Welcome to the weird world of weight illusions

Normally bigger objects weigh more; breaking this rule provokes illusory perceptionsVisual illusions are useful to psychologists because, by tricking the brain, they provide clues about how it works. The same is true for weight illusions, it's just that they're far less well known. Now Gavin Buckingham at Heriot-Watt University has published a handy review of weight illusions, and he explores some of the thinking about their likely causes.Among the most studied is known as the "size-weight illusion (SWI)". When a person is presented with two objects - one large, one small - that weigh the same, the smaller object feels heavier. The illusion persists even when the perceiver is told what's going on.One explanation for the SWI is that, anticipating it will be heavier, we use stronger force to lift the bigger object than the smaller one. The greater force used to lift the bigger object leads to the perception of lightness, so the argument goes. But this explanation can't account for the fact that the illusion persists regardless of how many times we perform the lifts, and as we adjust our anticipatory force.Although the SWI illusion persists through repeated liftings, it can actually be reversed through extensive training. Buckingham describes a study in which groups of participants were repeatedly exposed to sets of "inverted-density" objects, in which it was always the smaller items that were heavier. One session of 1000 such lifts reduced the SWI slightly. Three days, conducti...
Source: BPS RESEARCH DIGEST - Category: Psychiatrists and Psychologists Authors: Source Type: blogs