Show Reference: "Does bimanual grasping of the Müller-Lyer illusion provide evidence for a functional segregation of dorsal and ventral streams?"

Does bimanual grasping of the Müller-Lyer illusion provide evidence for a functional segregation of dorsal and ventral streams? Neuropsychologia, Vol. 50, No. 14. (December 2012), pp. 3392-3402, doi:10.1016/j.neuropsychologia.2012.09.026 by Rachel M. Foster, Urs Kleinholdermann, Silke Leifheit, Volker H. Franz
@article{foster-et-al-2012,
    abstract = {Studies claiming a differential processing of visual illusions for perception and action have been subjected to many challenges. One criticism is that attentional demands were mismatched between the perception and action tasks. Dewar and Carey (2006) reexamined this argument by comparing bimanual grasping to bimanual size estimation and concluded that manual size estimation ({ManEst}) was affected by the illusion to a greater extent than grasping, supporting the case for two functionally distinct streams of visual processing. We tested whether this result may be due to their use of closed loop visual conditions by replicating their study under both closed and open loop conditions. We found that the difference in illusion effects between grasping and {ManEst} disappeared under open loop conditions, indicating that Dewar and Carey's findings can be explained by the availability of visual feedback and not a perception/action dissociation. We also discuss potential shortcomings of bimanual designs. \^{a}º Perception–action dissociation found with bimanual grasping under full vision. \^{a}º If vision is removed during grasping, the dissociation vanishes. \^{a}º Visual feedback during movement is critical, not a dorsal/ventral dissociation. \^{a}º Bimanual designs have the drawback that the hands' responses are not independent.},
    author = {Foster, Rachel M. and Kleinholdermann, Urs and Leifheit, Silke and Franz, Volker H.},
    doi = {10.1016/j.neuropsychologia.2012.09.026},
    issn = {00283932},
    journal = {Neuropsychologia},
    keywords = {biology, cue-combination, grasping, illusion, motor, perception},
    month = dec,
    number = {14},
    pages = {3392--3402},
    posted-at = {2013-07-04 17:27:48},
    priority = {2},
    title = {Does bimanual grasping of the {M\"{u}ller-Lyer} illusion provide evidence for a functional segregation of dorsal and ventral streams?},
    url = {http://dx.doi.org/10.1016/j.neuropsychologia.2012.09.026},
    volume = {50},
    year = {2012}
}

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A traditional model of visual processing for perception and action proposes that the two tasks rely on different visual representations. This model explains the weak effect of visual illusions like the Müller-Lyer illuson on performance in grasping tasks.

Foster et al. challenge the methodology used in a previous study by Dewar and Carey which supports the perception and action model of visual processing due to Goodale and Milner.

They do that by changing the closed visual-action loop in Dewar and Carey's study into an open one by removing visual feedback at motion onset. The result is that the effect of the illusion is there for grasping (which it wasn't in the closed-loop condition) but not (as strongly) for manual object size estimation.

Foster et al. argue that this suggests that the effect found in Dewar and Carey's study is due to continuous visual feedback.