People have wonderful fingertips. They’re delicate and will be moved over objects to really feel its softness, texture, dimension and form. These actions are each advanced, and “task-specific”. Because of this you undertake totally different actions relying on what you need to really feel about an object. We squeeze or push objects to guage softness, and really feel across the edges of objects to guage dimension and form. And for those who wished to really feel the feel of an object, you’d sweep your fingertips over the floor.
Having the ability to undertake totally different motion methods reveals that we are able to exactly management our fingertip actions and draw on our previous experiences in an effort to take note of essential points of an object – the sides of shapes and the surfaces of textures, for instance. Because of this we’ve got a excessive degree of management over our sensory notion, and we name this lively contact sensing.
Contact sensing in mammals
Most mammals don’t have as moveable or delicate fingertips as people. As a substitute they’ve whiskers, that are contact delicate hairs on their faces, and used to information locomotion, foraging for meals and to discover objects.
Neuroscientists have been finding out whiskers for many years, particularly in laboratory rats and mice, making an attempt to grasp how alerts from the whiskers are processed within the mind. However solely now are we realising that whiskers are additionally moved with wonderful methods, identical to our fingers.
Rats, mice, and another mammals, can transfer their whiskers in a to-and-fro scanning movement known as “whisking”. Whisking is likely one of the quickest actions that mammals could make, occurring as much as 25 occasions per second in mice.
When rats and mice contact objects in addition they undertake different whisker actions. These embody bunching up their whiskers to make extra of them contact a floor, making mild touches to allow clearer alerts towards a floor, and slowing down whisker actions so that they contact the floor for longer.
However nobody knew whether or not animals might adapt their whisker actions particularly for various duties.
Such “task-specific” actions could be an thrilling discovery as it might point out a exact degree of management over their sensors and notion.
Selecting a candidate species
Step one in answering this essential query was to decide on a possible candidate species for our investigation.
Pinnipeds, together with seals, sea lions and walruses, have whiskers which might be notably thick and lengthy, making them simpler to measure than these of smaller mammals reminiscent of mice.
Additionally they have among the most delicate whiskers of any mammal – they will detect textures and shapes to the identical sensitivity as human fingertips, even in chilly water when our fingers would go numb.
They’re additionally moveable. We’ve beforehand discovered that California sea lions make the largest and most managed actions with their whiskers, when in comparison with harbour seals and Pacific walruses.
These elements, plus their means to carry out object-discrimination duties – the place they may distinguish between objects primarily based on dimension and form – made California sea lions the perfect topic for our investigation on task-specific whisker actions.
Our work with Lo
For our research
we used a sea lion, Lo, for the total complement of experiments. Having just one particular person is frequent in marine mammal research, however it does put stress on the investigators to gather good high quality and extremely quantitative knowledge from that one particular person.
Lo was skilled to finish a texture-discrimination activity utilizing solely her whiskers.
She needed to discover a medium-textured, fish-shaped object amongst different distractor fish. She additionally accomplished a size-discrimination activity of discovering a medium-sized fish amongst different distractors, and a visible activity of discovering a gray fish amongst different colored distractors (sea lions use very small whisker actions in visible duties).
Lo was filmed doing the duties hundreds of occasions, and her whisker and head positions had been tracked within the video footage.
Wanting on the knowledge and the video footage it was clear that Lo made task-specific actions together with her whiskers. She made sweeping actions over textured surfaces, and felt across the edges of the totally different sized shapes. These particular motion methods are additionally utilized by people with our fingertips.
The power to change whisker exploration methods between tactile duties enabled Lo to finish the duties effectively. Lo discovered the right fish in nearly all trials and made choices shortly, in below half a second. Video footage of the opposite sea lions additionally confirmed them using the identical methods, so we expect that this could be frequent amongst California sea lions on the whole.
And now different animals
Seeing the identical motion methods conserved from sea lion whisker actions to human fingertip actions showcases how essential these methods are for enhancing contact alerts throughout totally different duties.
It’s probably that different species of Pinniped will be capable of make task-specific whisker actions, since in addition they have delicate, moveable whiskers. We’re investigating this now, together with different species of carnivores, reminiscent of otters.
That is the primary time that task-specific whisker contact sensing has been documented. It demonstrates that finding out whiskers can provide us essential insights into animal motion management, in addition to their notion and cognition.