Two movies below present demonstrations of mobile crowding -- crowding that is specific to the flanker that move with the target as opposed to flankers that surround the target in retinotopic coordinates. You will need a Quicktime plugin in your browser for these movies to play. If you do not have one, you can download one from <click here> Apple. Even with the right plugin, the movies do not match the quality of the experimental displays and, depending on many factors, may be severely degraded for your display. So if these do not play well on your browser or computer, my apologies. Another computer may play them better. Even if they do not play well, they should help show the arrangement of the displays even if they do not show exactly how they look. Other demonstrations of different tasks using this apparent motion technique (1. color-motion feature binding, 2. crowding (again, same as here), and 3. sequential binocular rivalry) can be found here.

For each movie, click on the start button at the lower left of the movie and click it again to stop before going on to the next movie.

In each of sixteen radial arms, a single target letter (3rd position) alternates with 4 flanking distractors (positions 1, 2, 4, and 5). While fixating the center dot and attending to one radial arm, the flickering target is flanked by flickering distractors. The task is to report whether the letter is normally oriented or left-right reversed. The target in each arm is different (randomly) but they all have the same orientation. In the fixed attention condition, the subject is asked to report the target orientation from the bottom position, but if any other target is noticed first, that is OK.

In the next display, a light sector encloses one radial arm at a time to guide attention from one arm to the next in synchrony with the target-distractor alternation. As a result, only the target is seen on each arm as it is selected in turn. If crowding is retinotopic, the target should be as degraded here as it is with fixed attention. If crowding is specific to the moving attention window, there should be less crowding since the moving window avoids the distractors. To make a fair comparison to the fixed attention case, the target array rotates with the guide so that the same target can be sampled successively during the trial (as is the case in the fixed attention). Fixate in the center and track the moving sector with attention.