"The problem so far with Koko is that her handler is the onliest person who seems to be able to understand her."

Not sure of what to make of that. I know that some animals can get very attached to certain individuals. In AK, our husky got attached to me. Poodle got attached to mom. My Lab got attached to me, my dad's to him.

Just picked up a Jack Russel from the animal shelter for the girls this past Saturday. It's the girls' dog, but so far she only comes when I call her. Probably she thinks this is a pack and I'm the leader of the pack. For whatever reason, though, she "performs" for me and not others. It's only been a few days and I'm sure things will evolve, but the trend is already set.

"Her utterances are usually two or three symbols, and just don't display much of anything in the way of syntax."
This, I think, is important. Positive reinforcement is a good thing, but it can be misleading. If the animal is getting continual praise for jabbering, then it will jabber. (OTOH, one would think a psychological researcher would be aware of this.)

"koko want banana"
"good girl koko, have a treat!"
"koko want banana"
"good girl koko, have a treat!"
"koko poopoo"
"good girl koko, have a treat!"
"koko poopoo banana"
"good girl koko, have a treat!"

You get the idea.

"... ASL-signing consultants who were brought in ... became more and more skeptical and finally disassociated themselves ... "
That's interesting - and reminiscent of other miraculous or amazing claims made in other venues. When a disinterested observer reads initial accounts from newspapers and so forth, the event sounds utterly amazing and convincing, but once a little research is done, the miracle tends to evaporate.

k