Final answer:
McConkie and Rayner's study found that reading comprehension remains relatively normal with twenty spaces of text visible around the fixation point, aligning with psychological concepts of visual acuity and short-term memory capacity. The correct option in the final part of your specific question is "a. Twenty; around".
Step-by-step explanation:
McConkie and Rayner researched to understand how individuals process text when reading on a computer screen with a limited amount of text around the fixation point. They discovered that reading speed and comprehension remained relatively normal as long as approximately twenty spaces of text were visible, centered around the fixation point. This finding is significant as it suggests our short-term memory capacity can adapt to and effectively process information even when our visual field is constricted.
This notion aligns with the understanding of visual acuity as exemplified by the Snellen chart and the ability of individuals to read text from specific distances, despite the limitation in text visibility. Therefore, the correct option in the final part of your specific question is "a. Twenty; around".