# Complexity Matching As Dyadic Property in Perceptual Crossing

Complexity matching into a minimal paradigm of movement-based social interaction aka joint action, Time-Series Analysis of Embodied Interaction: Movement Variability and Complexity Matching As Dyadic Properties. The task is also cool because artificial agents can be evolved to play the same game. The two participants move their objects on a loop by pushing a joystick left and right. They don’t see each other nor the screen. The only sensory modality is vibration. A vibration indicates to the participant when the sensor on her moving object intersects one of the objects, either the decoy or the other participant’s objects. The task is to click when you think you’re intersecting the other participant but not the static decoy. Presumably, the dyad can arrive at a pattern of movement that allows the two participants to feel each others’ presence simultaneously. In this paper we showed that complexity matching is involved in the process of playing this game. Go read the paper, Time-Series Analysis of Embodied Interaction: Movement Variability and Complexity Matching As Dyadic Properties.

# “Humanizing” of repetitive stimuli, and its relevance to gait cueing (aka rhythmic auditory stimulation)

Introduction: Rhythmic auditory cueing improves certain gait symptoms of Parkinson’s disease (PD). Cues are typically stimuli or beats with a fixed inter-beat interval. We show that isochronous cueing has an unwanted side-effect in that it exacerbates one of the motor symptoms characteristic of advanced PD. Whereas the parameters of the stride cycle of healthy walkers and early patients possess a persistent correlation in time, or long-range correlation (LRC), isochronous cueing renders stride-to-stride variability random. Random stride cycle variability is also associated with reduced gait stability and lack of flexibility.

Method: To investigate how to prevent patients from acquiring a random stride cycle pattern, we tested rhythmic cueing which mimics the properties of variability found in healthy gait (biological variability). PD patients (n=19) and age-matched healthy participants (n=19) walked with three rhythmic cueing stimuli: isochronous, with random variability, and with biological variability (LRC). Synchronization was not instructed.

Results: The persistent correlation in gait was preserved only with stimuli with biological variability, equally for patients and controls (p’s

Conclusion: Stimulus variability and patients’ propensity to synchronize play a critical role in fostering healthier gait dynamics during cueing. The beneficial effects of biological variability provide useful guidelines for improving existing cueing treatments.

Biologically-variable rhythmic auditory cues are superior to isochronous cues in fostering natural gait variability in Parkinson’s disease

# In joint action, scale-determined local coordination emerges on the background of multi-scale, power-law-like task performance.

In this experiment on minimal social cognition we found that local, scale-determined movement coordination was associated with successful joint action and emerged on the background of general multi-scale, power-law-like task performance. Time series analysis of embodied interaction:Movement variability and complexity matching as dyadic properties in Frontiers.

There is a growing consensus that a fuller understanding of social cognition depends on more systematic studies of real-time social interaction. Such studies require methods that can deal with the complex dynamics taking place at multiple interdependent temporal and spatial scales, spanning sub-personal, personal, and dyadic levels of analysis. We demonstrate the value of adopting an extended multi-scale approach by re-analyzing movement time-series generated in a study of embodied dyadic interaction in a minimal virtual reality environment (a perceptual crossing experiment). Reduced movement variability revealed an interdependence between social awareness and social coordination that cannot be accounted for by either subjective or objective factors alone: it picks out interactions in which subjective and objective conditions are convergent (i.e., elevated coordination is perceived as clearly social, and impaired coordination is perceived as socially ambiguous). This finding is consistent with the claim that interpersonal interaction can be partially constitutive of direct social perception. Clustering statistics (Allan Factor) of salient events revealed fractal scaling. Complexity matching defined as the similarity between these scaling laws was significantly more pronounced in pairs of participants as compared to surrogate dyads. This further highlights the multi-scale and distributed character of social interaction and extends previous complexity matching results from dyadic conversation to non-verbal social interaction dynamics. Trials with successful joint interaction were also associated with an increase in local coordination. Consequently, a local coordination pattern emerges on the background of complex dyadic interactions in the PCE task and makes joint successful performance possible.

Time series analysis of embodied interaction:Movement variability and complexity matching as dyadic properties

# The “nonlinear”, “dynamical” measures of gait are not just about the properties of an internal pace maker

Gait is not paced by a dedicated internal timing mechanism. Rather, its timing properties are a consequence of a complex dynamical exchange among the body, neural circuits, and the pattern of reaction forces determined by the environment. For this reason you have to be careful how variations in the setup could impact gait measures, and even make healthy walkers look like PD patients on a given metric. The more “nonlinear” and “dynamical” your measures of gait, the more you have to pay attention to the way they are influenced by the environmental constraints implicit in your setup.

Stride durations in gait exhibit long-range correlation (LRC) which tends to disappear with certain movement disorders. The loss of LRC has been hypothesized to result from a reduction of functional degrees of freedom of the neuromuscular apparatus. A consequence of this theory is that environmental constraints such as the ones induced during constant steering may also reduce LRC. Furthermore, obstacles may perturb control of the gait cycle and also reduce LRC. To test these predictions, seven healthy participants walked freely overground in three conditions: unconstrained, constrained (constant steering), and perturbed (frequent 90° turns). Both steering and sharp turning reduced LRC with the latter having a stronger effect. Competing theories explain LRC in gait by positing fractal CPGs or a biomechanical process of kinetic energy reuse. Mediation analysis showed that the effect of the experimental manipulation in the current experiment depends partly on a reduction in walking speed. This supports the biomechanical theory. We also found that the local Hurst exponent did not reflect the frequent changes of heading direction. This suggests that the recovery from the sharp turn perturbation, a kind of relaxation time, takes longer than the four to seven meters between successive turns in the present study.

The role of environmental constraints in walking: Effects of steering and sharp turns on gait dynamics

# An old review of theories dealing with how the environment and body could be constraining brain activity

Putting reins on the brain in Frontiers, part of the Radical Embodied Cognitive Neuroscience issue.

Radical embodied cognitive neuroscience (RECN) will probably rely on dynamical systems theory (DST) and complex systems theory for methods and formalism. Yet, there have been plenty of non-radical neurodynamicists out there for quite some time. How much of their work fits with radical embodied cognitive science, what do they need RECN for, and what are the inconsistencies between RECN and established neurodynamics that would have to be resolved? This paper is both theoretical hypothesis and review. First, it provides a brief overview of the typical, purely structural considerations why the central nervous systems (CNS) should be treated as a nonlinear dynamical system and what this entails. The reader will learn about the circular causality enclosing brain and behavior and different attempts to formalize this circularity. Then, three different attempts at linking dynamics and theory of brain function are described in more detail and criticized. A fourth method based on ecological psychology could fix some of the issues that the others encounter. It is argued that studying self-organization of the brain without taking its ecological embedding into account is insufficient. Finally, based on existing theoretical work we propose two roles that the CNS has to be fulfilling in order to allow an animal to behave adequately in its niche. In its first role the CNS has to be enslaved easily by patterns of behavior that guide the animal through its environment. In the second role the brain has to flexibly switch among patterns, what can be called the metastable circuit breaker. The relevance of this idea is supported using certain motor symptoms of Parkinson’s disease (PD). These symptoms can be explained as consequent to an excessive stability of the (metastable) circuit breaker.

Putting reins on the brain

# The Chua circuit sounds like this when its heart is broken. An exercise in SONIFICATION.

An exercise in sonification. This is what the Chua circuit looks like in one of its instantiations. As you can see, it is a heart split in two. Play the video to see it in action and hear it crying.

High-res video here: chua_heart_crying.avi.

# Van Gogh saw and painted one of physics’ unsolved problems-turbulence

Yet another instance of artists having a feel for and capturing in their work a natural phenomenon long before the scientists. Van Gogh managed to capture in these paintings a very tricky natural phenomenon:

According to this work by physicists from UNAM (ten years ago), Van Gogh “discovered” Kolmogorov’s equation $$P_R(\delta u_R)=\delta u_R/(\langle(\delta u_R)^2 \rangle)^{1/2}$$ which describes turbulent flow. Luminance differences in the painting correspond to velocity differences in fluid flow. What was he trying to achieve that led him to reproduce turbulence in an era when no one had a clue what it was and how to mimic it?

Why is turbulence so interesting? Turbulence contains structure where none is expected, and it contains lots of it. You blast a homogeneous fluid with nothing more than free energy and the fluid structures itself to dissipate the energy. You get structure for “free”. We are used to conversion between different types of energy, we study this in school. But the spontaneous conversion of energy to structure in turbulence is really weird. It is one of physics’ unsolved problems. Supposedly, Heisenberg (or H. Lamb) said the following on his deathbed, When I meet God, I am going to ask him two questions: Why relativity? And why turbulence? I really believe he will have an answer for the first.

Below is a link to a video explaining the same thing. Note, however, that they put too much emphasis on the eddies. You might be left with the impression that the turbulence in the paintings is contained in the spiraling light patterns. But it’s not about that at all. It would be too easy. The turbulence is everywhere in the paintings and this is what is so unique about them.

# Cespa vs. Cespa

Fun stuff! Follow a little discussion between Cespa and Cespa. I had to comment on the work of my own peers from Connecticut.

I had the chance (or misfortune?) to write a critical commentary of the work of my own people from CT. A special issue of Constructivist Foundations: Exploring the Diversity within Enactivism and Neurophenomenology gives a very comprehensive overview of modern developments in the field. Cespa was invited to contribute a paper or two and explain ecological psychology to the general audience. The fortress on the hill, as I called Cespa’s position, went for a dismissal of any apparent similarity between the Gibsonian approach and the sister field. What a surprise, this must have been the first time in history that Cespa tries to resolve an issue of theoretical convergence by making enemies! I think, however, that they made a few mistakes. So I explained the mistakes in my commentary. It amounts to a tiny little debate between classical Cespa and new Cespa. You can read my commentary Perception-Action Mutuality Does Not Obviate Emergence or the Animal’s Active Role in the Perceptual Act. You can get the whole book for free if you register with the journal: Constructivist Foundations: Exploring the Diversity within Enactivism and Neurophenomenology.

Many other interesting papers and opinions can be found in this issue, by both young and famed scholars. The list is actually impressive.

# Symmetry is not always nice. Here it is associated with certain dimensions of schizophrenia

Interestingly, schizophrenic patients exhibit more “veridical” perception when observing certain visual illusion displays from the gestalt kind, e.g. MIB. That is to say, patients’ perceptual apparatus doesn’t get captivated as much by the gestalt phenomenon. (‘Veridical’ and ‘illusion’ are very badly chosen words to describe gestalt effects. It implies a naive understanding of perception, the role of perception and the ontology of the world. But that’s another story. Some reading here: http://psychsciencenotes.blogspot.mx/2014/09/visual-illusions-and-direct-perception.html . Here I have to use ‘veridical’ and ‘illusion’ for communication purposes.)

Till Frank’s model-based analysis shows that an increased symmetry-breaking term explains the tendency of the healthy brain to get stuck in the Gestalt effect. Sometimes symmetry is not good. Symmetry in the way your brain works is not so beautiful nor healthy, unless you mean it in the sense of the movie A Beautiful Mind. What’s under this symmetry-breaking term is a more difficult question. For now we simply make the link between stability and a symmetry-breaking term.

Reported in “Self-Organization in Complex Systems: The Past, Present, and Future of Synergetics”, the proceedings of a conference dedicated to Hermann Haken,