Robert W. Isenhower

Dynamics of representational change: entropy, action, and cognition.

Explaining how the cognitive system can create new structures has been a major challenge for cognitive science. Self-organization from the theory of nonlinear dynamics offers an account of this remarkable phenomenon. Two studies provide an initial test of the hypothesis that the emergence of new cognitive structure follows the same universal principles as emergence in other domains (e.g., fluids, lasers). In both studies, participants initially solved gear-system problems by manually tracing the force across a system of gears. Subsequently, they discovered that the gears form an alternating sequence, thereby demonstrating a new cognitive structure. In both studies, dynamical analyses of action during problem solving predicted the spontaneous emergence of the new cognitive structure. Study 1 showed that a peak in entropy, followed by negentropy, key indicators of self-organization, predicted discovery of alternation. Study 2 replicated these effects, and showed that increasing environmental entropy accelerated discovery, a classic prediction from dynamics. Additional analyses based on the relationship between phase transitions and power-law behavior provide converging evidence. The studies provide an initial demonstration of the emergence of cognitive structure through self-organization.

Autism and social disconnection in interpersonal rocking.

Individuals with autism spectrum disorders (ASDs) have significant visuomotor processing deficits, atypical motoric behavior, and often substantial problems connecting socially. We suggest that the perceptual, attentional, and adaptive timing deficiencies associated with autism might directly impact the ability to become a socially connected unit with others. Using a rocking chair paradigm previously employed with typical adults, we demonstrate that typically-developing (TD) children exhibit spontaneous social rocking with their caregivers. In contrast, children diagnosed with ASD do not demonstrate a tendency to rock in a symmetrical state with their parents. We argue that the movement of our bodies is one of the fundamental ways by which we connect with our environment and, especially, ground ourselves in social environments. Deficiencies in perceiving and responding to the rhythms of the world may have serious consequences for the ability to become adequately embedded in a social context.

Direct Learning in Dynamic Touch

A dynamic touch paradigm in which participants judged the lengths of rods and pipes was used to test the D. M. Jacobs and C. F. Michaels (2007) theory of perceptual learning. The theory portrays perception as the exploitation of a locus on an information manifold and learning as continuous movement across that manifold to a new locus, as guided by information available in feedback. The information manifold was defined as a 1-dimensional space of inertial variables. To encourage maximal learning, a 2-step procedure was used in each of 2 experiments. Each step comprised a pretest to identify the starting locus on the information manifold, a practice phase in which feedback specifying the optimal locus was given, and a posttest in which the ending locus on the manifold was identified. In the 2nd step, a different feedback variable specified a different optimum. In both experiments, participants, who sometimes began at different loci, showed the predicted movement toward the optimum in each phase. Whereas previous applications of the theory posit the existence of information-for-learning without identifying a candidate variable, such a candidate is identified.

Effects of intention and learning on attention to information in dynamic touch.

The current research distinguishes two types of attention shifts: those entailed by perceptual learning and those entailed by changing intention. In perceptual learning, participants given feedback have been shown to gradually shift attention toward the optimal (i.e., specifying) information variable for the task. A shift in variable use is also expected when intention changes, because an intention to perceive some property entails attunement to information about that property. We compared the effects of feedback and intention in a dynamic (kinesthetic) touch task by representing both as changes of locus in an information space of inertial variables. Participants wielded variously sized, unseen, rectangular parallelepipeds and made length or width judgments about them. When given feedback, participants made gradual attentional shifts toward the optimal variable, which demonstrates the education of attention. When asked to report a new property, participants made large attentional jumps to the ballpark of the optimal variable for the new property. Exploratory movements were measured on 6 participants and were found to differ as a function of intention and to change with learning.

Affording cooperation: Embodied constraints, dynamics, and action-scaled invariance in joint lifting

Understanding the physical and interpersonal constraints that afford cooperation during real-world tasks requires consideration of the fit between the environment and task-relevant dimensions of coactors and the coactors’ fit with each other. In the present study, we examined how cooperation can emerge during ongoing interaction using the simple task of two actors’ moving long wooden planks. The system dynamics showed hysteresis: A past-action mode persisted when both solo and joint actions were possible. Moreover, pairs whose arm spans were both short, both long, or mismatched made action-mode transitions at similar points, when scaled by a relational measure. The relational measure of plank length to arm span was dictated by the pair member with the shorter arm span, who, thus, had a greater need to cooperate during the task. The results suggest that understanding affordances for cooperation requires giving more consideration to constraints imposed by the fit between coactors’ action capabilities.

Human odometer is gait-symmetry specific

In 1709, Berkeley hypothesized of the human that distance is measurable by ‘the motion of his body, which is perceivable by touch’. To be sufficiently general and reliable, Berkeleys hypothesis must imply that distance measured by legged locomotion approximates actual distance, with the measure invariant to gait, speed and number of steps. We studied blindfolded human participants in a task in which they travelled by legged locomotion from a fixed starting point A to a variable terminus B, and then reproduced, by legged locomotion from B, the A–B distance. The outbound (‘measure’) and return (‘report’) gait could be the same or different, with similar or dissimilar step sizes and step frequencies. In five experiments we manipulated bipedal gait according to the primary versus secondary distinction revealed in symmetry group analyses of locomotion patterns. Berkeleys hypothesis held only when the measure and report gaits were of the same symmetry class, indicating that idiothetic distance measurement is gait-symmetry specific. Results suggest that human odometry (and perhaps animal odometry more generally) entails variables that encompass the limbs in coordination, such as global phase, and not variables at the level of the single limb, such as step length and step number, as traditionally assumed.

Information space is action space: perceiving the partial lengths of rods rotated on an axle

In a single experiment, perceivers held unseen rods at some position along their lengths and reported the two partial lengths—to the left and to the right of the hand. Wielding was mechanically limited to a vertical plane. Previous research suggested that the information exploited for this task is captured in a space created from the moment of inertia and gravitational torque. The experiment reported here attempted to replicate the relevance of that space and to ask how exploration might access it. Perceivers were given feedback on accuracy on Blocks 2 and 3 of a four-block experiment, and their performance and position in information space were monitored. Exploratory movements were recorded. Judgments were shown to depend on inertial and gravitational torques, as expected. Analysis of exploratory movements suggested that occupying a locus in information space is equivalent to exploring at some angular acceleration. The apparent weighting of cues (gravitational and inertial torque), which might be interpreted as a cognitive process, was instead interpreted as a consequence of manner of exploration.

Perceiving Action-Relevant Properties of Tools Through Dynamic Touch: Effects of Mass Distribution, Exploration Style, and Intention

At issue in the present series of experiments was the ability to prospectively perceive the action-relevant properties of hand-held tools by means of dynamic touch. In Experiment 1, participants judged object move-ability. In Experiment 2, participants judged how difficult an object would be to hold if held horizontally, and in Experiments 3 and 4, participants rated how fast objects could be rotated. In each experiment, the first and second moments of mass distribution of the objects were systematically varied. Manipulations of wielding speed and orientation during restricted exploration revealed perception to be constrained by (a) the moments of mass distribution of the hand-tool system, (b) the qualities of exploratory wielding movements, and (c) the intention to perceive each specific property. The results are considered in the context of the ecological theory of dynamic touch. Implications for accounts of the informational basis of dynamic touch and for the development of a theory of haptically perceiving the affordance properties of tools are discussed.

Equivalence of Human Odometry by Walk and Run Is Indifferent to Self-Selected Speed

ABSTRACT Humans and other animals can measure distances nonvisually by legged locomotion. Experiments typically employ an outbound measure (M) and an inbound report (R) phase. Previous research has found distance reproduction to be maximally accurate, when gait symmetry and speed of M and R are of like kind: Successful human odometry manifests at the level of the M-R system. In the present work, M was an experimenter-set distance produced by a blindfolded participant using a primary gait (walk, run). R was always by walk. Fast and slow versions of walk and run were adopted by participants, such that when M was fast R was slow, and vice versa. Distance was underestimated when M was slower than R and overestimated when M was faster than R. However, the pattern of participant-adopted velocities indicated that it was the instructions, not the speed as such, that yielded the pattern of results. The results are interpretable through a dynamical perspective and indicate speed is an imperfection parameter acting on the attractors of the M-R system.