Behavioral imprinting is a learning phenomenon by which animals acquire preferences for
stimuli by perceptual exposure during critical periods, without substantial external
reinforcement. Since being acknowledged in 1516 by Sir Thomas More in artificially incubated
domestic chickens, imprinting has been reported in diverse species, across various sensory
modalities, and during different life-history stages. Due to this diversity, imprinting research uses
highly varied methodologies, with distinctive differences between the methods employed for
different types of imprinting. We systematically review relevant literature, identifying and
describing the range of methodologies used to study imprinting across taxa and modalities. After
compiling a representative dataset of 192 behavioral imprinting-focused experiments, we
categorize studies by imprinting modality, focal species, ontogenetic stage addressed, and
methods applied for both exposure and testing. The majority of studies in the sample focus on
filial imprinting in precocial birds but non-filial types, such as sexual or home range imprinting
in altricial and non-avian species are also present, albeit at far lower proportions. Filial
imprinting is studied across different sensory modalities, mostly through applying artificial
stimuli, but non-filial imprinting studies mainly use live animals as stimuli, without isolating the
relevant sensory modalities. Most studies of filial imprinting measure preference by spatial
proximity, following response, or the suppression of a fear response, whereas most studies of
sexual imprinting employ the attempt frequency of sexual behaviors. Finally, we analyze the
relative frequencies of methodological approaches in each imprinting category, to highlight
potential biases due to uneven research effort rather than intrinsic biology. The patterns and
biases in imprinting methodologies that we uncover hamper attempts to establish whether
different forms of imprinting share mechanistic foundations, including whether imprinting
constitutes a biologically meaningful learning category.
