functions.php

<?php

// Remove the author box on single posts
remove_action( 'genesis_after_post', 'genesis_do_author_box_single' );

// Display author box on single posts
add_filter( 'get_the_author_genesis_author_box_single', '__return_true' );

// Display author box on archive pages
add_filter( 'get_the_author_genesis_author_box_archive', '__return_true' );

// Modify the author box title
add_filter( 'genesis_author_box_title', 'custom_author_box_title' );
function custom_author_box_title() {
	return '<strong>About the Author</strong>';
}

// Modify the size of the Gravatar in the author box
add_filter( 'genesis_author_box_gravatar_size', 'custom_author_box_gravatar_size' );
function custom_author_box_gravatar_size( $size ) {
	return 80;
}