Two information-processing theories of motor control have been postulated for motor learning.udRule-based learning theory predicts transfer when new, untrained stimuli or behaviors share theudsame set of rules. Instance-based learning theory predicts transfer when new, untrained stimuliudare similar in a specific way to the trained stimuli. The purpose of this study was to provideudinsight into the learning theory operating during nonword acquisition and transfer by evaluatingudreaction times during an old-new judgment task. Nonword stimuli were constructed to biasudfamiliarity judgments by systematically varying two parameters associated with each theory:udphonetic similarity (instance-based) and syllable stress pattern (rule-based).udTwenty-four participants (18-35 years of age) with normal hearing and speech productionudparticipated in a syllable stress training task and an old-new judgment task. During training,udparticipants articulated a series of nonword stimuli while producing a specific syllable stress pattern. Syllable stress accuracy was monitored by the examiner via perceptual judgments andudcustom software evaluating acoustic intensity of the articulated stressed syllable. Accurateudarticulation of nonwords was monitored with recognition probes throughout training. Participants met pre-established accuracy criteria for syllable stress and phonetic production of eachudexperimental nonword. Once criterion was met, participants were assumed to have a highlyaccurateudbaseline memory representation of the trained items that was judged against a variety ofuduntrained transfer stimuli varying in phonetic similarity and syllable stress pattern. Followingudtraining, an old-new judgment task was administered in which participants made familiarityudjudgments upon hearing a trained or untrained nonword; reaction times were collected via audresponse box.udReaction time results indicated participants responded faster to untrained nonwords withuddifferent phonemes than to untrained nonwords with similar phonemes. Syllable stress patternuddid not affect reaction time. These results are consistent with instance-based learning. However,udthe direction of the similarity effect was in the opposite direction as originally predicted for thisudtheory, i.e., positive transfer occurred when stimuli were dissimilar to one another. Future studiesudshould evaluate what parameters need to be manipulated along a similarity index, and how theudvariable of dissimilarity may affect overall transfer patterns.
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