Measuring mislocalization of angle vertices.

Localisation of simple stimuli such as angle vertices may contribute to a plethora of illusory effects. We focus on the Müller-Lyer illusion in an attempt to measure and characterise a more elementary effect that may contribute to the magnitude of said illusion. Perceived location error of angle vertices (a single set of Müller-Lyer fins) and arcs in a 2D plane was measured with the aim to provide clarification of ambiguous results from studies of angle localisation and expand the results to other types of stimuli. In three experiments, we utilised the method of constant stimuli in order to determine perceived locations of angle vertices (Experiments 1 and 2) as well as circular and elliptical arcs (Experiment 3). The results show significant distortions of perceived compared to objective vertex locations (all effect sizes d > 1.01, p < .001). Experiment 2 revealed strong effects of angle size and fin length on localisation error. Mislocalization was larger for more acute angles and longer angle fins (both ηp² = .43, p < .001). In Experiment 3, localisation errors were larger for longer arcs (ηp² = .19, p = .001) irrespective of shape (circular or elliptical). We discuss the effect in the context of modern trends in research of the Müller-Lyer illusion as well as the widely popular centroid theory. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Single-Heuristic Reasoning: Is It Still Dual-Process?

Traditionally, paradigms used to study conflict in reasoning (and metacognition during reasoning) pit heuristic processes against analytical processes. Findings indicate that the presence of conflict between processes prolongs reasoning and decreases accuracy and confidence. In this study, we aimed to explore reasoning and metacognition when only one type of heuristic process is exploited to cue multiple responses. In two experiments, a novel modification of the Base Rate neglect task was used to create versions in which one belief-based heuristic competes, or works in concert, with another of the same type to provide a response. Experiment 1 results reveal that the presence of conflict between cued responses does not affect meta-reasoning, which indicates that reasoning defaulted to a single process. An alternative explanation was that the effect of conflict was masked due to an imbalance in the strength of the dominant response between conflicting and congruent versions. Experiment 2 was designed to test hypotheses based on these competing explanations. Findings show that when the strength of a response was no longer masking the effect, the conflict did result in longer reasoning times and lower confidence. The study provides more robust evidence in favor of the dual-process account of reasoning, introduces a new methodological approach, and discusses how conflict may be modulated during reasoning.

Hierarchical Control of Visually-Guided Movements in a 3D-Printed Robot Arm.

The control architecture guiding simple movements such as reaching toward a visual target remains an open problem. The nervous system needs to integrate different sensory modalities and coordinate multiple degrees of freedom in the human arm to achieve that goal. The challenge increases due to noise and transport delays in neural signals, non-linear and fatigable muscles as actuators, and unpredictable environmental disturbances. Here we examined the capabilities of hierarchical feedback control models proposed by W. T. Powers, so far only tested in silico. We built a robot arm system with four degrees of freedom, including a visual system for locating the planar position of the hand, joint angle proprioception, and pressure sensing in one point of contact. We subjected the robot to various human-inspired reaching and tracking tasks and found features of biological movement, such as isochrony and bell-shaped velocity profiles in straight-line movements, and the speed-curvature power law in curved movements. These behavioral properties emerge without trajectory planning or explicit optimization algorithms. We then applied static structural perturbations to the robot: we blocked the wrist joint, tilted the writing surface, extended the hand with a tool, and rotated the visual system. For all of them, we found that the arm in machina adapts its behavior without being reprogrammed. In sum, while limited in speed and precision (by the nature of the do-it-yourself inexpensive components we used to build the robot from scratch), when faced with the noise, delays, non-linearities, and unpredictable disturbances of the real world, the embodied control architecture shown here balances biological realism with design simplicity.

The snow tire illusion: Different levels of perceptual assimilation across a single stimulus configuration.

While observing a specific traffic sign in the field, we noticed an apparent distortion of size and shape of the circle that contained the sign. This novel illusion manifests as a distortion of the horizontal compared to the vertical dimension of the sign. The illusion seems to be underlined by similar mechanisms to those in the Delboeuf illusion. The aim of our study was to determine the existence and magnitude of the snow tire illusion. We conducted two experiments using the method of constant stimuli. The first experiment was conducted on the standard sign, while in the second, the stimuli were rotated 90° counterclockwise. Both experiments consisted of three conditions: the snow tire, the ellipse, and the simple circle (control) conditions. The data showed a robust illusion effect for both the standard and rotated sign compared to the control condition, with a large majority of participants experiencing the illusion. The snow tire illusion seems to be a combination of assimilation mechanisms of different magnitudes. The assimilation is larger for one dimension of the sign, thus producing the shape distortion. The illusion may be a manifestation of a thus far undocumented non-uniform effect of assimilation on perceived size and shape.