Ever wonder why some pigs grunt more than the other pigs? And has it ever occurred to you that "oink" might actually mean something?

Researchers from the University of Lincoln and Belfast analyzed 72 juvenile pigs to shed light on this matter.

Apparently, the grunts have something to do with each pig's personality. The more the pigs oink, the happier they are, which means when they oink they are sort of saying "Thank you for feeding me and I am very happy with my house now."

The study also revealed that those who make less noise are the grumpy ones.

The Daily Mail notes that the researchers were able to come up with this conclusion by conducting two separate experiments. They placed half of the pigs in "enriched" pens, while the other half in compact" pens.

The first experiment revealed that the frequency of their grunts depend on the quality of the environment they are in. Meaning those in the "enhanced" environments produced more grunts that those in poorly set pens.

The next experiment involved placing the pigs in a pen for five minutes with objects they had not encountered before. The study found the more proactive pigs, or those who are eager to explore their environment, produced more grunts than their "reactive" counterparts.

"The sounds they make convey a wide range of information such as the emotional, motivational and physiological state of the animal. For example, squeals are produced when pigs feel fear, and may be either alerting others to their situation or offering assurance," said principal investigator Lisa Collins, a specialist in animal health, behaviour and welfare epidemiology in the university's School of Life Sciences, as per Science Daily.

She added that grunts can happen in different contexts, but are usually done during foraging to let other members of the group know their location. 

The study implies that when studying animal behavior, their vocalization is important and must be considered at all times to understand them more.

Mary Friel, also one of the authors, added: "The aim of this research was to investigate what factors affect vocalizations in pigs, so that we can better understand what information they convey. Understanding how the vocalisations of pigs' relate to their personality will also help animal behaviourists and welfare experts have a clearer picture of the impact those personalities have on communication, and thus its role in the evolution of social behaviour and group dynamics in social species."

Pig cognition has been studied over time. Previous researchers revealed that they are actually smart, like dogs and chimpanzees.

For instance, they have a good memory so they are able to remember where food is located whenever foraging.

The New York Times also noted that pigs can quickly learn how to use mirrors and will use it to reflect their surroundings and look for food.