Many studies have shown that behaving badly (e.g. shouting, hitting, pushing…) with an animal increases the fear that this animal has for humans. On the contrary, being soft with animals increases their willingness to interact with us.
But how do animals perceive those gentle interactions?
Answering this question was the aim of one of my research projects.
To complete my mission, I cuddled a group of pigs three times a week over 9 weeks, to habituate them to positive human contacts (strokes and scratches). I wanted to compare the habituated pigs to a group of naïve pigs, which lived in the same room but did not get positive contacts.
After the 9 weeks, all the pigs underwent anesthesia so that their brain could be scanned in an MRI*. During the scans, I stroked the back of all the pigs. We used the images produced to look at the brain areas that are active during the stroking, and compare the level of activity between the groups.
We found out that brain areas associated with the processing of pleasant events were activated during the stroking of all pigs, and that this activation was even greater in the habituated pigs.
Even cooler: The pigs which did not experience stroking before (“the control group”) were also surprised by being stroked on the back, as their amygdala was more activated than habituated pigs. This further supports that the greater pleasant response of habituated pigs is due to their experience with human contacts.
Altogether, we showed that the brain of sleeping pigs consider the stroking on the back as a pleasant event, and even more when it has been experienced before.
In a nutshell: stroking on the back is nice for pigs !
* Magnetic Resonnance Imaging: this machine is basically a giant magnet which sends radio waves into the scanned subject’s body. Those waves displace the hydrogen protons in the subject’s body, which produce electromagnetic signals. Those signals are different according on the type of tissue (water, muscle…), which is translated by the machine into an image of the inside of the body – in our case, the brain of the scanned pigs !