If the author’s name is used in the text, only the date needs to be inside parentheses.
Duckworth (1986) discussed this.
When both the author and the date are used in the text, separate them with a comma.
In 1986, Duckworth argued…
If the author’s last name and the date both happen to appear in the text, there is no need to give further reference within the existing paragraph.
You need to include the year only once when referring to a particular study within a paragraph as long as the study will not be confused with other studies.
In her study of how individuals learn about density, Duckworth (1986) makes a critical case… Duckworth also found…
(American Psychological Association, 2010, pp. 88-89, 174)