Voluntary control of frame of reference and slope equivalence under head rotation.

Transfer studies show that people normally associate responses with physical rather than retinal stimulus orientations. In this study experimental 6"s were instructed to adopt a head-anchored reference system ("Think of the top of your head as 'up'.") with heads tilted, during either initial learning or transfer. These instructions strongly facilitated transfer based on retinal invariance with head position changed. Moreover, faster response to retinal verticals and horizontals than to retinal diagonals with head tilted, prior to transfer, was significantly predictive of superior performance on the transfer task, which required same response to same retinal stimulus with head upright. Conclusions: (o) Invariance of perceived or phenomenal slant (rather than either physical or retinal slant) is the critical determinant of transfer. (&) Likewise, lines perceived as vertical and horizontal tend to evoke faster responses than those perceived as obliques, (c) Phenomenal slant depends on the orientation of a frame of reference, which is subject to voluntary as well as proprioceptive control.