Some rats are ticklish than others – and you can tell by this how much they squeal with laughter.
- Rat call patterns could be used to measure their emotional response to actions
- They make a series of high frequency sounds in response to tickling
- This is similar to human laughter, but it was impossible to tell if the rat likes it
- Researchers have now linked the number of squeaking noises to emotional reactions
According to a new study, you can tell if a rat likes to be tickled and how emotionally it will respond to the situation by listening to its squeaking noises.
Bristol University researchers used a behavioral test on laboratory rats that measures their emotional experience as they tickle them and watch for squeaks.
Rats emit high frequency vocalizations that, when generated during a human simulated game or "tickle", resemble human laughter.
Until now, without a time-consuming and lengthy behavioral study, it has been impossible to know how much an individual rat likes to be tickled.
The Bristol team says their new technique could allow scientists to determine a rat mood by simply tickling them and listening to their squeak frequency.
Bristol University researchers tickled behavior-assessed rats and later stopped their squeaking to find a link between tickling and vocalizations
According to a new study, you can tell if a rat likes to be tickled and how it will respond to the action by listening to its squeaking noises. Image from a picture agency
Not all rats like to be tickled, and some make high numbers of calls while others didn't, and the calls are directly related to their emotional experience, the team found.
As part of their study, the Bristol team answered the question “Do rats like to be tickled” and compared it to human laughter when tickled.
Human laughter is complex, and when a person is tickled, they can laugh even if they don't find the experience pleasant. .
Rats that made the most calls showed the highest positive emotional response to tickling, but those that made no or few calls showed no positive response.
Emma Robinson, who led the research, said the ability to measure a positive emotional response in animals is an important way to improve their well-being.
“Rats uttered voices in response to tickling accurately reflect their emotional experience and are easy to measure.
"Should this be the case in other situations, measuring vocalizations could provide the simple, graduated measure of emotional experience needed to better understand and improve rat well-being in a laboratory."
In the context of tickle-induced laughter in rats, the team's findings support previous work showing that these vocalizations indicate a positive experience.
However, rats seem to be more "honest" than humans with their response to tickling, and the amount of laughing at them depends directly on how positive they find the experience.
Being able to accurately and objectively assess animal welfare is important, but difficult to achieve, according to the team.
The Bristol team used a behavioral test that measures an animal's emotional experience and compared the results to rat squeals that are triggered during the tickling. Image from a picture agency
Without being able to ask an animal how it feels, researchers have to rely on other methods that have their limitations.
Researchers in Bristol have previously shown that the affective bias test used in this study can provide this type of objective measurement, but it is highly specialized and time consuming to perform so it cannot be readily applied in the broader laboratory animal setting.
This research found that human simulated play or "tickling" of rats can cause a positive emotional state, but not all rats.
By recording vocalizations, it is possible to quickly identify which animals benefit from this type of enrichment in a laboratory setting.
In the future, the research team would like to investigate whether there are similar associations between vocalizations and positive and negative emotional experiences.
The results were published in the journal Current Biology.