Sniffing (behavior)

Sniffing is a perceptually-relevant behavior, defined as the active sampling of odors through the nasal cavity for the purpose of information acquisition. This behavior, displayed by all terrestrial vertebrates, is typically identified based upon changes in respiratory frequency and/or amplitude, and is often studied in the context of odor guided behaviors and olfactory perceptual tasks. Sniffing is quantified by measuring intra-nasal pressure or flow or air or, while less accurate, through a strain gauge on the chest to measure total respiratory volume. Strategies for sniffing behavior vary depending upon the animal, with small animals (rats, mice, hamsters) displaying sniffing frequencies ranging from 4 to 12 Hz but larger animals (humans) sniffing at much lower frequencies, usually less than 2 Hz. Subserving sniffing behaviors, evidence for an ""olfactomotor"" circuit in the brain exists, wherein perception or expectation of an odor can trigger brain respiratory center to allow for the modulation of sniffing frequency and amplitude and thus acquisition of odor information. Sniffing is analogous to other stimulus sampling behaviors, including visual saccades, active touch, and whisker movements in small animals (viz., whisking). Atypical sniffing has been reported in cases of neurological disorders, especially those disorders characterized by impaired motor function and olfactory perception.