What happened

Shares of BlackBerry (NYSE:BB) are soaring almost 10% higher in morning trading Wednesday while those of AMC Entertainment Holdings (NYSE:AMC) and GameStop (NYSE:GME) were falling 5% and 7%, respectively.

Only the video game retailer had any news to speak of that ought to affect its share price, and that was actually mildly positive.

People having a tug of war over a chasm

Image source: Getty Images.

So what

GameStop is being upgraded to the S&P 400 index beginning Aug. 4, replacing Weingarten Realty Investors, which is being acquired by Kimco Realty. Currently the video game company resides in the S&P 600 index, and when it's elevated it will be replaced by Lakeland Financial.

Typically stocks rise after being added to indexes because institutional investors that follow an index are required to buy the stock to match its performance. Since GameStop is moving from one index to another it is the equivalent of just rearranging the furniture, with an exchange traded fund or mutual fund selling GameStop shares in one index and buying it in another.

Now what

AMC started off the week on a tear, rising nearly 10% on Monday, but between yesterday's trading and today it has given back all of those gains.

BlackBerry is the curious mover here. Other than reporting yesterday its president and chief operating officer had an award of over 280,000 restricted stock units vest (for which he sold almost 110,000 shares to pay the taxes on the award), there was no news to speak of.

All three stocks were among the original meme stocks from the trading frenzy earlier this year and their shares will continue to rise and fall on a whim.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.