Rotation of mental images by young and old college students: the effects of familiarity.
Younger and older college students judged whether letters, rotated from 0 to 180 degrees away from normal, upright position, were standard letters or mirror-images of standard letters. The analysis separated basic speed of response from the rate at which mental manipulations of the images of the letters took place. With letters from the English alphabet, younger (mean age, 21.6 years) and older (mean age 55.9 years) sugjects did not differ either in basic speed or in rate of manipulation. With unfamiliar, lower-case Greek letters, however, the basic speed of older subjects (mean age, 56.5 years) was slower than that of younger subjects (mean age, 21.2 years) while there was no difference in rate of manipulation. The results are inconsistent with an hypothesis of general slowing of central nervous system activity.