Abstract:
Time perception and estimation are very important aspects of human behavior. Whether these are based on a single internal clock or the result of distributed and emergent processes in the brain is still a matter of debate. The present thesis investigated the effects of lateralized presentation of auditory and tactile stimulation to assess whether time estimation is lateralized and affected by stimulus modality. Additionally, performances of both female and male trained musicians were compared to those of non-musicians to evaluate the effects of gender and training in time estimation. In an identical subject design, subjects attended a time duration comparison task for short (100 to 900 milliseconds in 50 milliseconds increments with a standard stimulus of 500 msec) and long ranges (1 to 5 seconds in 250 milliseconds increments with a standard of 3000 msec) in auditory and tactile modalities. Subjects listened to pairs of sounds either monaurally or binaurally and indicated whether the two stimuli were of equal duration. Tactile (vibratory) stimuli were applied on the top of either the right or the left hand. Stimulus pairs were presented in ascending or descending order. The results suggested a gender difference; males were more accurate in time estimation. Gender differences may be due to different corpus callosum sizes between males and females. Findings also suggested that musicians were more accurate except for the short tactile range. Better performance by musicians in both modalities suggests that time estimation in one modality can be generalized to others. Additionally, an analysis of estimation errors compared to the standard durations (percent of error) indicated that overall performance was better in the long range. There was no significant laterality effect except for long range tactile condition. Better overall performances of subjects in estimating the longer standard duration suggest that there may be different timing mechanisms in the brain, such as for long ranges which may include cognitive processes and for short ranges that are more low-level (sensory) and automatic. The present results also provide support for the view that the brain does not have a lateralized internal clock.
