抄録
Eight Japanese monkeys were split into two groups. One experimental, the other control. Both experimental and control SS first received discrimination training with Orange cylinder (+) and Green cylinder (-) using a modified WGTA.
SS in experimental group received so called direct placement i. e., SS themselves could not directly manipulate both stimulus objects, but the experimenter himself opened the positive stimulus object (Orange cylinder) and pulled it toward the experimenter 15 trials and immediately after the operation, ordinal experimental extinction were given. Whereas SS in control group received ordinal extinction.
In the ordinal extinction session, seven colors were employed and the preference of colors were measured in experimental group, but in control group only five colors were employed.
Japanese monkeys might have some preferred colors, but unfortunately they were not well known, and first session all SS had experienced discrimination training, so that it might be necessary to check the innately preferred colors. 50 days after finishing the all experiment, 7 colors were presented on the tray in a raw and the preference of the colors were measured. If the 7 colors equally preferred the probability of choice would resulted in 1/7=14.3 percent respectively.
Main results were as follows :
1) Fig. 2 clearly shown that the previously positive object (Orange colored cylinder) reduced the incentive function by just looking at the empty food well.
2) Previously negative object (Green colored cylinder) reversely increased the percentage of preference.
3) SS in control-2 group have preferred rather equally the 7 colors, and X2-test to the data obtained revealed no significant differences.
Apart from ordinal rg hypothesis a plausible assumption to explain the results was postulated in discussion phase.
