Communication among animals (aka, I wasn’t droppin’ no eaves sir, honest.)

cocktail party

I have terrible hearing. I’m not hearing-impaired in any actual way, but whenever there is a lot of background noise – terrible music at a bar, the burbling of friends at a big party – I just cannot understand what people are saying even when they’re right nearby. I honestly spend most of time responding to what I guess they’re talking about. But this ability to separate what a friend is signaling from the background noise is not just a problem most of us are able to solve at “cocktail parties” but is also something that ubiquitous technology like cell phones have been developed to cope with.

A less understood problem is not how to detect and understand these signals, but how to convey them. Should you speak really loudly? Have a particularly distinctive voice? This is something that animals in the wild have to deal with all the time. Among the cacophony that is multiple species trying to chatter at each other, they have to decide how to send messages to each other that are both detectable and understandable from the background noise.

The traditional view has been that animals will act like to channels: partition the space so that they don’t interfere with each other too much. This bird over here will squawk loudly, this dove will coo softly, and so on. That would be the most informative way if each species were acting on their own. But of course there are other things to consider. Two birds may occupy the same ecological niche, worried about the same predators and needing to warn off other animals that are battling for the same food. If that was the driving evolutionary pressure, signals might end up more clustered than you’d otherwise expect.

In fact, the latter possibility is exactly what happens. Tobias et al. visited the Amazon and recorded the dense vocalizations of more than 300 animals throughout the day. Taking the principal components, they found that the three most relevant ways to describe the data are in pitch, duration, and pace of the signal. In fact, there is much more clustering than you’d expect from animals partitioning their signal. Although they are not able to test it directly, this suggests that there could be a lot of communication between different species. This interspecies communication shouldn’t be too shocking: we all understand a growl when we hear it, right?

Informationally-optimal filters for natural sounds (left) and experimentally measured cochlear filters (right)

Informationally-optimal filters for natural sounds (left) and experimentally measured cochlear filters (right)

One of the fundamental questions in neuroscience is how our sensory neurons are able to represent the world. An extremely fruitful line of research has been to study how neurons respond to natural stimuli. It makes sense, then, that sensory neurons have evolved to represent as much information as possible about the natural world – after all, why would you throw away information right away? An influential paper by Michael Lewicki proposed an answer for audition by finding the independent components of natural sounds. But no one has thought about this in an ecological context! Natural sounds have to compete – or cooperate – with vocalizations from other animals. Hopefully we will see evidence of that in the future.


Tobias JA, Planqué R, Cram DL, & Seddon N (2014). Species interactions and the structure of complex communication networks. Proceedings of the National Academy of Sciences of the United States of America, 111 (3), 1020-5 PMID: 24395769

M Lewicki (2002). Efficient coding of natural sounds Nature Neuroscience DOI: 10.1038/nn831

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Learning neuroscience without being talked down to

Whenever a nonscientist friend sends me something to read about neuroscience, I usually smile weakly and pretend to read it. Sure, these articles are interesting but they are often imprecise and not as packed with information as I would like. Neuroscience is a large and deep field, and while I know some fraction of it quite well, there is much more that I do not – and the best way to learn about it is to hear from the experts who are not trying to talk down to you.

I guess the field is maturing enough that we are now starting to have access to regularly updated shows in this format. One, in video format, is with the most recent video posted above. It looks pretty great so far and has a kickstarter for funding to create more episodes. Seriously, go donate.

The other is an interview podcast series by the students at Stanford Neuroscience called NeuroTalk. Every week or so, a neuroscience seminar speaker visits Stanford to give a talk on their work; the students have decided to interview the speakers, have them give a concise description of what they do, and get them to chat for a bit. It’s a fantastic idea and something I wish my current university did…  Here is someone who does decision-making, for example.

Beyond this, you can often see recorded lectures just by going to youtube and typing in a scientist’s name… it is often worth it.

Plants are people too

Ever since I started studying neuroscience, plants have always fascinated me.  These guys don’t have a nervous system, really, but they are able to do a lot of things we would normally expect to require a nervous system.  A recent book – which I hope to read soon, by god I put it near the head of my 300+ goodreads “to read” list – has a lot to say on how plants experience the world:

When Chamovitz introduces the baffling way that irises appear to “remember” what color of light they last saw or how the parasitic plant dodder (Cuscuta pentagona) can “smell” whether it’s next to a tomato (one of its preferred hosts) or a stalk of wheat, it’s hard not to share his enthusiasm for unraveling these mysteries. He elaborates on elegant early experiments in plant biology as well as modern-day discoveries, providing a window on the work of the many scientists who clarified the mechanisms driving these perplexing phenomena. The latter include the use of genetic mutants of the botanical workhorse Arabidopsis to unveil 11 different photoreceptors that allow the plant to discern, among other things, whether it was last exposed to the red light present in the morning or the far-red light present in the evening. Finely tuned gas chromatography has revealed how dodder differentiates between the attractive chemicals in eau de tomato and the repulsive ones ineau de wheat.

…Consider proprioception, the sense of the relative position of our body parts in space that allows us to complete coordinated movements without tripping over our own feet. Do plants have something like proprioception? Certainly, says Chamovitz, but for plants, it’s about the position of their parts relative to gravity.

Photoreceptors?  Odor receptors?  Proprioception?  These all seem like fundamental attributes of our sensory nervous system.  And yet what use does a plant have for a nervous system?  It moves too slowly to really need one, I imagine.  They can also sense and communicate with each other in a way that seems similar to how bacteria sense and communicate with each other.  I imagine we have  a lot to learn from plants about basic principles for nervous system integration of social and sensory inputs.

PS. There’s more here!