Lois Bloom and Joanne Bitetti Capatides studied language acquisition in infants: “the relation between infant affect expression and the emergence of language was studied in 6 girls and 6 boys, from 9 months to 2 years of age” (1513). Their interest was in the infants' transition from pre-speech vocalizing to the emergence of language. While some expressions of affect (emotions) are present from birth, forms of speech have to be learned. The researchers wanted to learn if—and if so, how—the expression of emotion might be expected to facilitate learning words. The theory that they tested is based in the “reflectivity hypothesis,” positing that “the time spent in neutral affect states would be associated with early achievements in learning words” (1514).
Their research led them to focus on the neutral affect states and the quiet alert states that previous researchers had examined. Their findings, summarized on p. 1519, led them to see both as relevant to the emotions category of "interest," which others had considered a source of energy in the creation of new cognitive structures and as an organizer and motivator of attention. Their research confirmed for them that neutral affect is important for language learning, as neutral affect expression, as defined in their study, included expression of the emotional category of interest. They suggest that interest is part, but not all, of what was coded in their study as neutral affect, confirming earlier scholars’ views that interest is not a discrete emotion.
Neutral affect, as their study observed it, had antecedents in the quiet alert states of early infancy, but it did not correlate evenly with later ages. As a possible explanation for this, the researchers suggested
that learning to say words may have a stabilizing effect on emotional expression. Given that affective communication is in place from early infancy, learning language entails a shift in attentional resources. Change in one domain (i.e., language) may require stability in another (i.e., emotionality),
referencing Bloom and Wikstrom’s 1987 paper, “The role of temperament in language development.”
Their findings support the idea that children who express emotion frequently are likely to talk later, while those who spend relatively more time in neutral affect are likely to talk earlier.
Bloom, Lois, and Joanne Bitetti Capatides. 1987. “Expression of Affect and the Emergence of Language.” Child Development, Vol. 58, No. 6 (Dec., 1987), pp. 1513-1522