One of the standard physiological signals in PDD testing. Respiratory data are generally obtained via a pneumograph transducer placed around the thorax and abdomen of the test subject. PDD examiners historically evaluated breathing movement data through a subjective approach that relied on the presence or absence of various signature patterns indicative of deception. Since breathing is more readily controlled than other activity recorded with the polygraph, it is one of the first areas examiners look for indications of countermeasures. Such indications are paced breathing, holding one’s breath, very slow breathing, irregularly shaped waveforms, hyperventilation, and tactical use of deep breaths. In physiology, respiration refers to the movement of gases across membranes in the lungs, while ventilation is the term used for the expansion and compression of the chest during breathing. See Handler, Reicherter, Nelson, & Fausett (2009).