There's more to a pig's oink than meets the ear, with happier porkers making more noise than grumpy ones, scientists have found.
It also emerged that pigs with curious temperaments were more likely to grunt and squeal than their less inquisitive pals, the Daily Mail reported.
The research is hoped to help assess how happy pigs are in their living quarters.
To test their theory, scientists from the universities of Lincoln and Belfast studied 72 male and female juvenile pigs.
Half of the pigs were placed in spacious, "enriched" pens with straw bedding.
The other half were put in more compact 'barren' pens, with partially slatted concrete floors which were in accordance with UK welfare standards.
To test the pig's personalities, the researchers carried out two tests.
One involved placing a pigs in a pen for five minutes with objects they had not encountered before - these were a large white bucket or an orange traffic cone.
Their behaviour - including their grunts - were then measured.
The tests were repeated a fortnight later to see if the pigs' behaviour was consistent.
The study found pigs with more 'proactive' personality types - who were keener to explore their environment - produced more grunts than the 'reactive' animals.
It also found male pigs kept in the lower-quality conditions made fewer grunts than those in the enriched pens.
Dr Lisa Collins, a specialist in animal health, behaviour and welfare epidemiology in the School of Life Sciences at the University of Lincoln, said: "The domestic pig is a highly social and vocal species which uses acoustic signals in a variety of ways; maintaining contact with other group members while foraging, parent-offspring communication, or to signal if they are distressed.
"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.
"Grunts occur in all contexts, but are typical of foraging to let other members of the group know where they are."
Mary Friel, lead author of the study added: "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."
The research was published in the Royal Society journal Open Science today.