This study explored infants' immediate and residual responses to holding and rocking, and how these responses relate to previously proposed mechanisms to explain long term benefits found when infants are repeatedly exposed to tactile and vestibular stimulation. This form of stimulation has been proposed to increase infants' ability to control and organize l) their behavioral state, 2) their arousal and autonomic functioning, or 3) that there is no clear relationship between immediate responses and long term benefits. Behavioral state and heart rate were collected on 40 infants who were randomly assigned to either a control group where infants were briefly repositioned twice but otherwise lay undisturbed for 90 minutes or an experimental group where infants were held and rocked for 30 minutes during the middle of a 90-minute observation. Results of analyses showed that, when infants were held and rocked they 1) displayed a lower Heart Rate Mean and Standard Deviation, 2) displayed a lower Mean Heart Rate During Active Sleep, 3) spent less time in a FussCry State, 3) were less likely to cry continuously, and 4) displayed nominally Smoother State Transitions and greater Stability Within States. Following the cessation of the rocking stimulus infants in the Experimental Group l) displayed a lower Mean Heart Rate, 2) displayed a lower Mean Heart Rate while in a Quiet Alert State, 3) were more likely to spend some time in a Quiet Sleep State, and 4) were less likely to cry continuously. In addition, all infants displayed Smoother State Transitions and greater Stability Within States during the first 30 minutes than during the final 30 minutes of the observation. Finally, across the 90-minute observation, the infants who were not rocked spent progressively more time in a Quiet Alert State, whereas infants who were rocked spent less time in a Quiet Alert State. The results were the most consistent with the hypothesis that the mechanism leading to both the immediate and residual effects of the stimulation was an increase in control and organization of infants’ arousal and autonomic functioning. / Ph. D.