The use of the subliminal implicit learning paradigm in voice motor learning

Abstract

BACKGROUND: Implicit motor learning is referred to the passive accumulation of task-relevant knowledge at an unconscious level. Subliminal learning, a form of implicit learning, utilizes unconscious thresholds to influence behavior in a way that subjects are unaware of the subliminal adaptation in response to the stimuli presented. A Just Noticeable Difference (JND) is the smallest detectable threshold that an individual can detect between two sensory stimuli at above chance level. In order to set up the condition for subliminal learning, it is necessary to first identify the JND in visual stimuli. AIM: The aims of this study were to examine the JND of visual stimuli. METHODS: The JND of 30 subjects (mean age=25.11years) were identified by means of a visual discrimination task of subtle differences between multiple visual stimuli. Visual stimuli were presented in a graph form (two lines at the X and Y-axis) and the changing visual stimulus represented as a line in the middle. Subjects were asked to indicate accurately as possible whether the position of the middle line had changed or not indicating ‘higher’ or lower’ for each trial. RESULTS: Results revealed that subjects were unable to discriminate small subtle differences when the visual stimuli (middle line) changed within 1% visual displacement compared to a standard height, but they were able to discriminate visual changes when the visual stimulus increased above 1.5% displacement(equivalent to 4.5cm differences) of the standard height. When presented with large alteration of the visual stimuli they presented higher level of confidence, suggesting a certainty in their identification of the transforming stimuli. Results from this study provides us with the JND value for setting up further experimental studies on subliminal implicit learning for voice motor learning.