Attentional selection of noncontiguous locations: the spotlight is only transiently "split".

It is still a matter of debate whether observers can attend simultaneously to more than one location. Using essentially the same paradigm as was used previously by N. P. Bichot, K. R. Cave, and H. Pashler (1999), we demonstrate that their finding of an attentional "split" between separate target locations only reflects the early phase of attentional selection. Our subjects were asked to compare the shapes (circle or square) of 2 oddly colored targets within an array of 8 stimuli. After a varying stimulus onset asynchrony (SOA), 8 letters were flashed at the previous stimulus locations, followed by a mask. For a given SOA, the performance of subjects at reporting letters in each location was taken to reflect the distribution of spatial attention. In particular, by considering the proportion of trials in which none or both of the target letters were reported, we were able to infer the respective amount of attention allocated to each target without knowing, on a trial-by-trial basis which location (if any) was receiving the most attentional resources. Our results show that for SOAs under 100-150 ms, attention can be equally split between the two targets, a conclusion compatible with previous reports. However, with longer SOAs, this attentional division can no longer be sustained and attention ultimately settles at the location of one single stimulus.

[1]  Mark M Schira,et al.  Interactions between task difficulty and hemispheric distribution of attended locations: implications for the splitting attention debate. , 2005, Brain research. Cognitive brain research.

[2]  C. Eriksen,et al.  Effects of noise letters upon the identification of a target letter in a nonsearch task , 1974 .

[3]  H. Pashler,et al.  Evidence for split attentional foci. , 2000, Journal of Experimental Psychology: Human Perception and Performance.

[4]  Y. Tsal.  Movements of attention across the visual field. , 1983, Journal of experimental psychology. Human perception and performance.

[5]  G. Rizzolatti,et al.  Reorienting attention across the horizontal and vertical meridians: Evidence in favor of a premotor theory of attention , 1987, Neuropsychologia.

[6]  J. Theeuwes,et al.  Parallel allocation of attention prior to the execution of saccade sequences. , 2003, Journal of experimental psychology. Human perception and performance.

[7]  Patrick Cavanagh,et al.  The blinking spotlight of attention , 2007, Proceedings of the National Academy of Sciences.

[8]  George Sperling,et al.  The spatial distribution of visual attention , 2004, Vision Research.

[9]  C. Eriksen,et al.  Allocation of attention in the visual field. , 1985, Journal of experimental psychology. Human perception and performance.

[10]  Takashi R Sato,et al.  Neuronal Basis of Covert Spatial Attention in the Frontal Eye Field , 2005, The Journal of Neuroscience.

[11]  M. Posner,et al.  Attention and the detection of signals. , 1980, Journal of experimental psychology.

[12]  S. A. Hillyard,et al.  Sustained division of the attentional spotlight , 2003, Nature.

[13]  N. P. Bichot,et al.  Visual selection mediated by location: Feature-based selection of noncontiguous locations , 1999, Perception & psychophysics.

[14]  J Driver,et al.  A selective review of selective attention research from the past century. , 2001, British journal of psychology.

[15]  Fred H Hamker,et al.  Modeling feature-based attention as an active top-down inference process. , 2006, Bio Systems.

[16]  F. Crick.  Function ofthethalamic reticular complex: Thesearchlight , 1984 .

[17]  F. K. Berrien,et al.  The effects of noise. , 1946, Psychological bulletin.

[18]  C. Eriksen,et al.  Visual attention within and around the field of focal attention: A zoom lens model , 1986, Perception & psychophysics.

[19]  J. Townsend.  Serial vs. Parallel Processing: Sometimes They Look like Tweedledum and Tweedledee but they can (and Should) be Distinguished , 1990 .

[20]  Qing Yang,et al.  The latency of saccades, vergence, and combined eye movements in children and in adults. , 2002, Investigative ophthalmology & visual science.

[21]  F. Hamker.  A dynamic model of how feature cues guide spatial attention , 2004, Vision Research.

[22]  Heiner Deubel,et al.  Properties of attentional selection during the preparation of sequential saccades , 2007, Experimental Brain Research.

[23]  Z W Pylyshyn,et al.  Tracking multiple independent targets: evidence for a parallel tracking mechanism. , 1988, Spatial vision.

[24]  A. Kramer,et al.  Splitting the Beam: Distribution of Attention Over Noncontiguous Regions of the Visual Field , 1995 .

[25]  D. LaBerge.  Spatial extent of attention to letters and words. , 1983, Journal of experimental psychology. Human perception and performance.

[26]  F. Crick.  Function of the thalamic reticular complex: the searchlight hypothesis. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[27]  Patrick Cavanagh,et al.  Distinguishing models of multifocal attention: It's a matter of time , 2010 .

[28]  D. Somers,et al.  Processing Efficiency of Divided Spatial Attention Mechanisms in Human Visual Cortex , 2005, The Journal of Neuroscience.

[29]  D. Somers,et al.  Multiple Spotlights of Attentional Selection in Human Visual Cortex , 2004, Neuron.

[30]  Robert M. McPeek,et al.  Saccades require focal attention and are facilitated by a short-term memory system , 1999, Vision Research.

[31]  F. Hamker.  The reentry hypothesis: the putative interaction of the frontal eye field, ventrolateral prefrontal cortex, and areas V4, IT for attention and eye movement. , 2005, Cerebral cortex.

[32]  K. Nakayama,et al.  Fixation offset facilitates saccades and manual reaching for single but not multiple target displays , 2007, Experimental Brain Research.

[33]  Chi-Hung Juan,et al.  Dissociation of spatial attention and saccade preparation. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[34]  O. Tzeng,et al.  Segregation of visual selection and saccades in human frontal eye fields. , 2008, Cerebral cortex.

[35]  J. Mattingley,et al.  Neurodisruption of selective attention: insights and implications , 2005, Trends in Cognitive Sciences.