Verbal reaction times based on tracking lip movement

Valid and reliable measurements of response latency are crucial in testing empirical predictions across fields of psychology. In research utilizing verbal responses, acoustic latency is the typical measure of response latency, but its validity has been questioned. We describe a simple and affordable alternative – articulatory latency based on tracking lip position. Using this method, we measured the acoustic and articulatory latencies of syllables beginning with various simple and complex onsets and ending with “uh” using the speeded naming task, where participants were instructed to have their mouths either closed or open before articulating. The initial oral configuration, place of articulation, and voicing all had significant effects on this measure of articulatory latency across segments, factors that researchers must consider in designing experiments and selecting stimuli.