From Cognitive Agents to Cognitive Systems: Theoretical, Methodological, and Empirical Developments of van Gelder's (1998) "Dynamical Hypothesis".

Over two decades have passed since the publication of van Gelder's (1998) "dynamical hypothesis." In that paper, van Gelder proposed that cognitive agents were not digital computers-per the representational computational approach-but dynamical systems. The evolution of the dynamical hypothesis was driven by parallel advances in three areas.

Heavy-tailed distributions in haptic perception of wielded rods.

Humans identify properties (e.g., the length or weight) of objects through touch using somatosensory perceptions in the limbs.

The trajectory of thought: Heavy-tailed distributions in memory foraging promote efficiency.

Free-recall tasks suggest human memory foraging may follow a heavy-tailed distribution, such as a Lévy flight, patch foraging, or area-restricted search - walk procedures that are common in other activities of cognitive agents, such as food foraging in both animals and humans. To date, research merely equates memory foraging with hunting in the physical world based on similarities in statistical structure. The current work supports that memory foraging follows a heavy-tailed distribution by using categories with quantitative distances between each item: countries, which have physical distances, and animals, from which cognitive distances can be derived using a multidimensional scaling (MDS) procedure.

Does Attention Modify Contributions to Heaviness Perception?

The current study investigated the effect of attention on heaviness perception and its physiological and kinematic contributions. Participants lifted objects that varied in mass and volume while their muscle activity and movement were recorded. Participants were instructed to pay attention to their arm (internal) or the object (external).

Embodied Cognition in Performance: The Impact of Michael Chekhov's Acting Exercises on Affect and Height Perception.

Modern embodied approaches to cognitive science overlap with ideas long explored in theater. Performance coaches such as Michael Chekhov have emphasized proprioceptive awareness of movement as a path to attaining psychological states relevant for embodying characters and inhabiting fictional spaces. Yet, the psychology of performance remains scientifically understudied.

Lift speed moderates the effects of muscle activity on perceived heaviness.

Research has shown that perceived heaviness is a function of the ratio of muscle activity (measured by electromyogram [EMG]) to the resulting acceleration of the object. However, objects will commonly be lifted at different speeds, implying variation in both EMG and acceleration. This study examined the effects of lifting speed by having participants report perceived heaviness for objects lifted by elbow flexion at three different speeds: slow, preferred, and fast.

Evaluating the contributions of muscle activity and joint kinematics to weight perception across multiple joints.

Perceived heaviness is clearly a function of muscle activity: objects feel heavy, in part because they are lifted with more force than lighter feeling objects. Recent research showed that participants scale their perceptions to the ratio of muscle activity to lift acceleration during elbow lifts (Waddell et al. J Exp Psychol Hum Percept Perform 42:363-374, 2016).

Perceived heaviness in the context of Newton's Second Law: Combined effects of muscle activity and lifting kinematics.

Researchers generally agree that perceived heaviness is based on the actions associated with unsupported holding. Psychophysical research has supported this idea, as has psychophysiological research connecting muscle activity to the perceptions of heaviness and effort. However, the role of muscle activity in the context of the resulting motions has not been investigated.

Experimental control of scaling behavior: what is not fractal?

The list of psychological processes thought to exhibit fractal behavior is growing. Although some might argue that the seeming ubiquity of fractal patterns illustrates their significance, unchecked growth of that list jeopardizes their relevance. It is important to identify when a single behavior is and is not fractal in order to make meaningful conclusions about the processes underlying those patterns.

Emergent complexity matching in interpersonal coordination: Local dynamics and global variability.

Rhythmic coordination with stimuli and other people's movements containing variable or unpredictable fluctuations might involve distinct processes: detecting the fluctuation structure and tuning to or matching the structure's temporal complexity. This framework predicts that global tuning and local parameter adjustments (e.g.

The association between a single bout of moderate physical activity and executive function in young adults with Down syndrome: a preliminary study.

Background: This study was aimed at investigating the impact of a single exercise intervention on executive function in young adults with Down syndrome (DS).

Methods: Considering the relations among executive function, physical and mental health and early onset of Alzheimer's disease in this population, we tested three components of executive function (e.g.

Box shape influences the size-weight illusion during individual and team lifting.

Objective: The effects of box shape--specifically width and height--on the perception of heaviness were evaluated during individual and team lifting.

Background: Large objects are perceived to be as much as 50% lighter than smaller objects with the same mass. This size-weight illusion presents an obvious risk when lifting large and heavy boxes.

Manual coordination with intermittent targets: velocity information for prospective control.

Tracking a moving target requires that information concerning the current and future state of a target is available, allowing prospective control of the tracking effector. Eye movement research has shown that prospective visual tracking is achievable during conditions of both visible and occluded targets. The ability to track visually occluded targets has been interpreted as individuals integrating target velocity into eye movement motor plans.

Stabilizing perceptual-motor asymmetries during social coordination.

The current paper presents two studies that examine how we compensate for asymmetries during interpersonal coordination. It was predicted that destabilizing effects of asymmetries are offset through the recruitment and suppression of motor degrees-of-freedom (df). In Experiment 1, this effect was examined by having participants coordinate line movements of different orientations.

Congruency effects in interpersonal coordination.

Research on interpersonal coordination has demonstrated that incongruent tasks lead to unintended movements in the orthogonal plane. These effects have been interpreted using both an embodied simulation and coordination dynamics approach. To distinguish between these two perspectives, two experiments examined whether this congruency effect is best defined spatially or anatomically.

Interpersonal Fitts' law: when two perform as one.

Intra- and interpersonal coordination was investigated using a bimanual Fitts' law task. Participants tapped rhythmically between pairs of targets. Tapping was performed with one hand (unimanual), two hands (intrapersonal coordination), and one hand together with another participant (interpersonal coordination).

Motor imagery may incorporate trial-to-trial error.

The authors tested for 1/f noise in motor imagery (MI). Participants pointed and imagined pointing to a single target (Experiment 1), to targets of varied size (Experiment 2), and switched between pointing and grasping (Experiment 3). Experiment 1 showed comparable patterns of serial correlation in actual and imagined movement.

Target dimension affects 1/f noise in aiming.

The present study tested for 1/f noise to examine how timing and target constraints affect cognitive processes in aiming. Participants pointed to targets of varied height and width at preferred speed (Experiment 1) and as quickly as possible (Experiment 2). Results show greater intensity of 1/f noise, or long-range correlation in variability, at preferred speed and with increased accuracy demands perpendicular to the target (i.

Visual-spatial and anatomical constraints interact in a bimanual coordination task with transformed visual feedback.

There is a debate in the literature about the influence of spatial and anatomical constraints on bimanual coordination dynamics. In the present experiment, participants swung hand-held pendulums about the wrist while attending to visual feedback about relative phase (superimposed phase plots of each pendulum) that was displayed on a screen. Participants were instructed to maintain in-phase or anti-phase coordination in the visual display.

Sensory and perceptual interactions in weight perception.

In four experiments, a multidimensional signal detection analysis was used to determine the influence of length, diameter, and mass on haptically perceived heaviness with and without vision. This analysis allowed us to test for sensory and perceptual interactions between mass and size. As in previous research, sensory interactions were apparent in all four experiments.

Using 1/f noise to examine planning and control in a discrete aiming task.

The present study used 1/f noise to examine how spatial, physical, and timing constraints affect planning and control processes in aiming. Participants moved objects of different masses to different distances at preferred speed (Experiment 1) and as quickly as possible (Experiment 2). Power spectral density, standardized dispersion, rescaled range, and an autoregressive fractionally integrated moving average (ARFIMA) model selection procedure were used to quantify 1/f noise.

Peripheral neuropathy and object length perception by effortful (dynamic) touch: a case study.

The spatial extents of hand-held objects can be perceived nonvisually by wielding them. This ability of effortful or dynamic touch to exploit the mass moments of an object to perceive its length was evaluated with a 40-years old right-handed woman with surgically treated Arnold-Chiari Type 1 Malformation and cervical syrinx. At the time of the experiment she presented with loss of discriminative touch in the left arm but no comparable sensory deficits in the right arm or the lower extremities.

The effects of attention and handedness on coordination dynamics in a bimanual Fitts' law task.

Two experiments were conducted to investigate the effects of attention and handedness on bimanual coordination in the context of a dynamical model of coordinated movements. Participants performed a bimanual, rhythmic Fitts' law task in which the relative amount of attention directed to each task was manipulated by the relative difficulty associated with the pair of targets that each hand tapped. In both experiments, participants tended to lead with their preferred hand.

Psychophysical test for the independence of perception and action.

Research has suggested that perception and action are independent (see M. A. Goodale & A.

Symmetry and the devil.

F. Mechsner (2004) bases his argument for the primacy of perception on a simplified interpretation of phase transition findings. The authors show that attention to the details of phase transition analysis, as well as consideration of findings from steady-state experiments and the tools of symmetry theory, necessitate a theory of bimanual coordination that includes both perceptual and motor processes.