Mass distribution and shape influence the perceived weight of objects.

Research suggests that the rotational dynamics of an object underpins our perception of its weight. We examine the generalisability of that account using a more ecologically valid way of manipulating an object's mass distribution (mass concentrated either at the top, bottom, centre, near the edges or evenly distributed throughout the object), shape (cube or sphere), and lifting approach (lifting directly by the hand or indirectly using a handle or string). The results were in line with our predictions. An interaction effect was found where the mass distribution and lifting approach both associated with the lowest rotational dynamics made the stimulus appear lighter compared to other combinations. These findings demonstrate rotational dynamic effects in a more run-of-the-mill experience of weight perception than what has been demonstrated before using cumbersome stimuli.

The role of line-orientation processing in the production of the Poggendorff illusion: A dual-task study.

Using a dual-task paradigm, the present investigation examined whether processes related to line orientation play a critical role in the production of the Poggendorff illusion. In Experiment 1, we assessed the magnitude of the Poggendorff illusion under three different task conditions. In the single-task condition, participants were asked to report how they perceive the alignment of transversal lines in the Poggendorff figure. In two different dual-task conditions, the participants were asked to read aloud the time displayed on a digital or analogue clock while also performing the Poggendorff perception task. The method of constant stimuli was used to calculate the point of subjective equality (PSE) and bistability width values, which represent illusion strength and perceptual uncertainty, respectively. PSEs indicated that the magnitude of the illusion did not vary between single, dual-analogue, and dual-digital task conditions, which suggests that the additional demands placed by the dual tasks had no effect on the illusion strength. Perceptual uncertainty and clock-reading errors were greater in the dual-analogue task condition. Experiment 2 revealed that the analogue clockface was more difficult to read than the digital clockface. Based on these results, we conclude that having participants perform a secondary task does not influence the magnitude of the Poggendorff illusion.