Parallel Behind Your Head.

A miniature hair clip set-up presented to the first author gave inspiration for this study. After a number of studies investigating what is haptically perceived as parallel on horizontal, frontoparallel or midsagittal planes, the present study focusses on what is felt as parallel behind your head. The results show convincingly that also in this condition physically parallel is not the same as haptically parallel. Moreover, the deviations are large, idiosyncratic and in a direction predicted by assuming a biasing influence of an egocentric reference frame.