Researchers use a number of techniques to determine how infants respond to changes in their environment. A. Data from observational methods must be confirmed through multiple studies. B. New techniques for studying infant perception have improved the accuracy with which researchers observe and quantify infant responses C. Indirect observation is most accurate when researchers use it to test auditory and olfactory perception in neonates. D. Visual indicators such as turning the head, blinking the eyes, or crying remain the best evidence of an infant's perceptual abilities. E. Pacifiers are commonly used in studies to calm an infant who has been presented with excessive stimuli. F. Sophisticated techniques that have aided new discoveries about perception in the neonate continue to be indirect measures.