TABLE X

	Single Judgment			Two Judgments			Three Judgments
Obs.	Length	Lines	Shade	Length	Lines	Shade	Length	Lines	Shade
A Number of series averaged	11	12	10	15	17	14	11	11	11
Per cent Correct Judgments	95	93	96	90	91	83	94	91	89
	\———\/———/			\———\/———/			\———\/———/
Average	95			88			91
B Number of series averaged	8	8	7	9	10	9	7	7	7
Per cent Correct Judgments	93	80	90	76	77	90	75	70	75
	\———\/———/			\———\/———/			\———\/———/
Average	88			81			73
Y Number of series averaged	12	13	13	19	19	16	13	13	13
Per cent Correct Judgments	76	80	58	72	76	61	72	74	58
	\———\/———/			\———\/———/			\———\/———/
Average	71			70			68

Since these general averages for the single judgments are so close to those in pairs, it seemed possible that the presence of objective differences, other than the single one asked for, might be a distracting agent, and really interfere with the judgment process in question. For example, when judgment on length was in question, it might be possible to give it correctly a larger number of times, if there were no differences in shade or lines, than if these were present. Some careful test experiments were made with a view to clearing up this situation. The observers in no case knew the nature of the investigation, nor were they aware that other differences were absent in some of the cases. The results presented in Table XI certainly show that the presence of other differences than the one in question is no cause of interference.