如何在Laravel资源控制器中使用子模型返回belongsTo模型的一个属性

I'm using Laravel as a REST API for a SPA. I have a relationship where families have multiple contributions. The contributions table has a foreign key reference to family's id. I can call on the contributions route with the hasMany/belongsTo set up, and every contribution gets the entire family model it belongs to. But I don't need all that data, I just need a single field from the family table (not the id, but a different field) with each contribution.

Here are my models and resource controller:

class Family extends Eloquent {

    protected $table = 'families';

    // relationships
    public function contributions() {
        return $this->hasMany('Contribution');
    }
}

class Contribution extends Eloquent {

    protected $table = 'contributions';

    // relationships
    public function family() {
        return $this->belongsTo('Family');
    }

    public function other_field() {
        return $this->belongsTo('Family')->select('other_field');
    }   
}

class ContributionController extends BaseController {

    public function index()
    {
        // works - but returns the entire family with every contribution
        $contributions = Contribution::with('family')->get();

        // returns other_field == null with every contribution
        $contributions = Contribution::with('other_field')->get();

        return Response::json($contributions->toArray(),
            200);
    }

Where am I going wrong with selecting this single field from the belongsTo relationship?

You can use query constraints on the relationship if you use eager loading.

Family::with(['contributions', function($query)
{
    $query->select('column');
}])->get();