Hi Simona,

When you start thinking about invertebrate behavior, it is typically best to revert to true stimulus-response arcs through highly modular brains built upon tightly clustered ganglion. Even with regards to truly large macro-invertebrates, such as cephalopods like the giant squid, the brains demonstrate great functional compartmentalization and so interpreting their suite of behaviors as including "sociability" is risky. While one could state a giant squid demonstrates complex behaviors, those behaviors have been exquisitely refined by selective forces for longer than mammals have existed.

When we turn our eyes to vertebrates, something interesting happens; with expanding size and increasing plasticity, the lines defining different components/compartments within the brain necessarily blur and we detect emergent properties that by themselves may alter connectivity through ontogeny. It is when some of those emergent properties assert themselves, primarily through intense inter-connectivity throughout multiple regions acting in concert that we detect behaviors that move from the extremes of behaviorism and into the realm of cognition. This may seem, at first contrary to common knowledge; it is widely known that cephalopods are excellent problem solvers (opening jars, box tops, and navigating mazes to obtain food). However, the actions they employ are already a part of their genetically endowed complement of behaviors needed for survival in "the real world" as opposed to the laboratory (or experimental circumstances set up by researchers in the open waters). Thus, "problem-solving" does not necessarily equate to cognition, nor does it imply the potential for truly social behaviors.

In the vertebrates, especially in the mammals, we see something new - something interesting. The emergent properties of intense inter-connectivity through myriad specialized neurons capable of processing information in numerous ways has granted an interesting network known as the "mirror neuron system" that, when operating in conjunction with Von Economo neurons, permit the rise of what you would more normally call "sociability" (i.e. behaviors of *conscious* social importance).

Let me give you a little something from a project I am currently writing...

The mirror neuron system (MNS) permeates the cerebral cortex of human and nonhuman primates and deeply connects the ventral premotor cortex, primary somatosensory cortex, and the anterior, inferior, fronto-, and temperoparietal regions, (Mukamel et al., 2010; Turner, 2013). The orbital frontal lobes, limbic system, and insula are interconnected through the MNS (Chong, Cunnington, Williams, Kanwisher, & Mattingley, 2008), and this system activates while witnessing another’s behaviors, resulting in ‘mirrored’ somatosensory and proprioceptive feedback mapped onto the ‘self’ (Fogassi & Ferrari, 2007; Rizzolatti & Destro, 2007). This cortically pervasive system enables the empathic experience of another, provides the means by which to interpret communicative facial and body gestures, and is modulated by motivation and emotion (Decety, Norman, Berntson, & Cacciopo, 2012; Decety & Meltzoff, 2012).

An important set of related neurons, theVon Economo neurons (VEN), which may exceed 1x10-3 meters (1mm) in length (Watson, Jones, & Allman, 2006) and are found in all primates, ceteceans, elephants, and other mammals with complex social dynamics (Santillo, Nilsson, & Englund, 2013). VENs are bipolar neurons found principally in layer V that reciprocally connect the anterior and midcingulate gyri (ACG and MCG), anterior insula and frontal insula (AI and FI) (Bernhardt & Singer, 2012; Nimchinsky et al., 1995, 1999) dorsolateral prefrontal cortex (dl-PFC) (Fajardo et al., 2008).

Anterior insula and anterior cingulate are activated by situations that involve social error, a deficit in the social network in which the individual is participating, or a change in the state of another participant. For example, these structures are activated by resentment (Sanfey et al., 2003), deception (Spence et al., 2001), embarrassment (Berthoz, Armony, Blair, & Dolan, 2002), guilt (Shin et al., 2000), and observing another’s suffering (Singer, Seymour, O’Doherty, Kaube, Dolan, & Frith, 2004). The AI activates when a mate or close companion fails to reciprocate co-operative behavior (Rilling et al., 2007), but also when that close associate employs pro-social signals associated with mating, warm physical contact, and reliance (Bartels & Zeki, 2004; Singer et al., 2004).

The AI is also linked to the mirrored perception of pain (Gu et al., 2012). In another aspect of the VEN network, the FI is strongly activated by negative feedback in the form of frowning faces (Fiehler,Ullsperger, & Von Cramon, 2004), faces demonstrating disgust (Jabbi, Bastiaansen, Keysers, 2008), and when attempting to discern intention by facial expression (Baron-Cohen, O'Riordan, Stone, Jones, & Plaisted, 1999). Changes in affect are detected on an individual’s facial or body orientation and many emotional states may be detected through visual observation with high degree of accuracy in humans and chimpanzees, though this ability is often inhibited in those with developmental disorder (Bölte et al., 2006; Ekman & Friesen, 1978; Parr, Waller, Vick, & Bard, 2007; Vick, Walker, Parr, Pasqualini, & Bard, 2007; Reed, Sayette, & Cohn, 2007). Previous fMRI and PET brain-mapping of human emotional states reveal matching regional patterns on nonhuman great ape brain maps for happiness, fear, anger, sadness, care, and play (Damasio, Tranel, Grabowski, Adolphs, & Damasio, 2004; Murphy, Nimmo-Smith, & Lawrence, 2003; Panksepp, 2003; Phan, Wager, Taylor, & Liberzon, 2002). Because VENS are a functional component to an individual’s ability to read emotions on another’s face, witness and mirror the response to pain, and assess reciprocal material and social exchange, it seems that VENS may play a role in how the broader MNS derives understanding of socioemotional potential.

As you were asking about "personality", an article just published that explores personality from an evolutionary perspective (comparison across multiple primate models) that I thought you might enjoy:

http://psycnet.apa.org/psycinfo/2013-16347-001/

I generally agree with Jeffery's response, but I'll add a different perspective using a much more flexible definition of "sociability". Certainly invertebrates don't show the same kinds of complex social behaviors as those facilitated by the mirror neuron system in primates. However, on a basic level, many invertebrate species do show consistent differences in social behavioral patterns among individuals. Interpreting these behavioral differences as "sociability" is problematic, but they certainly involve social behavior. And these inter-individual differences have well-documented ties to brain region structure.

In eusocial hymenoptera, for example, social aggression is correlated with mushroom body volume (Molina & O'Donnell, 2007, 2008). One could not classify this as a difference in "sociability as a personality trait", but it still seems relevant to your question. Social aggression in hymenoptera might be interpreted as a measure of "social engagement", and differences in mushroom body (MB) volume seem to explain most of the inter-individual differences in this behavior. Moreover, the MB volume (and the level of social aggression) are plastic within an individual over its lifetime, suggesting the concepts of "personality" or "behavioral syndromes" might be quite different in some kinds of invertebrates than in vertebrates.

That's a great response, Adrienne. As I look back over my original response, in truth I focused too much on the concept of "personality" at the expense of the *social* side of "sociability". The problem with using the term "personality" is that there is the implication that organism can be thought of as a "person", thus demonstrating some level of intentionality, including the ability to direct the 'self' in behaviors that may exist in discord with selective fitness (a dolphin expending needed calories in the act of ferrying a human to a beach, taking the risk that the human will not behave as a predator during the situation, while limiting mating opportunity and foregoing fish acquisition). In the case of hymenoptera, it is unlikely that we will ever note a small collection of workers that rise up in solidarity against their queen and fight their way to freedom and establish a pack system as opposed to the hive - that is to say, I do not suspect bee intentionality will ever be.

Thank you for your answers. However, I am still lost...when trying to put the evidences from literature to a sensible entity :-(

I love the fact that social insects like some wasps have face recognition. Face patterns are I think in at least one paper I read the abstract of, hive specific and the pattern is used to discern hive vs nonhive members for the purpose of eliciting aggressive defenses. Their aggression is modulated, not robatically on or off in response to one stimulus. The face seems to be an important focus for many social animal, not just humans. I think we still are more biased towards thinking that terms like "personality" and "social" some how have to be like in humans to be "good" terms. Humans are just one species outcome of natural selection shaping a social species. OUR TRAITS came from precursor traits in other animals. We are not above nature genotypicaly. It would be more useful to think about our place on a continuum of personality and sociality or perhaps some part of a mosaic of traits, albeit with not surprisingly some innovative features that are certainly interesting, rather than describing humans as having some uniquely superior state of being.