CAPTCHA Challenge - Pick images/type distorted text from the image

Hi, We are using reCAPTCHA for our website. For some users the CAPTCHA challenge appear as to type the distorted text read from the image in the provided text box (as like attachment below). For some users the CAPTCHA challenge appear as to select the images from the list of images that resembles the provided image (as like attachment below) Question is - based on what condition the CAPTCHA challenge appears (for the type image). Is there a way to control the variations of CAPTCHA challenge (from the above listed 2 variations). Thanks in advance! -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.