What’s new and exciting about it? The paper demonstrates that a very common task which has been used countless times in biological motion research can be accomplished with high accuracy by a human observer without having to rely at all on the ability to recover the non-rigid structure of the articulated body of the depicted person.

The latter – the ability to recover the structure of the deforming body from the way it moves – has been the explicit subject of much research in the field. Different sorts of task have been used to accomplish that. In a particularly popular one, the observer is asked to indicate the direction (left or right) into which a stationary point-light walker is facing. We had shown before that this is possible to some degree with completely scrambled biological motion (Troje & Westhoff, 2006), but the comparatively low response accuracies nevertheless argued for a dominance of structural cues.

In this new study, we introduce a new kind of stimulus which is scrambled only to a degree necessary to deprive it from any horizontal asymmetry that could cue facing direction from structural information. As in the fully scrambled walker, the only hints to facing direction are in the local motion of individual trajectories. The difference between the new stimulus and the previously used ones is that we kept the vertical order of the individual dots intact. Specifically, the dots representing the feet are still on the ground and the ones representing the head it still at the top. While this change doesn’t add any information about facing direction in itself, it makes the information present in the stimulus much more accessible to the observer. It “validates” the directional cues contained in the particular movement of the feet.

A new interactive demo allows the user to play with the stimuli used in this experiment.

The paper is authored by Masahiro Hirai who spent two years as a postdoc in our lab and two former graduate students, Daniel Saunders and Dorita Chang, who both left for new positions in other labs after their recent graduation.

Dance your PhD 2011: A study of social interactivity using pigeon courtship from Emma Ware on Vimeo.

The good news first: Emma Ware successfully defended her PhD thesis on Friday. Congratulations! Emma had studied the dynamics of pigeon courtship behaviour as a means to understand the role of the partner’s responsiveness to ones own behaviour. She used a sophisticated tele-conferencing setup to manipulate the degree of “responsiveness” between two courting pigeons: The male and the female bird were located in two different rooms, but could see each other through a video interface. The same technology that a news moderator uses to read text on a screen while still looking straight into the camera was used to allow the bird to directly face the camera while still reading on the screen the behaviour of the other bird. In this situation, the birds court each other like if they were confronted with a real partner. Emma now manipulated both temporal and spatial contingencies in a way that would not be possible in the real world and used this technique to study the dynamics of interactivity between two socially interacting agents.

Now, Emma wasn’t the only one to finish her degree over the last little while. Dorita Chang defended her PhD thesis already last summer and moved on to a postdoc position in the lab of Andrew Welchman in Birmingham, UK. Daniel Saunders just submitted his PhD thesis and left for a new job at the Schepens Eye Research Institute in Boston. Masahiro Hirai, who has been working with us for two full years, moves on to a new job in his native Japan — at the Institute for Developmental Research in Kasugai. One of our 4th year thesis students defended her thesis today, another one will do the same next week.

So, the bad news is: We’ll lose a bunch of good people and we will be missing them all very much. The lab will change. Yes, there are new students, and they are doing well. But that isn’t the same. Some of the lab members who are leaving now had been working with me for six years. We work along and see each other almost on a daily basis. We get to know each other well as I see them developing from an inexperienced student into a serious scientist who will soon be supervising students on their own. So, after all, this isn’t really bad news.

I wish you all the best for your ongoing academic development, and that you will be successful in whatever you take on. The most important thing however is that you enjoy what you are doing. The privilege of our profession is that we can do what we like to do. But liking what we do is also the key to being a successful scientist. Becoming fully immersed with what we do is a privilege, but also a duty and necessity.

An another piece of good news: There is room for new graduate students and for new postdoctoral fellows. If you think you are a good fit for the Biomotion Lab, please send along your application.

Members of the Biomotion Lab at yesterday’s farewell BBQ party for our outgoing students