Pigs are extremely interesting animals. They're able to solve challenging problems, they love to play, they display a wide range of emotions, and they have unique individual personalities.

Until now, many of the data stemming from detailed behavioral studies of pigs have been scattered about in scholarly literature, in popular essays and summaries, or summarized in books including Sy Montgomery's The Good Good Pig: The Extraordinary Life of Christopher Hogwood and Barry Estabrook's Pig Tales: An Omnivore's Quest for Sustainable Meat, a book I recently reviewed.

I also considered some aspects of pig "smarts" and emotions and what we can make of comparisons among different species in an essay called "Are Pigs as Smart as Dogs and Does It Really Matter?" A good deal of research on pigs centers on their welfare, because pigs are used globally for food and are treated none too kindly.

I love pigs and try to keep current on research on these fascinating animals. Thus, I was thrilled to learn of a review essay published just this week by researchers Lori Marino and Christina M. Colvin called "Thinking Pigs: A Comparative Review of Cognition, Emotion, and Personality in Sus domesticus." Because this paper is available online, my main purpose is to call to this most valuable review article and to highlight some of its very interesting and fascinating findings.

The summary of the above essay reads:

"While relatively little is known about the psychology of domestic pigs, what is known suggests that pigs are cognitively complex and share many traits with animals whom we consider intelligent. This paper reviews the scientific evidence for cognitive complexity in domestic pigs and, when appropriate, compares this literature with similar findings in other animals, focusing on some of the more compelling and -edge research results.

"The of this paper are to: 1) frame pig and psychology in a basic comparative context independent of the livestock production and setting; and 2) identify areas of research with pigs that are particularly compelling and in need of further investigation. ... We conclude that there are several areas of research in which the findings are suggestive of complex psychology in pigs. We conclude by calling for more noninvasive cognitive and behavioral research with domestic pigs in non-laboratory settings that allow them to express their natural abilities."

To accomplish its goals, "Thinking Pigs" considers a wide variety of topics including the domestication of pigs, their sensory abilities, learning skills, time perception, spatial learning and , novelty seeking, inquisitiveness and play, social cognition and complexity, self-awareness, and .

The authors conclude, "Pigs display consistent behavioral and emotional characteristics that have been described variously as personality. e. ., coping styles, response types, temperament, and behavioral tendencies."

Concerning the emotional lives of pigs, they note, "Some of the more interesting studies demonstrating emotional contagion in pigs involve responses to other pigs’ anticipation of positive or negative events, revealing the importance of social factors in emotion. In one study, naïve test pigs were exposed to pen mates who had been trained to anticipate upcoming rewarding events (receiving straw and chocolate raisins) or aversive events ( ). When the naïve pigs were placed in the company of the trained pigs they adopted the same emotional anticipatory behaviors (e.g., ear and tail postures, increased cortisol release) as the trained pigs with the direct experience. These findings show that not only can pigs connect with the emotions of other pigs, but they can also do so with pigs who are responding emotionally in anticipation of future events (Reimert, Bolhuis, Kemp, & Rodenburg, 2013)."

"Thinking Pigs" not only summarizes much of what is known about pig cognition and emotions, but it also suggests areas in which future research is needed so that we can learn more about pigs and see how they compare to other animals. These areas include:

and comprehension of symbolism and the meaning of various combinations and sequences of symbolic cues

The ability to not only anticipate an event but to prepare or plan for an event behaviorally

The capacity for numerical understanding, particular in a foraging situation

Play and exploration and how different forms are combined and are related to social relationships

Taking the perspective of a conspecific or human, including understanding eye and head orientation as it relates to attention

Understanding and using pointing and other indicating actions by humans

Parameters of emotional contagion and the presence of cognitive

Personality structure as it compares with other species, including humans

All in all, "Thinking Pigs" is a most welcomed addition to the research literature and I hope it enjoys a wide readership.

The teaser image is of the author and his friend, Geraldine, a rescued pig he met at Kindness Ranch, a sanctuary for former research animals.