Abstract
The manual estimation task requires that participants separate the distance between their thumb and forefinger until they perceive it to match the size of a target object. Ganel and colleagues (Curr Biol 18:R599–R601, 2008a) demonstrated that manual estimations yield just-noticeable-difference (JND) scores that linearly increased with increasing target object size; that is, responses adhered to Weber’s law and thus evince response mediation via relative and perception-based visual information. In turn, more recent work has reported that the size of a target object influences whether JNDs provide a reliable metric for evaluating the nature of the visual information supporting manual estimations. In particular, Bruno et al. (Neuropsychologia 91:327–334, 2016) reported that JNDs for ‘large’ target objects (i.e., 80 and 120 mm) violate Weber’s law due to biomechanical limits in aperture opening. It is, however, important to recognize that the absolute size of the ‘large’ target objects employed by Bruno et al. may have exceeded some participants’ functional aperture separation and resulted in a biomechanical strategy serving as the only viable response mode. Hence, the present investigation employed a manual estimation task wherein target object sizes were proportionately matched to decile increments (i.e., 10, 20, …, 70 and 80%) of individual participants’ maximal aperture separation. Results showed that JNDs increased linearly with increasing target object size. Accordingly, we propose that manual estimations of target objects within a functionally ‘graspable’ range adhere to Weber’s law and are mediated via relative and perception-based visual information.
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Notes
Bruno et al. (2016) do not employ the term just-noticeable-difference (i.e., JND); rather, the authors employ the term ‘variable error’. For consistency, and given the findings of the present work, we use JND as a standard term to reflect trial-to-trial variability in peak grip aperture.
As defined by Pheasant (1986), functional aperture separation is the distance at which an individual can grasp a flat wooden board with the tips of the thumb and ring finger to effectively lift, and is between 10 and 15% of an individual’s maximum aperture separation.
References
Aglioti S, DeSouza JF, Goodale MA (1995) Size-contrast illusions deceive the eye but not the hand. Curr Biol 5:679–685
Brainard DH (1997) The Psychophysics Toolbox. Spat Vis 10:433–436
Bruno N, Uccelli S, Viviani E, de’Sperati C (2016) Both vision-for-perception and vision-for-action follow Weber’s law at small object sizes, but violate it at larger sizes. Neuropsychologia 91:327–334
Cumming G (2013) Understanding the new statistics: Effect sizes, confidence intervals, and meta-analysis. Routledge, New York
Daprati E, Gentilucci M (1997) Grasping an illusion. Neuropsychologia 35:1577–1582
Davarpanah Jazi S, Heath M (2014) Weber’s law in tactile grasping and manual estimation: Feedback-dependent evidence for functionally distinct processing streams. Brain Cogn 86C:32–41
Davarpanah Jazi S, Heath M (2016) Pantomime-grasping: advance knowledge of haptic feedback availability supports an absolute visuo-haptic calibration. Front Hum Neurosci 10:197
Davarpanah Jazi S, Hosang S, Heath M (2015a) Memory delay and haptic feedback influence the dissociation of tactile cues for perception and action. Neuropsychologia 71:91–100
Davarpanah Jazi S, Yau M, Westwood DA, Heath M (2015b) Pantomime-grasping: the ‘return’ of haptic feedback supports the absolute specification of object size. Exp Brain Res 233:2029–2040
Ganel T, Chajut E, Algom D (2008a) Visual coding for action violates fundamental psychophysical principles. Curr Biol 18:R599–R601
Ganel T, Chajut E, Tanzer M, Algom D (2008b) Response: When does grasping escape Weber’s law? Curr Biol 18:R1090–R1091
Goodale MA (2011) Transforming vision into action. Vision Res 51:1567–1587
Goodale MA, Milner AD (1992) Separate visual pathways for perception and action. Trends Neurosci 15:20–25
Greiner TM (1991). Hand anthropometry of U.S. army personnel. United States Army Natick Research, Development and Engineering Center. Natick, MA
Haffenden AM, Goodale MA (1998) The effect of pictorial illusion on prehension and perception. J Cogn Neurosci 10:122–136
Heath M, Mulla A, Holmes SA, Smuskowitz LR (2011) The visual coding of grip aperture shows an early but not late adherence to Weber’s law. Neurosci Lett 490:200–204
Heath M, Holmes SA, Mulla A, Binsted G (2012) Grasping time does not influence the early adherence of aperture shaping to Weber’s law. Front Hum Neurosci 6: 332
Heath M, Davarpanah Jazi S, Holmes SA (2015) An inverse grip starting posture gives rise to time-dependent adherence to Weber’s law: a reply to Ganel et al. (2014). J Vis 15:1
Holmes SA, Heath M (2013) Goal-directed grasping: The dimensional properties of an object influence the nature of the visual information mediating aperture shaping. Brain Cogn 82:18–24
Holmes SA, Mulla A, Binsted G, Heath M (2011) Visually and memory-guided grasping: aperture shaping exhibits a time-dependent scaling to Weber’s law. Vision Res 51:1941–1948
Holmes SA, Lohmus J, McKinnon S, Mulla A, Heath M (2013) Distinct visual cues mediate aperture shaping for grasping and pantomime-grasping tasks. J Mot Behav 45:431–439
Hosang S, Chan J, Davarpanah Jazi S, Heath M (2016) Grasping a 2D object: terminal haptic feedback supports an absolute visuo-haptic calibration. Exp Brain Res 234:945–954
Loftus GR, Masson ME (1994) Using confidence intervals in within-subject designs. Psychon Bull Rev 1:476–490
Manzone J, Davarpanah Jazi S, Whitwell RL, Heath M (2017) Biomechanical constraints do not influence pantomime-grasping adherence to Weber’s law: a reply to Utz et al. (2015). Vis Res 130:31–35
Marks LE, Algom D (1998) Psychophysical scaling. In: Birnbaum MH (ed) Measurement, judgment, and decision making. pp 81–178 Press, Academic Press
Pedhazur EJ (1997) Multiple regression in behavioral research: Explanation and prediction. Harcourt Brace College Publishers, Orlando
Pheasant ST (1986) Bodyspace: Anthropometric ergonomics and design. Taylor and Francis, London
Smeets JB, Brenner E (2008) Grasping Weber’s law. Curr Biol 18:R1089–R1090
Utz KS, Hesse C, Aschenneller N, Schenk T (2015) Biomechanical factors may explain why grasping violates Weber’s law. Vision Res 111:22–30
Whitwell RL, Milner AD, Cavina-Pratesi C, Byrne CM, Goodale MA (2014) DF’s visual brain in action: the role of tactile cues. Neuropsychologia 55:41–50
Whitwell RL, Ganel T, Byrne CM, Goodale MA (2015) Real-time vision, tactile cues, and visual form agnosia: removing haptic feedback from a “natural” grasping task induces pantomime-like grasps. Front Hum Neurosci 9:216
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Supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada and Faculty Scholar and Major Academic Development Fund Awards from the University of Western Ontario.
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Heath, M., Manzone, J. Manual estimations of functionally graspable target objects adhere to Weber’s law. Exp Brain Res 235, 1701–1707 (2017). https://doi.org/10.1007/s00221-017-4913-8
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DOI: https://doi.org/10.1007/s00221-017-4913-8