Abstract
Perisaccadic target-flash mislocalization can vary according to where the flash is presented, e.g., a flash occurring near the saccade starting point tends to be mislocalized in the direction of the saccade, whereas a flash occurring beyond the saccade end point tends to be mislocalized in the opposite direction. Such findings have been interpreted as reflecting a compression of visual space. Different studies, however, show differences in the time course of the compression. For example, the studies by Honda (1993) and Atwater & Lappe (2006) show maximum compression just after the saccade, whereas the study by Morrone, Ross & Burr (1997) shows maximum compression around the onset of the saccade. Recently, I proposed a model suggesting that some of the main characteristics of compression arise from an extraretinal signal whose onset time varies systematically across the retina (Pola, VSS 2007). One feature of the model is that the perceived location of a flash comes from flash retinal signal persistence interacting with the extraretinal signal (Pola, 2004). Another is that the perceived location of one flash can be influenced by the perceived location of a second flash by way of persistence, especially if the time interval between the two flashes is less than the duration of the persistence (Pola, 2007). In the present work, this model is used to provide an account of differences in compression from one study to another: The main features of compression may come from the way in which the extraretinal signal varies across the retina (see above). However, some of the differences in compression may be a consequence of different background stimuli, where perceived flash location is affected by persistence interacting with these stimuli. Taking into account background stimuli and re-plotting data, a number of differences between the studies are markedly reduced.