In this interview, I talk with Lisa Leaver about her paper published in the Learning & Behavior Special Issue in Honor of Stephen Lea.

Transcription

Intro

Fazio: You’re listening to All Things Cognition, a Psychonomic Society podcast.

Now here’s your host, Laura Mickes.

Interview with co-Guest Editor Lisa Leaver

Mickes: I’m back with Lisa Leaver and I want to ask you, Lisa, about the paper that you wrote for the Special Issue of Learning & Behavior and the paper that you wrote, is called “Learning is Negatively Associated with Strength of Left/Right Paw Preferences in Wild Grey Squirrels.”

And they [the grey squirrels] came over, I had a little quick look at this, they came over in 1870, I think.

Leaver: Some of the dates differ depending on where you look, but it’s been about 150 years and there were multiple entry points in the UK.

Mickes: Why?

Leaver: There was a big trend for introducing species that people liked. You know you went on your travels, you found something cool, so you brought it back. Any of the birds mentioned in Shakespeare were brought to North America because, well, who knows why but that caused a lot of problems and squirrels have as well.

Mickes: But it’s a perfect opportunity for you to do your science.

Leaver: Yes.

Mickes: They’re a good participant for you.

Leaver: They are really good, yeah.

Mickes: Who’d have thought that when they’re bringing squirrels over on the ships [laughs] …

Leaver: [laughs]

Mickes: and 150 years, your grandchildren will be studied by Lisa.

Back to your paper. You were looking at the paw preference in squirrels.

Leaver: Yeah

Mickes: Will you give a little bit of background?

Leaver: So we were interested in what you might call laterality or handedness and it’s meant to be related to how highly lateralized your brain is. So if you’re really strongly left or right-handed, then your brain might be very strongly lateralized as well.

There are different theories about why we might be lateralized at all so that you might be improving efficiency by not processing things on two sides of your brain. You might specialize in things on one side and other things on the other side, which then allows you to be more efficient.

But there’s also some evidence that that can be quite costly from a fitness point of view. So there are costs in terms of some of the things that you can do as well. Really, not much work has been done. There’s been tons of work in humans,

Mickes: Yeah.

Leaver: but not much work in nonhuman animals. And most of that work has been in birds and fish.

We were interested in adding another mammal to that. So mostly, again, the work that has been done in mammals, I’ve mentioned humans, but primates and dogs. So we were interested in looking at what’s happening in mammals and whether there’s kind of a general rule about efficiency that crosses everything or whether there’s something special about mammals that differs from the fish and the birds adding another species to this comparative perspective, which again is really motivated by Steven’s [Lea] work and the sorts of things that he does.

Mickes: You used squirrels, obviously, as your participants and and so you tested whether they were right-pawed or left-pawed on some sort of the apparatus.

Leaver: Yes, we had a Perspex tube that was packed with peanuts, peanuts that didn’t have their shells on and they couldn’t stick their faces into the tube because the tube is too narrow and they’re really inclined to use their faces. So if you give a squirrel any kind of food, it will pick it up with its mouth and then put it into its paws and move it around. And then use its mouth to eat it. It holds food in its mouth when it digs a hole to cache it. Yeah, so they don’t want to use their paws much.

Leaver: So we had to kind of force that and we measured pawedness while we were measuring learning. So they had learning tasks combined with measuring left- or right-handedness at the same time. So they had to learn not to try to stick their faces into the tube and to use their paws to get the nuts out, which was the only way they could do that.

There were a couple that never learned.

Mickes: Oh,

Leaver: they tried and tried again and could not figure it out. Most of them learned, but they would persist – it was a really prepotent response to try to stick their faces in, and mostly they would do it every so often as a kind of test. Some of them would stick their tongues out really really far and chew around the edges and

Mickes: Oh, that’s so cute.

Leaver: Once they started using their paws, then we could measure how many attempts they were making with their left and their right paws and then we can create an index of how strongly left- or right-pawed they were.

Mickes: And then you looked at how long it took them to get to the solution.

Leaver: Yeah. You know, they varied in terms of how quickly they learned. Some of them learned really, really quickly and have really steep curves. Some of them learnt much more slowly and had really shallow curves. And so we had a kind of spectrum of how quickly they learned and we had a spectrum of how strongly left- or right-pawed they were. And we could look at the relationship between those two things.

So we found that the ones who were really strongly left- or right-pawed were the ones that had much more shallow learning curves. They weren’t learning as quickly as the ones who were a bit more what you might call ambidextrous.

Mickes: Oh, that’s really fascinating. Why do you suppose that is? If you’re really right-pawed or left-pawed that you don’t learn as fast? Is that the cost you’re talking about then?

Leaver: We don’t know why that is. My speculation is that it has something to do with flexibility. So the more flexible you are in your learning and behaviors, the better in certain situations. They’re again, an invasive species or a species that’s an omnivore and exploring various different food sources living in all sorts of different habitats needs to be able to learn quickly. So maybe that’s the cost of being strongly pawed.

Mickes: What struck me about your paper was that you had recruitment issues that only nine out of the 31 squirrels that you marked took parts you had 30% that took part. Do you think that the other 70% were just really lazy? Or smart? They’re like, look at that thing, I can’t get those nuts!

Leaver: We do have massive recruitment issues. I hope that they weren’t particularly strongly ambidextrous or handed. I’m, hopefully, they were a random sample of squirrels. But basically, because we set up this Bonanza food, whoever’s got their home range quite central to it, has an advantage. So you end up with these little despot squirrels who guard the apparatus and they’re the ones who use it on a regular basis.

So we would often have the dominant squirrel coming in first thing in the morning and using the device until it got bored of it. And then we can reload it and then we’d get a couple of other quite brave squirrels who would move in next.

Mickes: Oh.

Leaver: But the ones that were quite subordinate and far down on the dominance hierarchy just never came. So we had a few different locations to try to get different squirrels to come in. But you always end up with squirrels who are about, you know that they’re around but they’re not coming in.

There’s also some that we mark cause we, we track them and we mark them with hair dye so we know who’s who. But there’s some who are just moving through. So they were never going to come back. They just

Mickes: oh.

Leaver: we caught them and maybe they died or maybe they moved on.

Mickes: Okay, well that’s sad.

So then you mark more than you even expect to get.

Leaver: Yeah,

Mickes: that’s all fascinating.

Are you doing any follow-up studies?

Leaver: Not at the moment, no.

I am interested in all sorts of aspects of learning and foraging and assessment of risk in squirrels, so I’m kind of heading off in that direction at the moment.

I have a Ph.D. student, Mattie Yeo who’s interested in the handedness angle, so she is planning some studies for her Ph.D. to work on that.

Mickes: Oh, great. Okay, so I’ll stay tuned.

Thank you so much, Lisa. I really appreciate your time.

Leaver: You’re welcome. Nice to speak to you.

Concluding statement

Fazio: Thank you for listening to All Things Cognition, a Psychonomic Society podcast.

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Featured Psychonomic Society article:

Leaver, L. A., Ford, S., Miller, C. W., Yeo, M. K., & Fawcett, T. W. (2020). Learning is negatively associated with strength of left/right paw preference in wild grey squirrels (Sciurus carolinensis). Learning & Behavior. https://doi.org/10.3758/s13420-019-00408-2