Sugar and Space? Not the Case: Effects of Low Blood Glucose on Slant Estimation are Mediated by Beliefs

Abstract

There is a current debate concerning whether people's physiological or behavioral potential alters their perception of slanted surfaces. One way to directly test this is to physiologically change people's potential by lowering their blood sugar and comparing their estimates of slant to those with normal blood sugar. In the first investigation of this (Schnall, Zadra, & Proffitt, 2010), it was shown that people with low blood sugar gave higher estimates of slanted surfaces than people with normal blood sugar. The question that arises is whether these higher estimates are due to lower blood sugar, per se, or experimental demand created by other aspects of the experiment. Here evidence was collected from 120 observers showing that directly manipulating physiological potential, while controlling for experimental demand effects, does not alter the perception of slant. Indeed, when experimental demand went against behavioral potential, it produced judgmental biases opposite to those predicted by behavioral potential in the low blood sugar condition. It is suggested that low blood sugar only affects slant judgments by making participants more susceptible to judgmental biases.

Action potential influences spatial perception: Evidence for genuine top-down effects on perception

“…The most frequent challenge to action-specific effects has been the claim that they are due to demand characteristics or response bias (Durgin et al, 2009;Durgin, Klein, Spiegel, Strawser, & Williams, 2012;Shaffer, McManama, Swank, & Durgin, 2013). According to this claim, participants do not literally see the ball as moving faster when the paddle is small, but rather see the ball's speed similarly across paddle sizes.…”

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

“…We have shown that a remote haptic perception response measure overestimates a slanted surface at all orientations from 5°to 54°, much as verbal estimates have been shown to overestimate slanted surfaces across numerous studies (Bhalla & Proffitt, 1999;Bridgeman & Hoover, 2008;Proffitt et al, 1995;Shaffer et al, 2013;Shaffer, McManama, Swank, Williams, & Durgin, 2014). Unlike previous work in which matching tasks have been used to approximate the orientation of slanted surfaces, in the present methodology we used a remote haptic task that allowed for exploration of the entire surface and did not have the restrictions of some of the previous methods (e.g., Bhalla & Proffitt, 1999;Proffitt et al, 1995).…”

“…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;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).…”

“…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 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;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 , 2012.…”