Multiple distance cues do not prevent systematic biases in reach to grasp movements
The perceived distance of objects is biased depending on the distance from the observer at which objects are presented, such that the egocentric distance tends to be overestimated for closer objects, but underestimated for objects further away. This leads to the perceived depth of an object (i.e., the perceived distance from the front to the back of the object) also being biased, decreasing with object distance. Several studies have found the same pattern of biases in grasping tasks. However, in most of those studies, object distance and depth were solely specified by ocular vergence and binocular disparities. Here we asked whether grasping objects viewed from above would eliminate distance-dependent depth biases, since this vantage point introduces additional information about the object’s distance, given by the vertical gaze angle, and its depth, given by contour information. Participants grasped objects presented at different distances (1) at eye-height and (2) 130 mm below eye-height, along their depth axes. In both cases, grip aperture was systematically biased by the object distance along most of the trajectory. The same bias was found whether the objects were seen in isolation or above a ground plane to provide additional depth cues. In two additional experiments, we verified that a consistent bias occurs in a perceptual task. These findings suggest that grasping actions are not immune to biases typically found in perceptual tasks, even when additional cues are available. However, online visual control can counteract these biases when direct vision of both digits and final contact points is available.
Compliance with ethical standards
Conflict of interest
Chiara Bozzacchi declares that she has no conflict of interest. Karl K. Kopiske declares that he has no conflict of interest. Robert Volcic declares that he has no conflict of interest. Fulvio Domini declares that he has no conflict of interest. Ethical approval: All procedures performed involving human participants were in accordance with the ethical standards of the institutional research committee (Comitato Etico per la Sperimentazione con l’Essere Vivente of the University of Trento) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent: Informed consent was obtained from all individual participants included in the study. Some of data described here have also been presented at the 2018 European Conference on Visual Perception.
- Brenner, E., & Smeets, J. B. J. (1997). Fast responses of the human hand to changes in target position. Journal of Motor Behavior, 29(4), 297–310.Google Scholar
- Campagnoli, C., & Domini, F. (2018). Depth-cue combination yields identical biases in perception and grasping. Manuscript submitted for publication.Google Scholar
- Domini, F., & Caudek, C. (2013). Perception and action without veridical metric reconstruction: An affine approach. In Shape perception in human and computer vision (pp. 285–298). London: Springer.Google Scholar
- Franz, V. H. (2003). Manual size estimation: a neuropsychological measure of perception? Experimental Brain Research, 151, 471–477.Google Scholar
- Glover, S., & Dixon, P. (2002). Dynamic effects of the Ebbinghaus illusion in grasping: Support for a planning/control model of action. Perception & Psychophysics, 64(2), 266–278.Google Scholar
- Goodale, M. A. (2011). Transforming vision into action. Vision Research, 51(13), 1567–1587.Google Scholar
- Goodale, M. A., & Milner, A. D. (1992). Separate visual pathways for perception and action. Trends in Neurosciences, 15(1), 20–25.Google Scholar
- Jeannerod, M. (1984). The timing of natural prehension movements. Journal of Motor Behavior, 16(3), 235–254.Google Scholar
- Jeannerod, M. (1986). The formation of finger grip during prehension. A cortically mediated visuomotor pattern. Behavioural Brain Research, 19, 99–116.Google Scholar
- Keefe, B. D., Hibbard, P. B., & Watt, S. J. (2011). Depth-cue integration in grasp programming: No evidence for a binocular specialism. Neuropsychologia, 49, 1246–1257. https://doi.org/10.1016/j.neuropsychologia.2011.02.047.Google Scholar
- Nicolini, C., Fantoni, C., Mancuso, G., Volcic, R., & Domini, F. (2014). A framework for the study of vision in active observers. In B. Rogowitz, T. Pappas, & H. de Ridder (eds.), Proceedings of the SPIE (Vol. 9014, p. 901414). San Francisco. https://doi.org/10.1117/12.2045459.
- R Core Team. (2015). R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing. https://www.r-project.org.
- Servos, P., Goodale, M. A., & Jakobson, L. S. (1992). The role of binocular vision in prehension: A kinematic analysis. Vision Research, 32(8), 1513–1521.Google Scholar
- Smeets, J. B. J., & Brenner, E. (1999). A new view on grasping. Motor Control, 3(3), 237–271.Google Scholar
- Whitwell, R. L., & Goodale, M. A. (2013). Grasping without vision: Time normalizing grip aperture profiles yields spurious grip scaling to target size. Neuropsychologia, 51(10), 1878–1887. https://doi.org/10.1016/j.neuropsychologia.2013.06.015.Google Scholar