Remote haptic perception of slanted surfaces shows the same scale expansion as visual perception

Atten Percept Psychophys (2015) 77:948–952 DOI 10.3758/s13414-014-0814-0 Remote haptic perception of slanted surfaces shows the same scale expansion as visual perception Dennis M. Shaffer & Eric McManama Published online: 17 December 2014 # The Psychonomic Society, Inc. 2014 Abstract Previous work has shown that overestimates of geographic slant depend on the modality used (verbal or haptic). Recently, that line of reasoning has come into question for many reasons, not the least of which is that the typical method used for measuring “action” has been the use of a palm board, which is not well calibrated to any type of action toward slanted surfaces. In the present work, we investigated how a remote haptic task that has been well calibrated to action in previous work is related to verbal overestimates of slanted surfaces that are out of reach. The results show that haptic estimates are perceptually equivalent to the verbal overestimates that have been found in numerous previous studies. This work shows that the haptic perceptual system is scaled in the same way as the visual perceptual system for estimating the orientation of slanted surfaces that are out of reach. Keywords Spatial vision . Visual perception For the last 20 years, people’s estimates of the orientation of slanted surfaces have been measured both verbally and manually (Bhalla & Proffitt, 1999; Bridgeman & Hoover, 2008; Coleman & Durgin, 2013; Creem-Regehr, Gooch, Sahm, & Thompson, 2004; Durgin, Hajnal, Li, Tonge, & Stigliani, 2010; Durgin & Li, 2012; Durgin, Li, & Hajnal, 2010; Feresin & Agostini, 2007; Hajnal, Abdul-Malak, & Durgin, 2011; Li & Durgin, 2011; Proffitt, Bhalla, Gossweiler, & Midgett, 1995; Proffitt, Creem, & Zosh, 2001; Shaffer, McManama, Swank, & Durgin, 2013; Stefanucci, Proffitt, Clore, & Parekh, 2008; Stigliani, Li, & Durgin, 2013; Taylor-Covill & Eves). D. M. Shaffer (*) : E. McManama Department of Psychology, Ohio State University, 1760 University Drive, Mansfield, Ohio 44906, USA e-mail: All of these studies have documented that people verbally overestimate the slant of hills by between 5° and 25°, depending on the angle of the slanted surface (Bhalla & Proffitt, 1999; Creem-Regehr et al., 2004; Proffitt et al., 1995, Proffitt et al., 2001). In many of these studies, manual estimates have been made using a palm board, which people use by resting a hand on the palm board to match their haptic perception of the palm board to their visual perception of the slope of the hill (e.g., Bhalla & Proffitt, 1999; Creem-Regehr et al., 2004; Durgin et al., 2010a, b; Feresin & Agostini, 2007; Proffitt et al., 1995; Proffitt et al., 2001; Stefanucci et al., 2008; Taylor-Covill & Eves, 2013). More recently, an alternative, free-hand, technique has been used in which estimates are made by holding up an unseen forearm and/or hand to match the slope of the hill proprioceptively (e.g., Bridgeman & Hoover, 2008; Durgin et al., 2010a, b; Shaffer et al., 2013; Stigliani et al., 2013). Whereas verbal estimates suggest that hills appear much steeper than their physical inclination, palm board estimates are typically fairly accurate in matching the true inclinations of hills, whereas free-hand estimates tend to lie between the palm board and verbal estimates. The reason for the apparent difference between palm board estimates and verbal estimates has been proposed to be the perception–action distinction between visual awareness and visually guided action (Bhalla & Proffitt, 1999; Creem & Proffitt, 1998; Proffitt et al., 1995). However, although previous work has claimed that the use of palm boards is a task that measures haptic perception (e.g., Bhalla & Proffitt, 1999; Proffitt et al., 1995), both palm board and free-hand measures are perceptualmatching tasks to a distal stimulus more than they are true haptic-perception tasks, which allow the hand to explore the slanted surface itself using proprioception and proprioceptive feedback. One task that has been used for active haptic exploration and the perception of slanted surfaces seems to be ideally Atten Percept Psychophys (2015) 77:948–952 suited for investigating people’s haptic perceptions of slant. This device and experimental setup is a remote haptic device in which the participant holds one end of a wooden dowel (~1–1.5 m in length) while exploring an ~1-m inclined surface (Fitzpatrick, Carello, Schmidt, & Corey, 1994; Malek & Wagman, 2008; Regia-Corte & Wagman, 2008). These studies have investigated the perception of whether a surface affords climbability and standing upright on it (similar to the methodology of Hajnal, Abdul-Malak, & Durgin, 2011, and Kinsella-Shaw, Shaw, & Turvey, 1992) by using both verbal and remote haptic measures. This work has produced at least two important findings for the present work. First, the visual and haptic perceptual measures revealed equivalent responses in the perception of slant. Second, the remote haptic measure was very good at assessing whether a person would be able to stand on or climb a slanted surface. This is strong evidence for the remote haptic perception task being an action-based measure, whereas the palm board and free-hand matching tasks lack evidence for being action-related measures for the exploration of slanted surfaces (Durgin et al., 2010a, b). The first goal of the present experiment was to investigate remote haptic perception of a slanted surface oriented at six different angles and to compare these results to widely recorded verbal overestimates (e.g., Bhalla & Proffitt, 1999; Durgin & Li, 2011; Hecht, Shaffer, Keshavarz, & Flint, 2014; Proffitt et al., 1995; Shaffer & Flint, 2011; Shaffer et al., 2013). The second goal was to test whether the haptic estimates matched a recent model that has been proposed to explain verbal overestimates and has also been shown to fit people’s verbal overestimates of both small artificial surfaces in a laboratory and outdoor hills (Durgin & Li, 2011, 2012). Method Participants A total of 50 participants (29 male, 21 female) took part in this study, with a mean age of 20.4 years (SD = 4.13). Of these, 45 were right-handed. Participants received course credit for their participation. Materials and apparatus We created a wooden ramp by connecting two pieces of wood (1 m × 1 m) with a hinge. We cut six sets of two rods to hold the top portion of the ramp up into one of the six different angles of inclination (5°, 18°, 30°, 42°, 45°, and 54°) used in the experiment. After putting the rods in place, we measured the ramp with a digital angle inclinometer to make sure that the desired angles were achieved. Participants wore occlusion goggles to prevent them from seeing the surface of the ramp or any part of the surrounding 949 Table 1 Correlations between handedness, height, and arm length and the estimates given Handedness Height Arm length 5° 18° 30° 42° 45° 54° .06 –.12 –.08 .07 .21 –.24 –.14 .07 .16 .05 –.18 –.12 .04 .16 .26 .14 –.03 .06 (...truncated)