Table 1.

Rules underlying the VWT Test Phases I–III

	Visual water task - rules
Frequency range (cyc/deg)	0.086–0.172	0.201–0.372	≥0.401
Criteria to pass(correct trials/total trials)	1/1	3/3	5/5
	or 3/4	or 5/6	or 7/10
	or 7/10	or 7/10
	→ break	→ break	→ break

Different criteria applied for different spatial frequency ranges, e.g., in the lowest range, one correct trial was sufficient for passing this frequency step, resulting in an increase of the spatial frequency. If an animal failed the first trial, it still had the chance to pass by correctly choosing in three out of four or seven out of 10 trials. If it failed, the spatial frequency was decreased by three steps. In higher frequency ranges, the criteria were more strict to exclude coincidental passing.