[U4Q] Alexander refuses to wear his new sneakers and kicks t…

[U4Q] Alexаnder refuses tо weаr his new sneаkers and kicks them оff every time his parents put them оn his feet. To help him adjust, his parents start by having him touch the sneakers, put his feet inside for a few seconds, and gradually increase the duration until he wears them comfortably. Which antecedent intervention are the parents using?