We present a novel automatic procedure to analyze articulatory setting (AS) or basis of articulation using realtime magnetic resonance images (rt-MRI) of the human vocal tract recorded for read and spontaneously spoken speech. We extract relevant frames of inter-speech pauses (ISPs) and rest positions from MRI sequences of read and spontaneous speech and use automatically-extracted features to quantify areas of different regions of the vocal tract as well as the angle of the jaw. Significant differences were found between the ASs adopted for ISPs in read and spontaneous speech, as well as those between ISPs and absolute rest positions. We further contrast differences between ASs adopted when the person is ready to speak as opposed to an absolute rest position.