how to keep next and prev links in specific category

When I click on a specific category and cycle through the next and previous links, posts excerpts are displayed within that specific category. Which is great.
e.g. https://webzine.thesocialedge.com/category/articles/

However, when viewing a specific post and cycling through via the next and previous links, the posts displayed are from every category. How do I make the posts displayed from a post page stay within the particular post category?
e.g.https://webzine.thesocialedge.com/arts-culture/hg-wells-at-the-movies/

Code appearing on index.php and single.php pages is:
/ <div class=”navigation”>
<div class=”alignleft”><?php previous_post_link(‘« %link’) ?></div>
<div class=”alignright”><?php next_post_link(‘%link »’) ?></div>
</div> /

Where do I go to make the changes so that cycling through posts stay in the same category as in the first para above, rather than every post?

Thanks for any help.
Peter

P.S. Not a programmer but can search, copy, paste, and manipulate!