As I have argued (Marcus, 2001; Marcus, 1998; Marcus, Vijayan, Bandi Rao, & Vishton, 
1999; Berent, Marcus, Shimron, & Gafos, 2002; Berent, Vaknin, & Marcus, 2007) symbol-
manipulation in some form seems to be essential for human cognition, such as when a 
child learns an abstract linguistic pattern, or the meaning of a term like sister  that can be 
applied in an infinite number of families, or when an adult extends a familiar linguistic 
pattern in a novel way that extends beyond a training distributions (Berent et al., 2002; 
Berent et al., 2007).  Some of the most compelling evidence for this came from a 1999 
study (Marcus et al., 1999) in which my colleagues and I showed that 7-month old 
infants could recognize simple abstract patterns such as the ABB pattern in la ta ta and 
extrapolate them beyond a set of training examples to novel strings composed entirely 
of different syllables that didn't phonetically overlap with their training set. Subsequent
The Next Decade in AI-