How to reduce recaptcha difficulty level

Question

Some of the captchas produced by reCAPTCHA are unreadable. Are there any configurations that we could use in order to lower difficulty level of reCAPTCHA (I'm using reCAPTCHA PHP API)

OR Are there any reCAPTCHA like services that doesn't use php gd library?

Answer 1

Google's Recaptcha has a Security Preference slider.