Suggestion for a group experiment:

Form a group of individuals to do the group soul experiment.
Group size (number of individuals) may be 6-12.
Share impressions without filtering and rationalizing.
Wait until you get an impression, do not force it, do not invent one.
Share what you get, unfiltered, without forming grammatically well-built sentences, keep out the rationalizing mind.

Theory of group consciousness and temporary group soul:
(brainstorming here)

Evolution of humanity went from collective consciousness to individualization and now next step is expanding to use group or collective consciousness and individual consciousness purposefully and selectively and consciously.

Individual consciousness and group consciousness:

There is a well-known story about a number of blind persons who touch an elephant and shall describe the thing they were touching. One says it is like a snake, one says it is like a tree, etc., because each one touched only a part of the body of the elephant.
Now if this group could share their impressions within a collective mind, they would get the whole picture.

Suggested terminology:

"group consciousness" may feel more like a technical term, "group soul" may feel more like what it feels like when experiencing it.

Example of experiences with a group consciousness / group soul experiment:

In 1999 i suggested this experiment to a group of ca. 10-12 spiritually interested individuals. The group was a local group of the Theosophical Society in Germany, the average age of the persons probably over 60.
We sat together around a big table. I gave these directions / "playing rules" for the experiment:
Don't speak in grammatically complete sentences.
Don't form rational sentences.
Do speak spontaneously and only when you get a feeling / an impression.
Don't think.
Only speak when words come up spontaneously.

How it went:

We did this, it went well, everyone "behaved" well, that is, we managed to keep out rational thinking and ego, and spoke in "picturesque language", like in "free association".

The experience:

My personal experience of it:
We seemed to get more and more in sync, speaking about the same thing, having a common feeling or vision of something of which we received impressions which we spoke out then. The feeling and/or power and/or clarity of the vision increased more and more.

The experiences of other participants:
After the experiment, I asked others what they had felt, what their overall impression of the experiment was, and they described similar impressions and experiences.

The outcome of the experiment:
Not much. Everyone found it to be an interesting experience, but no one was intersted to do it again.