Cologne as a pungency control in tests of chemical discrimination: effects of concentration, brand, and simultaneous and sequential presentation

Abstract

Cologne has been used extensively as a pungency control in experiments on chemosensory behavior to assess responses to an odorous, readily detectable stimulus that is irrelevant to the adaptive response being studied. However, undiluted cologne may be aversive, its effects might differ among brands, it might suppress responses to simultaneously presented chemical stimuli, and might affect subsequent responsiveness to other stimuli. We present experimental data showing that undiluted cologne can be aversive, but that aversion can be eliminated by dilution. We also show that the utility of cologne as a pungency control varies among brands, that cologne does not suppress responses to food chemicals in some species, but does in others, and that prior exposure to cologne does not affect later response to food chemicals. In 60 s swab trials with the Balearic lizard (Podarcis lilfordi), the main chemosensory responses were unaffected by cologne concentration. However, one-fourth of lizards exhibited slight to moderate aversion to undiluted cologne and 3:1 water:cologne, but not to a readily detected lower concentration (9:1). Two cologne brands did not affect responses, but a third brand induced increased tongue-flick rates. Colognes that stimulate increased tongue-flicking might mask real experimental effects. Cologne presented simultaneously with cricket chemicals did not affect tongue-flicking and biting responses in two species, but caused increased tongue-flicking in a third species and weaker response to cricket chemicals in a fourth. Prior testing with cologne did not affect responsiveness to cricket chemicals in a subsequent trial. Although cologne is a useful pungency control, pilot tests are needed to verify its utility for unstudied cologne types and animal species.