The Nowicki Lab at Duke University



Signal Perception & Function

The world of sensory information is complicated and messy. Animals are confronted with an overwhelming barrage of physical stimuli that they must sort through to make use of the important stuff, especially in the context of communication. One focus of our work is on categorical perception, a process by which continuous variation in a physical stimulus is parsed into discrete perceptual categories. For example, using swamp sparrows as a model system, and in collaboration with Rich Mooney's lab at Duke, we've shown that neurons in area HVC of the songbird brain show the same categorical discrimination of song note types the birds themselves exhibit in behavioral tests. We've also shown that perceptual category boundaries vary geographically and—even cooler—we've shown that how a bird categorizes a note type depends on where in the song that note occurs. Both properties had previously been thought to be unique to the perception of human speech phonemes.

We've extended our work on categorical perception to visual signals, asking whether female zebra finches discriminate colors from orange to red in a continuous or a categorical fashion. This color palette is significant because zebra finch beaks vary from orange to dark red depending on their carotenoid content, and females pay attention to male beak color as part of their assessment of a male's quality as a potential mate. Models of assessment signaling often assume that signal receivers respond to continuous variation signals in an equally continuous fashion. Our work, done in collaboration with Sönke Johnsen's lab at Duke, shows that this is not necessarily the case.

Here are some of our papers on mechanisms of signal perception and production:

Zipple MN, Caves EM, Green PA, Peters S, Johnsen S & Nowicki S. 2019. Categorical perception across non-signaling versus signaling color ranges in a songbird. Proceedings of the Royal Society London B 286: 20190524 doi:10.1098/rspb.2019.0524

Caves EM, Green PA, Zipple MN, Peters S, Johnsen S & Nowicki S. 2018. Categorical perception of carotenoid-based coloration in an assessment signal. Nature 560: 365-367 doi:10.1038/s41586-018-0377-7

Lachlan RF & Nowicki S. 2015. Context-dependent categorical perception in a songbird. Proceedings of the National Academy of Sciences, USA 112: 1892-1897.

Prather JF, Peters S, Mooney R & Nowicki S. 2012. Sensory constraints on birdsong syntax: neural responses to swamp sparrow songs with accelerated trill rates. Animal Behaviour 83: 1411-1420.

Prather JF, Nowicki S, Anderson RC, Peters S & Mooney R. 2009. Neural correlates of categorical perception in learned vocal communication. Nature Neuroscience 12: 121-128.

Prather JF, Peters S, Nowicki S & Mooney R. 2008. Precise auditory-motor mirroring in neurons for learned vocal communication. Nature 451: 305-310.

And here's a useful commentary on our recent work on categorical perception of color in birds:

Kelber A. 2018. Birds perceive colours in categories. Nature 560: 311-312 doi:10.1038/d41586-018-05811-9


Nowicki Lab
Department of Biology
Box 90338, Duke University
Durham, NC  27708-0338  USA
Lab phone: 919-684-6950