A study is described in which the acquisition of "in,""on," and "under" was studied controlling for the non-linguistic strategies suggested by Clark's (1974) ordered rules, as well as controlling for stimuli bias. Clark's rules were: (1) If Y is a container, put X "in" it; and if Y is not a container, but has a horizontal surface, put X "on" it. This leaves "under" as a last resort. Both neutral and natural toys were used for the present experiment. The nonverbal matching tasks were completed first with the neutral toys, followed by the natural toys. A comprehension task was done first with the neutral toys, then with the natural toys. The subjects were 30 children--16 boys and 14 girls--ranging in age from 22 to 36 months. Results indicate among other things that non-linguistic strategies are a factor regardless of stimuli; 82% of errors on the neutral toys were predicted by Clark's rules. This is taken as an indication that cognitive rules dominate. In addition to Clark's ordered rules, it had also been hypothesized that the specific stimuli used to asses these locative words was a factor. The results of this study support this latter hypothesis as well. The control of cognitive strategy is not sufficient in itself to assure a correct response. The stimuli used for a specific assessment are critical. By changing the stimuli one can increase or decrease the probability of a correct response. (AMH)