This paper presents two different perspectives on the acquisition of voicing in word-initial stops, in order to determine the patterns that children follow when acquiring
the voicing contrasts of a language. The first contains a discussion based on voice onset time (VOT), the most commonly used method of testing voicing contrasts in speech. According to Macken and Barton (1980), "VOT refers to the time interval between the release of stop closure and the onset of vocal fold vibration." The last perspective is based on the underspecification theory presented from a nonlinear point of view, a more recent approach to phonology that relies heavily on distinctive features, in this case the features [voice] and [spread] under the laryngeal node.This paper will also argue that cross-linguistically the voiceless member of a stop pair is more common than the voiced member, and it is also acquired earlier by children.
The evidence from languages like English, where the voiced member is predominant in both children's and adult output speech, challenges this statement. Therefore I think that it is important to address this statement with respect to the English language.
Onslow, J. (1998). The acquisition of voicing contrasts in word-initial obstruent stops. Calgary Working Papers in Linguistics, 20(Winter), 73-84.