Abstract
A number of studies have reported that grasps and manual estimations of differently sized target objects (e.g., 20 through 70 mm) violate and adhere to Weber’s law, respectively (e.g., Ganel et al. 2008a, Curr Biol 18:R599–R601)—a result interpreted as evidence that separate visual codes support actions (i.e., absolute) and perceptions (i.e., relative). More recent work employing a broader range of target objects (i.e., 5 through 120 mm) has laid question to this claim and proposed that grasps for ‘larger’ target objects (i.e., >20 mm) elicit an inverse relationship to Weber’s law and that manual estimations for target objects greater than 40 mm violate the law (Bruno et al. 2016, Neuropsychologia 91:327–334). In accounting for this finding, it was proposed that biomechanical limits in aperture shaping preclude the application of Weber’s law for larger target objects. It is, however, important to note that the work supporting a biomechanical account may have employed target objects that approached —or were beyond—some participants’ maximal aperture separation. The present investigation examined whether grasps and manual estimations differentially adhere to Weber’s law across a continuous range of functionally ‘graspable’ target objects (i.e., 10,…,80% of participant-specific maximal aperture separation). In addition, we employed a method of adjustment task to examine whether manual estimation provides a valid proxy for a traditional measure of perceptual judgment. Manual estimation and method of adjustment tasks demonstrated adherence to Weber’s law across the continuous range of target objects used here, whereas grasps violated the law. Thus, results evince that grasps and manual estimations of graspable target objects are, respectively, mediated via absolute and relative visual information.
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Notes
The term just-noticeable-difference (i.e., JND) was not employed by Bruno et al. (2016). Instead, the authors used 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.
Skewness and interquartile range (IQR) statistics were computed via the MATLAB Statistics Toolbox (7.9.0 The MathWorks, Natick, MA, USA). The skewness statistic was bias corrected and the equation documentation can be found at: https://www.mathworks.com/help/stats/skewness.html. The interquartile range represented the mid-spread or middle 50% of all values for a given participant and object size combination and was computed as the difference between the 75th (Q 3) and 25th (Q 1) percentiles (i.e., Q 3 minus Q 1).
Skewness for each object size was contrasted to zero. Given the number of comparisons, Fig. 5 depicts 99% between-participant confidence intervals to prevent inflation of our experiment-wise error rate. Notably, however, even when a more liberal confidence interval (i.e., 95% confidence interval) was adopted the only reliable difference was that the grasping task produced a negative skew for the 80% target object size.
Westwood et al. (2001) represents the only study we are aware of providing a tabular summary of mean peak grip aperture values as a function of object size for open-loop manual estimation and grasping. These data revealed that PGA for manual estimation and grasping were 1.10 and 1.56 times larger than the physical size of target objects.
The present work as well as previous open-loop grasping studies by our group (Holmes and Heath 2013; Holmes et al. 2011) employed a movement time (MT) criterion of 600–800 ms. As a result, MTs did not reliably vary as a function of target object size. Bruno et al. (2016) do not report MT values and it is therefore unclear whether target object size influenced the overall timing of grasping.
References
Baranski JV, Petrusic WM (1992) The discriminability of remembered magnitudes. Mem Cogn 20:254–270
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
Bryden MP (1977) Measuring handedness with questionnaires. Neuropsychologia 15:617–624
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, Heath M (2017) The spatial relations between stimulus and response determine an absolute visuo-haptic calibration in pantomime-grasping. Brain Cogn 114:29–39
Davarpanah Jazi S, Hosang S, Heath M (2015) Memory delay and haptic feedback influence the dissociation of tactile cues for perception and action. Neuropsychologia 71:91–100
Dietze AG (1961) Kinaesthetic discrimination: the difference limen for finger span. J Psychol 51:165–168
Franz VH (2003) Manual size estimation: a neuropsychological measure of perception? Exp Brain Res 151:471–477
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
Ganel T, Freud E, Chajut E, Algom D (2012) Accurate visuomotor control below the perceptual threshold of size discrimination. PLoS One 7:e36253
Goodale MA, Milner AD (1992) Separate visual pathways for perception and action. Trends Neurosci 15:20–25
Greiner TM (1991) Hand anthropometry of US army personnel. United States Army Natick Research, Development and Engineering Center. Natick, MA
Heath M, Manzone J (2017) Manual estimations of functionally graspable target objects adhere to Weber’s Law. Exp Brain Res 235:1701–1707
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. doi:10.3389/fnhum.2012.00332
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. Vis 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
Jeannerod M, Arbib MA, Rizzolatti G, Sakata H (1995) Grasping objects: the cortical mechanisms of visuomotor transformation. Trends Neurosci 18:314–320
Johansson RS, Cole KJ (1992) Sensory-motor coordination during grasping and manipulative actions. Curr Opin Neurobiol 2:815–823
Laming D (1986) Sensory analysis. Academic Press, London
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. Academic Press, San Diego, pp 81–178
McKee SP, Welch L (1992) The precision of size constancy. Atten Percept Psychophys 32:1447–1460
Pedhazur EJ (1997) Multiple regression in behavioral research: explanation and prediction. Harcourt Brace College Publishers, Orlando
Pettypiece CE, Goodale MA, Culham JC (2010) Integration of haptic and visual size cues in perception and action revealed through cross-modal conflict. Exp Brain Res 201:863–873
Pheasant ST (1986) Bodyspace: anthropometric ergonomics and design. Taylor and Francis, London
Rossetti Y, Revol P, McIntosh R, Pisella L, Rode G, Danckert J, Tilikete C, Dijkerman HC, Boisson D, Vighetto A, Michel F, Milner AD (2005) Visually guided reaching: bilateral posterior parietal lesions cause a switch from fast visuomotor to slow cognitive control. Neuropsychologia 43:162–177
Smeets JB, Brenner E (1999) A new view on grasping. Mot Control 3:237–271
Smeets JB, Brenner E (2008) Grasping Weber's law. Curr Biol 18:R1089–R1090
Stevens SS, Stone G (1959) Finger span: ratio scale, category scale, and JND scale. J Exp Psychol 57:91
Utz KS, Hesse C, Aschenneller N, Schenk T (2015) Biomechanical factors may explain why grasping violates Weber’s law. Vis Res 111:22–30
Westwood DA, McEachern T, Roy EA (2001) Delayed grasping of a Müller-Lyer figure. Exp Brain Res 141:166–173
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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., Khan, M. et al. Vision for action and perception elicit dissociable adherence to Weber’s law across a range of ‘graspable’ target objects. Exp Brain Res 235, 3003–3012 (2017). https://doi.org/10.1007/s00221-017-5025-1
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DOI: https://doi.org/10.1007/s00221-017-5025-1