Sequence learning in 4-month-old infants: do infants represent ordinal information?

This study investigated how 4-month-old infants represent sequences: Do they track the statistical relations among specific sequence elements (e.g., AB, BC) or do they encode abstract ordinal positions (i.e., B is second)? Infants were habituated to sequences of 4 moving and sounding elements-3 of the elements varied in their ordinal position while the position of 1 target element remained invariant (e.g., ABCD, CBDA)-and then were tested for the detection of changes in the target's position. Infants detected an ordinal change only when it disrupted the statistical co-occurrence of elements but not when statistical information was controlled. It is concluded that 4-month-olds learn the order of sequence elements by tracking their statistical associations but not their invariant ordinal position.