Visual inspection of three-dimensional objects by human observers
T. Niemann, M. Lappe & K.-P. Hoffmann
Perception 25:1027-1042, 1996
- Eye movements are an important aid in active visual exploration of the environment and in performing behavioural
tasks. Eye movements might also play a role in human perception of three-dimensional objects. We investigated eye
movement strategies when humans inspected and memorised 3D-objects. Subjects were instructed to memorise the 3D-structure
of parts of statues of human figures placed on a turntable free to rotate through 360_. Eye movements and turning
behaviour were recorded. Different turning and eye movement strategies could be observed. Subjects showed individual
turning behaviours that was reproducible between trials. Turning strategies ranged from focusing on only a limited
number of perspective views to rather continuously rotating the object with only short stops. On average 12-13
views were inspected during memorising. Eye movements also revealed individual strategies. Fixation locations within
each inspection view ranged from either closely spaced on isolated parts of the object to distributed over the
whole view with large saccades in between. Eye movements were often directed to the same details from different
perspectives. The differences in turning and viewing strategy also resulted in differences in the ability recognise
parts of the object later on. In general, successful later recognition required that the subject actually fixated
the part to be recognised. A strategy of thoroughly inspecting the object with a series of closely spaced fixations
from only a limited number of viewpoints leads to best recognition rates. This was especially true for two subjects
trained in fine arts with prior experiences in modelling. The results support models of viewpoint-dependent object
recognition with viewer-centred, 2D-representations of 3D-objects.
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