“…Harnad (1990) highlighted the challenging nature of the relationship between a word and its meaning, calling it the symbol grounding problem. Words for some physical objects can be grounded in sensorimotor percepts (Vogt, 2002;Steels, 2005;Roy, 2005;Steels, 2008;Schulz et al, 2011aSchulz et al, , 2011b, while other concepts may be grounded in secondary structures (Cangelosi and Riga, 2006;Cangelosi et al, 2010;Schulz et al, 2011aSchulz et al, , 2011bUno et al, 2011).…”