Since Mary Ainsworth's formulation of the Sensitivity-Insensitivity to Infant Signals and Communications observational scale, new instruments have been developed to observe parental sensitivity. In this paper, we provide an overview of eight commonly used observational instruments to measure parental sensitivity. Their similarities and differences in comparison to the original Ainsworth sensitivity construct and its applications will be discussed. Consistent with the search criteria, each of the instruments clearly includes the key elements of Ainsworth's definition of sensitivity. Notable deviations from the original scale are the use of composite scales rather than a single global scale and the related inclusion of new elements, and specifically the inclusion of positive affect as an indicator of sensitivity. Further, most of the instruments have a wider scope than Ainsworth's sensitivity scale in terms of target age groups and the assessment of sensitivity in fathers. We discuss the interpretation of the sensitivity construct depending on variations in how the construct is defined in different observational instruments, and advances in the application of the construct.