A working definition of BLENDING in dissociative identity disorder would be a state where two alters are in control of the body at the same time and there is some mixture between them. CO-PRESENCE would describe when two alters are simply present. The experience of blending seems to vary among people with DID but the effect is usually some combination of the characteristics of both alters. I'll describe my system's experience with blending below but first, here's a thread of this phenomenon: http://www.psychforums.com/dissociative-identity/topic69907-10.html
In my system, blending has happened accidentally. Only once did I deliberately try to blend before I even knew what it was. Jack was in executive control and I tried to step forward with him. Both of us immediately felt this was very creepy and less than a minute later, I stepped back. It felt like we were pressed up against each other, or I was hanging around his neck or something. Not pleasant.
Other than the time just mentioned, when blending happens, whoever blends also gets stuck together. Trying to unstick usually results in a DID headache but in any case, separation isn't successful and it has to just kind of dissolve. If the blend doesn't involve me, the host John, I get pushed back further than when just one alter is in executive control. Sort of like the consciousness has only so much space. Five or six alters out at the same time, or even all paying attention at once, feels like an impossibility in my system, at least for now.
When two non-littles are in the body at the same time, there's a recognition of a need to cooperate. But the littles don't quite get that so blends with them can be kind of "messy" and feel random. The body control is not very good when we blend with a little.
John and Jack. Because Jack has a strong accent, the first accidental blend of both of us was very disconcerting. We often speak aloud to communicate to one other and we did that night. The accent was literally halfway between the two. The grammar, however, was mostly one or the other and usually matched with whoever's thought was being voiced. We were afraid we might stay blended. We were both concerned the weird accent could stick and how could I possibly explain that where I work. We were both there as separate individuals but it was hard to determine whether some sentences were said by one or the other. We could also pretty much talk back and forth in real time. Him commenting how weird it was, me wondering aloud what we were going to do. Thankfully, it only lasted a few hours.
John and Jonathan. Strange blend but we're not radically different people. Due to his past behavior of influencing me, it wasn't so terribly disconcerting to have him so near me, squished next to me. Considering I am gay and he is straight, however, we found that while we were blended we really didn't have much sexual response at all, as I recall. It was as if our opposite sexualities cancelled each other out for the time being. It was probably best that happened because Jonathan is normally very upset by my random background gay-oriented thoughts when he's out. We got stuck together for many hours and eventually went to sleep blended. In the morning only one of us was in the body by himself, so that was a relief.
Jack and Little John. What a giggle-fest that was. Jack described it as a funny little kid crawling all over him. He laughed and laughed, and Little John was overjoyed to be so close to someone who is protective of small children and has proactively stepped in when a little gets upset. Also, Jack is about the age that an older cousin was when Little John was host so he seems to have trusted him from the start.
Jack and Adam. Due to something I had been reading, Adam slipped alongside Jack when he was getting coffee for me one morning on campus. He still doesn't like to drink it but knew I did. Jack said he felt like a drunken sailor because Adam couldn't really walk at that point and it was very difficult for Jack to control the body. He did well just to get away from the counter without drawing massive attention to us.
Dan and Little John. Little John stepped in while Dan was walking and Dan, who was usually quite angry, could not help but feel very, very softened by the sweet little kid's presence. Like Jack, he laughed and laughed at the experience, but was less comfortable than Jack with the whole thing.
Dan and Adam. Immediately after Little John was blended, Adam somehow pushed forward and took his place blended with Dan. It had already become apparent to everyone in the system that although Dan was a pretty angry alter, often gritting his teeth and wanting to punch male adults as they passed him (though he has never actually done that), when a small child or a woman would pass by, he would go all soft, making sure his face was welcoming and friendly, not angry and scary. I can only guess that Adam was aware of Dan liking little small children, feeling protective of them, and wanted to get close to him. Adam is a sweet, innocent baby and for Dan it felt something like hugging a baby very close to your face and inhaling his sweet smell.
We think Dan handled the sudden consecutive blends quite well. Afterwards it seemed to us that the blending had had an impact on Dan's anger. In short, we don't feel Dan has been the same since these incidents. The blends changed him for the better.
Jack and Quato. One of them was out one night walking home from work and the other tried to step in and take over, which almost always happens generously between alters in my system. Except something didn't work right. They realized they were both together, two individuals squished into one body. I can only describe the resulting combination "personality" as uproarious. Both are pranksters in their own way and together they kind of wanted to get into some trouble of some kind. Fortunately they didn't, but Quato couldn't get over his new half standard American, half hillbilly accent. The combination felt something like two close relatives or buddies who got a little tipsy and were laughing and stumbling around together, each with an arm around the other's shoulder.
Quato and Little John. Little John was in the body looking at some pretty things in a store window. Quato got drawn out by a desire to say something snarky to someone nearby. Suddenly, they were both together in the body. Quato laughed and continued laughing and laughing at the ticklishness of the experience until the body's laughter took on the aspect of a grimace. Quato cares about children but it's really not his strength. He's too dark and cynical and defers to those alters who are better with littles. When suddenly flooded with innocence and sweetness of Little John, well, it was really incongruous for Quato and not so pleasant after a while, yet he was still sort of laughing. It felt like lying down with a half dozen puppies jumping all over and around your face. Nice if you like that kind of thing, and most people would, but invasive and too sweet if you don't. The two could not unstick and after about fifteen minutes. Quato started wondering whether this was what dying of laughing sickness felt like. I took pity on him and was able to slip forward past both of them and take over.
John and Adam. Adam wanted to come into the body before a therapy session (coincidence? dunno) and he blended into me. I didn't feel quite as swamped like Dan or Jack did, but walking was difficult and every movement was slow. So opening up a box of candy proceeded as if done by something between the hands of a baby who has zero idea what to do and the hands of an adult who's done it thousands of times. It was slow, every movement was labored and deliberate, there was a little confusion at points but basically it happened. Once I arrived at therapy, Adam was still there but the thinking was just so slow and muddled and I felt so baby-like, I had to and was able to separate and pull in front.
Adam and Ashar do not vacate the body quickly in any case, so their presence tends to result in a blend-like experience. They often take several minutes to sort of fade back. This is particularly alarming with Ashar because he is very young and entirely mute. He literally never learned how to speak because he was abused by a mother's animal alter who didn't speak. It's nearly impossible for me to say anything or do even normal things like sign something. So if he lingers, the effect is debilitating. Yet I don't want to shove him out of the way because I do not want to do anything that is in any way abusive or dismissive. I want him to feel welcome no matter how it plays out.
Little John and Adam. Two littles. It had to happen eventually. Little John was very, very giggly because Adam felt so ticklish inside to him. Odd because Little John himself blended with anyone makes that older alter laugh. I guess it's their perspective. There was lots of giggling with the two blended, but the giggling was Little John's giggle. Adam was just being a baby and his presence made Little John feel what everyone else feels.
Blends force alters to get out of their comfort zone. They cause alters to know one another in a much more intimate way. They absolutely feel like a prelude to integration though that isn't their purpose as far as we know. Physical characteristics of the body -- gait, posture, accent -- seem to be halfway between the two alters out. Emotions seem affected but less blended. The thought patterns for most of the time retain their uniqueness.