Anchoring in action: Manual estimates of slant are powerfully biased toward initial hand orientation and are correlated with verbal report.

Abstract

People verbally overestimate hill slant by ~15–25° whereas manual estimates (e.g., palm board measures) are thought to be more accurate. The relative accuracy of palm boards has contributed to the widely cited theoretical claim that they tap into an accurate, but unconscious motor representation of locomotor space. In the current work, four replications (total N = 204) carried out by two different laboratories tested an alternative, anchoring hypothesis that manual action measures give low estimates because they are always initiated from horizontal. The results of all four replications indicate that the bias from response anchoring can entirely account for the difference between manual and verbal estimates. Moreover consistent correlations between manual and verbal estimates given by the same observers support the conclusion that both measures are based on the same visual representation. Concepts from the study of judgment under uncertainty apply even to action measures in information rich environments.

Pitching people with an inversion table: Estimates of body orientation are tipped as much as those of visual surfaces

“…Second, they were giving estimates of, say, 15°backward when they were either erect (straight up and down) or oriented at 30°backward (depending on whether they were in the forward or backward sequence). Separate analyses were not reported for forward and backward sequences, so it is not known whether there were anchoring biases that could strongly affect their estimates and whether these were symmetrical or not (Shaffer, McManama, Swank, Williams, & Durgin, 2014;Shaffer, McManama, & Durgin, in press). …”

Palm board and verbal estimates of slant reflect the same perceptual representation

“…Here, we would expect that when people are verbally given an angle of 45°t o reproduce using an adjustable surface, they should stop at 30°, because a surface that is inclined at 30°looks as if it is inclined at 45°. Additionally, if all measures of slant reflect one underlying representation of slant overestimation, and if this is the reason people stop short of the desired angle in the classic palm board task, then if we ask people to estimate at what angle their unseen hand is oriented when it is placed at different angles, we would expect people to overestimate where their hand is oriented by a factor of~1.5, similar to what is found when people estimate inclined surfaces via verbal estimation (Bhalla & Proffitt, 1999;Creem-Regehr et al, 2004;Durgin, Hajnal, et al, 2010, Durgin, Li, et al, 2010Hajnal et al, 2011;Li & Durgin, 2010;Proffitt et al, 1995;Shaffer & Flint, 2011;Shaffer et al, 2014), visual matching (Bhalla & Proffitt, 1999;Proffitt et al, 1995), pedal perception (Hajnal et al 2011), haptic perception (Durgin, Li, et al, 2010), remote haptic perception (2015), downward gaze (Li & Durgin, 2009), and body proprioception (Shaffer, Taylor et al, 2015). So, as we see it, we have described two types of estimation tasks above-verbal estimation and reproduction-and two types of surfacespalm boards and hills/ramps.…”

“…For the last two decades, people have verbally overestimated the slant of visually perceived geographical, virtual, and manmade hills by between 5°and 25° (Bhalla & Proffitt, 1999;Creem-Regehr, Gooch, Sahm, & Thompson, 2004;Durgin, Hajnal, Li, Tonge, & Stigliani, 2010;Hajnal, Abdul-Malak, & Durgin, 2011;Li & Durgin, 2010;Proffitt, Bhalla, Gossweiler, & Midgett, 1995;Shaffer & Flint, 2011;Shaffer, McManama, Swank, Williams, & Durgin, 2014;Stigliani, Li, & Durgin, 2013). Two additional measures have also been used in several of these studies.…”

“…The ideas that palm boards are accurate, are action measures, are reliable, and do not overestimate the true inclination of slanted surfaces has recently been brought into question by work highlighting wrist flexion and anchoring issues with palm boards (Durgin, Hajnal et al, 2010, Durgin, Li et al, 2010Shaffer, McManama, & Durgin, 2015;Shaffer et al, 2014). For instance, it has been shown that palm boards provide biased and insensitive measures that are a reflection of the lack of wrist flexion when using them, and not measures that tap into a distinct visual representation of slant (Durgin, Hajnal et al, 2010, Durgin, Li et al, 2010.…”

“…In these studies, haptic matching estimates are often made using a palm board-people rest their hand on the palm board and rotate it up from horizontal to match the palm board to their visual perception of the slope of the hill (e.g., Bhalla & Proffitt, 1999;Proffitt et al, 1995;Taylor-Covill & Eves, 2013). Some of these studies have also used a free-hand measure for their haptic matching task (Bridgeman & Hoover, 2008;Durgin, Hajnal, et al, 2010, Durgin, Li, et al, 2010Shaffer et al, 2014). This consists of holding one's unseen hand and/or forearm parallel to the slope.…”