e. Toddlers who use more gesture + speech combinations at 18 months also
demonstrate greater sentence complexity at 42 months of age.
5. Mirror Neurons and Gestures
a. Mirror neurons, a type of visuomotor neurons (related both to vision and to
muscular movement), activate when people perform actions.
C. Theory of Mind
1. One common measure of ToM development is a false-belief task.
3. A meta-analysis demonstrated a significant relation between children’s language and
theory of mind, as measured by false-belief tasks.
5. As toddlers observe a social partner’s actions and reactions to shared objects during
periods of coordinated joint engagement and as they talk about shared objects during
II. What Major Achievements in Language Form, Content, and Use Characterize Toddlerhood?
A. Language Form
1. Achievements in Phonology
a. Toddlers begin to acquire and refine their repertoire of speech sounds, or
phonemes, and as they do so, adults witness their phonological processes or those
arguably cute rule-governed errors children make when pronouncing certain
words.
b. Norms for Phoneme Attainment
• The term customary age of production describes the age by which 50% of
children can produce a given sound in multiple positions in words in an
adultlike way.
c. Phonological Processes
• Children who appear to make errors are in fact using systematic, rule-
governed processes as they speak and are not simply making haphazard sound
substitutions. The systematic, rule-governed patterns that characterize
toddlers’ speech are called phonological processes.