Cue combination and individual differences during weight judgements using familiar and newly learned cues.

Human perception is often characterised by efficient combination of sensory signals (cues). In recent studies, people could also improve precision via newly learned cues, with applications to enhance perception in healthy and clinical groups. However, it is unclear whether new cues can enhance manual object interactions. To study how new cues are used for object weight perception, people compared weights of containers. With haptic information plus the familiar visual cue of volume, participants showed precision improvements indicating cue combination. By contrast, a group of participants briefly trained with a novel visual cue to weight (line orientation) did not show improvements expected from combination. We then asked whether prolonged training (12 h) with the novel cue would promote combination, testing for significant precision gains individually in six participants. Half of participants showed combination benefits, but these were not clearly related to training, as some combined cues before training. Using an illusion analogous to the size-weight illusion, we also asked whether the novel cue would become an automatic predictor of weight: two participants were susceptible to the illusion. We conclude that weight perception is susceptible to some enhancement, but subject to training effects and individual differences that are not yet understood.