An anti-inertial motion bias explains people discounting inertial motion of carried objects.

In this paper we propose an anti-inertial motion (AIM) bias that can explain several intuitive physics beliefs including the straight-down belief and beliefs held concerning the pendulum problem. We show how the AIM bias also explains two new beliefs that we explore - a straight-up-and-down belief as well as a straight-out/backward bias that occurs for objects traveling in one plane that are then thrown in another plane, ostensibly affording a greater opportunity for perception of canonical motion. We then show how the AIM bias in general is invariant across perceived/imagined speed of the object carrier, only altering percentages of straight-out from backward responses, and why occluding the carrier once the object is released into a second plane does not result in more veridical perception.

Manipulation of expended effort and intent does not affect estimates of slant or distance.

It is well known that people overestimate the orientation of both geographical and man-made sloped surfaces by between 5°-20°. More recently, work has shown that when people are encumbered by wearing a heavy backpack they overestimate hills and distances even more than a group not wearing heavy backpacks; however, the backpack manipulation has since been shown to be a demand effect-that is, being encumbered does not affect perception-it only biases those people influenced by it to give estimates the experimenters are seeking. Here we first show that expended effort and intent have never actually been manipulated between subjects in any of the work on steepness estimates, and expended effort has never been explicitly manipulated between subjects for distance estimates.

Pedal and haptic estimates of slant suggest a common underlying representation.

It is well known that people verbally exaggerate the slant of visually perceived geographical, virtual, and man-made hills. More recently it has been shown that haptic and verbal estimates of slant result in similar exaggerations, supporting the proprioception calibration hypothesis-that similar biases exist in both verbal estimates of visually perceived slant and proprioceptively perceived hand orientation. This seems to point to a common underlying representation of slant.

Pushing people to their tipping point: Phenomenal tipping point is predicted by phenomenal vertical and intuitive beliefs.

Previous work has shown that people overestimate their own body tilt by a factor of about 1.5, the same factor by which people overestimate geographical and man-made slopes. In Experiment 1 we investigated whether people can accurately identify their own and others' tipping points (TPs) - the point at which they are tilted backward and would no longer be able to return to upright - as well as their own and others' center of mass (COM) - the relative position of which is used to determine actual TP.

Perception of objects oriented downward from a vertical position.

In the present work we investigated people's perceptions of orientation for surfaces that are conceived of as being sloped downward from vertical against a vertical reference frame. In the three conditions of Experiment 1, participants either (1) placed a ladder against a wall at what they thought was the most stable position, and then estimated its orientation; (2) gave a verbal (conceptual) estimate of what the most stable position of a ladder leaned against a wall would be; or (3) drew a line representing the most stable position of a ladder to be placed against a wall, and then gave a verbal estimate of the ladder's orientation. Ladder placement was shallower than the most stable position, as were the verbal estimations of both the positioned and drawn orientations and the verbal (conceptual) estimates of the most stable position for a ladder to be leaned against a wall, relative to the actual orientations.

The geometry of consciousness.

Conscious experience implies a reference-frame or vantage, which is often important in scientific models. Control models of ball-interception are used as an example. Models that use viewer-dependent egocentric reference-frames are contrasted with viewer-independent allocentric ones.

The power law as behavioral illusion: reappraising the reappraisals.

Marken and Shaffer (Exp Brain Res 235:1835-1842, 2017) have argued that the power law of movement, which is generally thought to reflect the mechanisms that produce movement, is actually an example of what Powers (Psychol Rev 85:417-435, 1978) dubbed a behavioral illusion, where an observed relationship between variables is seen as revealing something about the mechanisms that produce a behavior when, in fact, it does not. Zago et al. (Exp Brain Res.

The power law of movement: an example of a behavioral illusion.

The curved movements produced by living organisms follow a power law where the velocity of movement is a power function of the degree of curvature through which the movement is made. The exponent of the power function is close to either 1/3 or 2/3 depending on how velocity and curvature are measured. This power law is thought to reflect biological and/or kinematic constraints on how organisms produce movements.

Free hand proprioception is well calibrated to verbal estimates of slanted surfaces.

We investigate the relationship between verbal and hand proprioception of slant. In Experiment 1 we demonstrate that verbally estimating free hand orientation produces overestimates by a factor of 1.67.

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

People verbally overestimate the orientation of slanted surfaces, but accurately estimate or underestimate slanted surfaces using a palm board. We demonstrate a fundamental issue that explains why the two different values typically given for palm board and verbal/visual matching estimates express similar perceptual representations of slanted surfaces. The fundamental problem in studies measuring palm board and verbal estimates is that the "measure"-either (1) reproducing a verbally given angle or the orientation of a slanted surface with an unseen hand or (2) verbally or visually estimating a visually perceived surface-has always been confounded with the "surface"-either using (1) a palm board or (2) a hill or ramp.

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

In the current work we investigate people's perception of their own body tilt in the pitch direction. In Experiment 1, we tilted people backward at 1 of 5 different randomly assigned angles using an inversion table. People significantly overestimated the angle at which they were tilted backward at angles from 8° to 45°.

Catching objects thrown to oneself: Testing control strategies for object interception in a novel domain.

A considerable amount of research has been performed to determine the strategies people use to intercept moving objects. Much of this research has been done using target objects such as baseballs and Frisbees that are launched to people from distances ranging from 10 m to 50 m. This research has qualified the range of domains in which each strategy is effective, but there is still controversy regarding which strategy has the most general application.

Manual anchoring biases in slant estimation affect matches even for near surfaces.

People verbally overestimate hill slant by ~15°-25°, whereas manual estimates (e.g., palm board measures) are thought to be more accurate.

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

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.

Slope estimation and viewing distance of the observer.

The overestimation of geographical slant is one of the most sizable visual illusions. However, in some cases estimates of close-by slopes within the range of the observer's personal space have been found to be rather accurate. We propose that the seemingly diverse findings can be reconciled when taking the viewing distance of the observer into account.

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

People verbally overestimate hill slant by approximately 15° to 25°, whereas manual estimates (e.g., palm board measures) are thought to be more accurate.

Receivers in American football use a constant optical projection plane angle to pursue and catch thrown footballs.

In the present work we test how well two interceptive strategies, which have been proposed for catching balls hit high in the air in baseball and cricket, account for receivers in American football catching footballs. This is an important test of the domain generality of these strategies as this is the first study examining a situation where the pursuer's locomotor axis is directed away from the origin of the ball, and because the flight characteristics of an American football are far different from targets studied in prior work. The first strategy is to elicit changes in the ball's lateral optical position that match changes in the vertical optical position so that the optical projection plane angle, psi, remains constant, thus resulting in a linear optical trajectory (LOT).

Chasin' choppers: using unpredictable trajectories to test theories of object interception.

Three theories of the informational basis for object interception strategies were tested in an experiment where participants pursued toy helicopters. Helicopters were used as targets because their unpredictable trajectories have different effects on the optical variables that have been proposed as the basis of object interception, providing a basis for determining the variables that best explain this behavior. Participants pursued helicopters while the positions of both pursuer and helicopter were continuously monitored.

Sugar and space? Not the case: Effects of low blood glucose on slant estimation are mediated by beliefs.

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.

Blind(fold)ed by science: a constant target-heading angle is used in visual and nonvisual pursuit.

Previous work investigating the strategies that observers use to intercept moving targets has shown that observers maintain a constant target-heading angle (CTHA) to achieve interception. Most of this work has concluded or indirectly assumed that vision is necessary to do this. We investigated whether blindfolded pursuers chasing a ball carrier holding a beeping football would utilize the same strategy that sighted observers use to chase a ball carrier.

To see or not to see: effects of visual feedback on performance and intuitions of quarterbacks in American football.

We investigated the ability of quarterbacks in American football to intercept a moving receiver with a football in occluded and normal viewing conditions, and whether they can accurately predict their own success. Quarterbacks were successful in almost 80% of the trials in the occlusion condition, statistically as successful as in the normal viewing condition. Quarterbacks' predictions of their own success accounted for little variance in actual success.

The visual perception of lines on the road.

The present work demonstrates that observers grossly underestimate the length of lines parallel to their line of sight. In Experiment 1, observers, working from memory, estimated the length of a dashed line on the road to be 0.61 m.

Evidence for a generic interceptive strategy.

In the present work, we first clarify a more precise definition of instantaneous optical angles in control tasks such as interception. We then test how well two interceptive strategies that have been proposed for catching fly balls account for human Frisbee-catching behavior. The first strategy is to maintain the ball's image along a linear optical trajectory (LOT).

Naive beliefs in baseball: systematic distortion in perceived time of apex for fly balls.

When fielders catch fly balls they use geometric properties to optically maintain control over the ball. The strategy provides ongoing guidance without indicating precise positional information concerning where the ball is located in space. Here, the authors show that observers have striking misconceptions about what the motion of projectiles should look like from various perspectives and that they estimate when the physical apex of a fly ball occurs to be far later than actual, irrespective of baseball experience.