The efficiency of multi-generation selection on maternal traits, with implications for reindeer

Maternally affected traits, such as juvenile growth and survival, provide resilience in mammal species, in particular for reindeer living in extreme northern habitat. The genetic variation in such traits is caused by direct and maternal genetic effects (DGE and MGE, respectively). We used Willham’s variance-component approach and extended a family index with the focal individual and its full- and half-sibs to an approximated BLUP (pseudo-BLUP) by including the parents’ estimated breeding values. Most of the deviations of the predicted responses from the simulated ones were 4.1% for DGE and 5.3% for MGE. The benefits of index and BLUP selection are high in the case of negative correlation, large full-sib family and in particular, when maternal half-sibs are available. Higher economic value for MGE than for DGE is needed, since with equal heritabilities and economic weights for the effects the maternal response is 40 to 70% of the direct one. With negative correlation, records on collateral relatives beyond sibs are possibly needed. They would support also the prediction of MGE in uniparous reindeer lacking full-sib information.

What Mothers Do After Infants Vocalize: Implications for Vocal Development or Word Learning?

Purpose The goal of this study was to analyze verbal and nonverbal maternal response types following infant vocalizations in younger (ages 4–8 months) versus older (ages 10–14 months) infant groups and their potential implications for infant vocal development or word learning. Method Maternal response types that occurred within 3 s of infant vocalizations were examined in this cross-sectional study of naturalistic interactions in 35 mother–infant dyads. Response types were defined as vocally responsive to infant vocalizations (i.e., responsive vocal behaviors), not responsive to infant vocalizations directly (nonresponsive vocal behaviors), and silences. Mothers' nonverbal actions associated with each response type were also examined. Subcategories of these verbal and nonverbal response types were examined in relation to infant age group. Results The occurrence of responsive and nonresponsive verbal subcategory types differed by infant age group. When verbally responsive to infant vocalizations, mothers commented on younger infants' vowel and consonant–vowel vocalizations, but with older infants, mothers identified or named the referents of their vocalizations. When nonresponsive to vocalizations directly, mothers commented on younger infants' activities but redirected older infants' behaviors or commented on their movements. Silence after infant vocalizations was infrequent. Mothers' nonverbal actions associated with each response type were primarily object related and did not differ by age group. Conclusions Evaluating response type subcategories by age group indicated mothers did not respond differentially (verbally or nonverbally) to vowel or consonant–vowel vocalizations. Overall, the results suggest mothers' verbal and nonverbal response types may be more likely to facilitate word learning than vocal development.