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Fig. 6. Geometry of test space and outward journeys in experiment II. The nest box
is located under the arena floor, the nest exit (diameter, 9 cm) being located
at a distance of 50 cm from the arena wall. The hamster can easily climb from
the underground nest into the arena. Before each test trial, the arena is
rotated by 135°. The outward journey (continuous line with heavy arrows)
leads from the (rotated) nest exit (N135°) over 60 cm to point P1, and,
with the exception of fix-without-translation trials, over a further
translation of 110 cm to point P2. In baseline trials, the animal proceeds to
P1, where it takes up some food, and then to P2, where it fills its cheek
pouches completely. Baseline-with-circling trials follow the same pattern
except that the subject walks along two full circles near P1 (circle passing
through P1) instead of taking up some food. In fix-without-translation trials,
the animal walks to P1, follows two full circles in the dark, and then a
further circle in the opposite direction under light. Fix-with-translation
trials include an additional translation from point P1 to point P2 after the
fix. During the fix at P1, the nest direction, as established by visual cues
on the one hand and by PI on the other hand, diverge by 
67°. A full
resetting would lead to the standard nest location N0°, and a partial
(direction only) resetting to the virtual nest location NDR. The theoretical
homing directions based on a full or a partial resetting differ by 72° at
P1 and by 125° at P2.
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