Preliminary Data on Cortical and Acoustical Correlates of Voice Training Under Internal vs External Focus of...

Prior research has emphasized the superiority of an external focus of attention for motor learning. According to the Constrained Action Hypothesis, an external focus encourages automaticity by directing attention to movement outcomes, while an internal focus is thought to impair learning by promoting controlled processing directed at biomechanics. However, prior research has largely conflated two attentional constructs: the locus of attention (external vs internal) and the target of attention (movement outcomes vs biomechanics). Therefore, the purpose of this study was to experimentally separate these constructs within the context of a voice learning task.

Sixteen participants ages 18-38 years with no history of voice disorders or voice training, were randomly assigned to either an external or internal focus of attention group. The task was to produce voice as "clearly" as possible, using an external (sound in the room) or an internal (anterior oral vibrations) focus. A cognitive control task was the Tower of Hanoi game (TOH). Dependent variables across baseline, intervention, and retention phases were spectral moments, spectral slope, and formant cluster prominence (FCP), as well as cognitive effort estimated from functional near-infrared spectroscopy (fNIRS).

The external focus group showed significant increases in spectral mean, standard deviation, and FCP over time, while the internal focus group showed declines or stabilization for the same measures. Neurophysiological oxygenation measures were lower during voice tasks than for the TOH, with no group effect.

Findings challenge the notion that an internal focus is inferior for motor learning. When locus of attention (external vs internal) and target (outcomes vs biomechanics) are decoupled, external focus does not consistently outperform internal focus. Rather than magnitude of learning, locus of attention appeared to affect learning content. Participants instructed to focus on oral vibratory sensations aligned spectral output with oral vibratory receptor frequency sensitivities, while those focused on room sound aligned spectral output with auditory receptor frequency sensitivities. An internal focus on movement outcomes was not associated with increased cognitive effort over an external focus. Findings also call into question traditional stage models of motor learning suggesting a fixed progression from controlled to automatic processes earlier vs later in learning.