organized intoobjects. These dimensions are not exclusive ofeach other, but they represent useful ways toorganize the mechanisms of attention, and theyrepresent lines along which studies have beenconducted.Modality.Sensory processing is initially sep-arate for the five modalities of vision, hearing,touch, smell, and taste. Attention serves toselect and modulate processing within each ofthe five modalities, and it directly impacts pro-cessing within relevant sensory cortical regions.Although the bulk of research reviewed andcategorized in this taxonomy stems from thevisual attention literature, these findings gener-alize well to the other modalities. For example,attention to visual stimuli enhances discrimina-tion and activates relevant topographic areas inretinotopic visual cortex (Tootell et al. 1998),allowing observers to detect stimuli at lowercontrast or to make finer discrimination. Atten-tion to sounds enhances processing in auditorycortex (Woldorff et al. 1993), allowing listenersto detect fainter sounds or to discriminate finerpitch differences. Similar effects of attentionoperateinsomatosensorycortex,olfactorycortex, and gustatory cortex ( Johansen-Berg& Lloyd 2000, Veldhuizen et al. 2007, Wageret al. 2004, Zelano et al. 2005).One goal of research is to clarify howindependent these systems are and how theyinteract. These different systems appear tooperate separately with independent capacity—an inference that can be made by showingthat multiple signals coming from the samemodality interfere more with each other thando signals coming in from across differentmodalities (Arnell & Jolicoeur 1999, Duncanet al. 1997, Potter et al. 1998). Interferencebetween modalities appears to occur at a morecentral stage of processing.