Variability of input in preposition learning by preschoolers with developmental language disorder and typically-developing language

The purpose of this study was to investigate the role of variability in teaching prepositions to preschoolers with typical development (TD) and developmental language disorder (DLD). Input variability during teaching can enhance learning, but is target dependent. We hypothesized that high variability of objects would improve preposition learning. We also examined other characteristics (e.g. vocabulary skills) of children who responded to treatment. We used a case series design, repeated across children (n = 18) to contrast how preschoolers learned prepositions in conditions that manipulated variability of objects and labels across three treatment sessions. We contrasted a high versus low variability condition for objects and labels for one group of typically-developing (TD) children (n = 6). In other groups (TD, n = 6; DLD, n = 6), we contrasted high versus low object variability only. Visual inspection and descriptive statistics were used to characterize gains. Half (n = 3) of TD participants showed a low variability advantage for the condition that combined object and label variability. In the condition that only contrasted object variability, the majority (n = 4) of TD participants showed a high variability advantage, compared to only two participants with DLD. In the high object variability condition, high receptive vocabulary scores were significantly correlated with high performance of learning prepositions (r(s) = 0.71, p < 0.05). Combining high variability for objects and labels when teaching prepositions was not effective. However, high variability for objects can create a learning advantage for learning prepositions for children with typically developing language, but not all learners. Characteristics of different learners (e.g. receptive vocabulary scores) and language status (impaired or unimpaired) should be taken into consideration for future studies.