“…First, whilst the experimenter lacked of a history of reinforcement with the participants, the latter's responding could be acquired and maintained by naturally occurring contingencies of reinforcement (e.g., Gena & Kymissis, 2001;Kohler & Greenwood, 1986). That is, the video display might have altered the reinforcing effectiveness of the toy/objects as an example of an establishing operation (Nikopoulos & Keenan, 2004a) which was evidenced by the fact that extinction did not occur in any of the generalization situations (e.g., Koegel, Camarata, Valdez-Menchaca, & Koegel, 1998). Second, a history of reinforcement for imitative responding might exist for these participants by the social community prior to the current study (Masia & Chase, 1997), providing an instance of generalized imitation (e.g., Baer & Deguchi, 1985;Young, Krantz, McClannahan, & Poulson, This article is a version after peer-review, with revisions having been made (i.e., pre-publication version).…”