herp derp
this is the right way:
$args = array(
'post_type' => 'publication',
'tax_query' => array(
array(
'taxonomy' => 'category',
'field' => 'slug',
'terms' => 'acciss-study',
),
array(
'taxonomy' => 'type',
'field' => 'slug',
'terms' => 'press-releases-statements',
),
),
);
$the_query = new WP_Query( $args );