Laravel: get name from table users

I need get the name field in user table

My method in the controller:

public function reviewsactivity()
{
    $activity = Activity::orderBy('id', 'DESC')->paginate();
    $users = User::orderBy('id', 'ASC')->pluck('id', 'name');
    return view('reviews.reviewsactivity', compact('activity', 'users'));
}

And the view:

              @foreach($activity as $actividad)
                  <tr>
                      <td>{{ $actividad->description }}</td>
                      <td>{{ $actividad->subject_type }}</td>
                      <td>{{ $actividad->user->name }}</td>
                      <td>{{ $actividad->causer_type }}</td>
                      <td>{{ date('d-m-Y', strtotime($actividad->created_at)) }}</td>
                  </tr>
              @endforeach

The field in the Activity table: causer_id

And I have the next log:

 Trying to get property of non-object 
 (View: C:\laragon\www\tao\resources\views\reviews\reviewsactivity.blade.php)

Assuming you have user_id in activities table referencing users table then you can define belongsTo relationship in Activity model

Activity Model

public function user(){
     return $this->belongsTo(User::class, 'user_id');
}

Now Fetch Activity with eager loading using with('user')

public function reviewsactivity()
{
    $activity = Activity::with('user')->orderBy('id', 'DESC')->paginate();
    $users = User::orderBy('id', 'ASC')->pluck('id', 'name');
    return view('reviews.reviewsactivity', compact('activity', 'users'));
}

Check Eager Loading documents here https://laravel.com/docs/5.6/eloquent-relationships#eager-loading