may follow a relatively protracted
developmental course. We examined whether infants know such abstract words.
Parents named one of two events shown in side-by-side videos while their 6–16-monthold
infants (n = 98) watched. On average, infants successfully looked at the named video
by 10 months, but not earlier, and infants’ looking at the named referent increased robustly
at around 14 months. Six-month-olds already understand concrete words in this task
(Bergelson & Swingley, 2012). A video-corpus analysis of unscripted mother-infant interaction
showed that mothers used the tested abstract words less often in the presence of their
referent events than they used concrete words in the presence of their referent objects. We
suggest that referential uncertainty in abstract words’ teaching conditions may explain the
later acquisition of abstract than concrete words, and we discuss the possible role of
changes in social-cognitive abilities over the 6–14 month period.