Problem with admin columns

The title is showing but the content is empty.. I tried following few tutorials time after time but i guess i miss something.. How can i get it to echo 'test' on each col please?

// ADD NEW COLUMN
function pslider_columns_head($defaults) {
    $defaults['show_on_page'] = 'Shown on page';
    return $defaults;
}

// SHOW THE VALUE
function pslider_columns_content($column_name, $post_ID) {
    if ($column_name == 'show_on_page') {
        echo 'test';
    }
}

add_filter('manage_posts_columns', 'pslider_columns_head');
add_action('manage_posts_custom_column', 'pslider_columns_content', 10, 2);