This study sought to further investigate the effects of an observational intervention for two participants on the reinforcing property of pieces of string. Pre-observational intervention data showed that the neutral stimuli (strings) did not function to reinforce two participants' responding to a performance task or learning three new skills that were not previously in their repertoires. The observational intervention involved the participants observing a peer confederate receive strings following responses that the participants could not see while they were deprived strings, regardless of whether their responses were correct or incorrect. Once the participants met criterion for terminating the intervention the same performance and learning tasks were again presented. The data showed that the strings now functioned to reinforce both performance and learning tasks. The results are discussed in terms of the utility of this procedure as an alternative to traditional stimulus-stimulus pairing procedures for conditioning neutral stimuli as reinforcers. (Contains 3 tables and 5 figures.)