John G. Holden

Self-Organization of Cognitive Performance

Background noise is the irregular variation across repeated measurements of human performance. Background noise remains after task and treatment effects are minimized. Background noise refers to intrinsic sources of variability, the intrinsic dynamics of mind and body, and the internal workings of a living being. Two experiments demonstrate 1/f scaling (pink noise) in simple reaction times and speeded word naming times, which round out a catalog of laboratory task demonstrations that background noise is pink noise. Ubiquitous pink noise suggests processes of mind and body that change each others dynamics. Such interaction-dominant dynamics are found in systems that self-organize their behavior. Self-organization provides an unconventional perspective on cognition, but this perspective closely parallels a contemporary interdisciplinary view of living systems.

A fractal approach to dynamic inference and distribution analysis

Event-distributions inform scientists about the variability and dispersion of repeated measurements. This dispersion can be understood from a complex systems perspective, and quantified in terms of fractal geometry. The key premise is that a distributions shape reveals information about the governing dynamics of the system that gave rise to the distribution. Two categories of characteristic dynamics are distinguished: additive systems governed by component-dominant dynamics and multiplicative or interdependent systems governed by interaction-dominant dynamics. A logic by which systems governed by interaction-dominant dynamics are expected to yield mixtures of lognormal and inverse power-law samples is discussed. These mixtures are described by a so-called cocktail model of response times derived from human cognitive performances. The overarching goals of this article are twofold: First, to offer readers an introduction to this theoretical perspective and second, to offer an overview of the related statistical methods.

Scaling laws in cognitive sciences

Scaling laws are ubiquitous in nature, and they pervade neural, behavioral and linguistic activities. A scaling law suggests the existence of processes or patterns that are repeated across scales of analysis. Although the variables that express a scaling law can vary from one type of activity to the next, the recurrence of scaling laws across so many different systems has prompted a search for unifying principles. In biological systems, scaling laws can reflect adaptive processes of various types and are often linked to complex systems poised near critical points. The same is true for perception, memory, language and other cognitive phenomena. Findings of scaling laws in cognitive science are indicative of scaling invariance in cognitive mechanisms and multiplicative interactions among interdependent components of cognition.

Human Cognition and 1/f Scaling

Ubiquitous 1/f scaling in human cognition and physiology suggests a mind-body interaction that contradicts commonly held assumptions. The intrinsic dynamics of psychological phenomena are interaction dominant (rather than component dominant), and the origin of purposive behavior lies with a general principle of self-organization (rather than a special neurocognitive mechanism). E.-J. Wagenmakers, S. Farrell, and R. Ratcliff (2005) raised concerns about the kinds of data and analyses that support generic 1/f scaling. This reply is a defense that furthermore questions the model that Wagenmakers and colleagues endorse and their strategy for addressing complexity.

The Emergent Coordination of Cognitive Function.

1/f scaling has been observed throughout human physiology and behavior, but its origins and meaning remain a matter of debate. Some argue that it is a byproduct of ongoing processes in the brain or body and therefore of limited relevance to psychological theory. Others argue that 1/f scaling reflects a fundamental aspect of all physiological and cognitive functions, namely, that they emerge in the balance of independent versus interdependent component activities. In 4 experiments, series of key-press responses were used to test between these 2 alternative explanations. The critical design feature was to take 2 measures of each key-press response: reaction time and key-contact duration. These measures resulted in 2 parallel series of intrinsic fluctuations for each series of key-press responses. Intrinsic fluctuations exhibited 1/f scaling in both reaction times and key-contact durations, yet the 2 measures were uncorrelated with each other and separately perturbable. These and other findings indicate that 1/f scaling is too pervasive to be idiosyncratic and of limited relevance. It is instead argued that 1/f scaling reflects the coordinative, metastable basis of cognitive function.

Dispersion of Response Times Reveals Cognitive Dynamics

Trial-to-trial variation in word-pronunciation times exhibits 1/f scaling. One explanation is that human performances are consequent on multiplicative interactions among interdependent processes-interaction dominant dynamics. This article describes simulated distributions of pronunciation times in a further test for multiplicative interactions and interdependence. Individual participant distributions of approximately 1,100 word-pronunciation times were successfully mimicked for each participant in combinations of lognormal and power-law behavior. Successful hazard function simulations generalized these results to establish interaction dominant dynamics, in contrast with component dominant dynamics, as a likely mechanism for cognitive activity.

The Reality of Experience: Gibson's Way

This paper considers some first principles that might provide a basis for an objective science of experience (presence or immersion). Dimensions that are considered include classical Newtonian measures of the distal stimulus, changes in neural mechanisms reflecting the proximal stimulus, information theoretic measures of the statistical properties of events, and functional properties related to intentions and abilities. Gibsons ecological framework is suggested as a promising functional approach for defining the reality of experience in relation to the problem of designing virtual environments. This approach emphasizes the tight coordination between perception and action and fixes the measurement coordinate system relative to the capacity for action.

Intentional Contents and Self-Control

Conventional research programs adopt efficient cause as a metaphor for how mental events affect behavior. Such theory-constitutive metaphors usefully restrict the purview of research programs, to define the space of possibilities. However, conventional research programs have not yet offered a plausible account of how intentional contents control action, and such an account may be beyond the range of its theoretical possibilities. Circular causality supplies a more inclusive metaphor for how mental events might control behavior. Circular causality perpetuates dynamic structures in time. Mental contents are seen as emergent dynamic constraints perpetuated in time and vertically coupled across their multiple timescales. Intentional contents are accommodated as extraordinary boundary conditions (constraints) that evolve on timescales longer than those of motor coordination (Kugler & Turvey, 1987). Intentional contents, on their longer timescales, are thus available to control embodied processes on shorter timescales. One key assumption-that constraints are vertically coupled in time-is motivated empirically by correlated noise, long-range correlations in the background variability of measured laboratory performances.

Fractal 1/f Dynamics Suggest Entanglement of Measurement and Human Performance

Variability of repeated measurements in human performances exhibits fractal 1/ƒ noise. Yet the relative strength of this fractal pattern varies widely across conditions, tasks, and individuals. Four experiments illustrate how subtle details of the conditions of measurement change the fractal patterns observed across task conditions. The results call into question whether measurement noise and measured signal can be distinguished in human performance, suggesting that human performance is inextricably entangled with measurement context. Perhaps, though, a hypothesis of soft assembly of human performance can circumvent the conundrum (e.g., Turvey, 2007).

Perceptual-Motor Coordination in an Endoscopic Surgery Simulation

AbstractBackground: This study examined perceptual-motor coordination with an apparatus that simulated a situation representative of endoscopic surgery. Methods: Participants were trained with one arrangement of the apparatus, then tested with an alternative arrangement in which either the positions of the camera, the surgeon, or the objects in the surgical field were altered. Results: Results showed that changes of either the cameras position or the surgeons position disrupted performance. However, when the camera and surgeon positions were changed together, skilled performance was maintained. Conclusions: This suggests that skill depends on a consistent mapping between the virtual hands and eyes, but not on the particular visual or motor orientations. The results suggest that movements of the camera during surgery can disrupt coordinated action. Also, in the design of training simulators, the mapping between camera and instruments may be more important than the static appearance of the displays or the topology of the movements.