“…Almost 20 years ago, Johnston (1985) proposed that young organisms learn within a developmental system comprising both external influences (e.g., stimuli present within an ecological niche) and internal influences (e.g., status of sensory system development, physiological organization, and experiential history of organism). Previous empirical studies using this systems approach have explored the processes by which young birds (Gottlieb, Tomlinson, & Radell, 1989; Lickliter & Hellewell, 1992; Sleigh, Columbus, & Lickliter, 1996) and mammals (DeCasper & Spence, 1986; Lariviere & Spear, 1996; Mateo, 1996; Poeggel & Braun, 1996; Smotherman & Robinson, 1985; Tees, Buhrmann, & Hanley, 1990) learn to recognize and discriminate between sensory stimuli during early development. Collectively, results from these studies provide strong evidence that early discrimination ability becomes canalized through continuous transactions between the organism's environment and its species-typical biological development.…”