The easiest thing to do is to run a malware detector program on your computer to rule out the possibility -- first -- that it just isn't your computer.

MacScan offers a 30-day free trial of their software (which is legitimate) here:

http://macscan.securemac.com/

Windows offers a free virus/malware scanner here:

http://www.microsoft.com/security/sc...s/default.aspx

There are, of course, dozens of others available for Windows.

Regardless of what other people's experiences are, you should also contact Psychology Today to inform them of what you're experiencing. The fact that it's only happening on their site may suggest something is going on with their site or an ad they are running through their ad network. Here's their contact page:

https://my.psychologytoday.com/feedback

Although I don't know if this email address will work, you can also try emailing them at:

aaron@psychologytoday.com

Best,
DocJohn