Ian S Howard

University of Plymouth | UoP · SECAM

Robotic manipulanda are extensively used in investigation of the motor control of human arm movements. They permit the application of translational forces to the arm based on its state and can be used to probe issues ranging from mechanisms of neural control to biomechanics. However, most current designs are optimized for studying either motor lear...

Pronunciation is an important part of speech acquisition, but little attention has been given to the mechanism or mechanisms by which it develops. Speech sound qualities, for example, have just been assumed to develop by simple imitation. In most accounts this is then assumed to be by acoustic matching, with the infant comparing his output to that...

Real-world tasks often require movements that depend on a previous action or on changes in the state of the world. Here we investigate whether motor memories encode the current action in a manner that depends on previous sensorimotor states. Human subjects performed trials in which they made movements in a randomly selected clockwise or countercloc...

In ball sports, we are taught to follow through, despite the inability of events after contact or release to influence the outcome [1, 2]. Here we show that the specific motor memory active at any given moment critically depends on the move-ment that will be made in the near future. We demonstrate that associating a different follow-through movemen...

In our daily life we often make complex actions comprised of linked movements, such as reaching for a cup of coffee and bringing it to our mouth to drink. Recent work has highlighted the role of such linked movements in the formation of independent motor memories, affecting the learning rate and ability to learn opposing force fields. In these stud...

Here we present the design and construction of a low-cost planar robotic arm that makes use of light weight component and a passive link mechanism to maintain fixed endpoint orientation. The arm structure itself is low-cost and built from carbon fiber tubes which yields a high stiffness to weight ratio. To facilitate construction, commercially avai...

Assessing levels of aggression–specifically reactive violence–has been a challenge in the past, since individuals might be reluctant to self-report aggressive tendencies. Furthermore, experimental studies often lack ecological validity. Immersive Virtual Reality (IVR) offers a reliable, ethically safe environment, and is the most realistic virtual...

Here we investigate variable-stiffness tendon drive for a robot arm. The novel aspect of our design is that it makes use of non-back-drivable worm-gear motor actuation, so static arm configurations can be maintained at a desired stiffness level without requiring motor power. We first analyze a link that is driven via uni-directional agonistic-antag...

Here we present the design for a compliant actuator than makes use of agonistic-antagonistic tendons. Its novelty lies in its use of worm-gear motor drive and industrial EtherCAT control. We first describe a test rig to investigate variable-stiffness tendon drive for a single link and the construction of a corresponding EtherCAT controller. The ten...

Here we describe the initial development of a 3D printed modular robotic segment that is driven by variable stiffness actuators (VSAs). The novelty of the presented work is the combination of cost-effective antagonist VSAs with mechanical modularity: this enables multiple segments to be used either as a stand-alone serpentine robot or as compliant...

Here we present the design for a compliant actuator than makes use of agonistic-antagonistic tendons. Its novelty lies in its use of worm-gear motor drive and industrial EtherCAT control. We first describe a test rig to investigate variable-stiffness tendon drive for a single link and the construction of a corresponding EtherCAT controller. The ten...

Here we investigate variable-stiffness tendon drive for a robot arm. The novel aspect of our design is that it makes use of non-back-drivable worm-gear motor actuation, so static arm configurations can be maintained at a desired stiffness level without requiring motor power. We first analyze a link that is driven via uni-directional agonistic-antag...

Automatic detection and preliminary classification of pathological speech signals into broad aetiological disorder categories would assist the clinical management of voice pathology. Recently much progress has been made using deep neural networks to accurately reconstruct EGG signal directly from the acoustic signal including from pathological spee...

The Time of Excitation (Tx) of speech, also widely known as the Glottal Closure Instants (GCI) denote the points in time at which the vocal folds close during the production of voiced speech. In this paper, we extend a previous approach based on a multilayer perceptron (MLP) using Echo State Networks (ESN), a variant of a Recurrent Neural Network (...

Current approaches to voice diagnosis involve a clinician examining the patient, listening to their voice and in some cases, using additional measurements of the larynx such as EGG. Here we train a feedforward convolutional neural network on a database of normal healthy drama students recorded speaking passages in English, to reconstruct the associ...

Here we extend previous work for the estimation of the time of excitation (Tx) from the speech signal using a shallow neural network. We make use of a dataset that consists of the simultaneously recorded speech and Laryngograph signals from drama students speaking a phonetically balanced passage. We first use the Laryngograph signal to estimate the...

Rationale Hypothetical moral dilemmas, pitting characteristically utilitarian and non-utilitarian outcomes against each other, have played a central role in investigations of moral decision-making. Preferences for utilitarian over non-utilitarian responses have been explained by two contrasting hypotheses; one implicating increased deliberative rea...

Here we describe a simple modular 3D-printed design for an inverted pendulum system that is driven using a stepper motor operated by a microcontroller. The design consists of a stainless-steel pole that acts as the pendulum, which is pivoted at one end and attached to a cart. Although in its inverted configuration the pendulum is unstable without s...

In our daily life we often make complex actions comprised of linked movements, such as reaching for a cup of coffee and bringing it to our mouth to drink. Recent work has highlighted the role of such linked movements in the formation of independent motor memories, affecting the learning rate and ability to learn opposing force fields. However, whil...

Human infants have a remarkable ability to learn to speak. To examine theories of some aspects of speech production development we previously developed Elija, a computational model of infant speech acquisition. Elija is an agent that can influence its environment by generating acoustic output by controlling an articulatory synthesizer as well as re...

Prior work has shown that independent motor memories of opposing dynamics can be learned when the movements are preceded by unique lead-in movements, each associated with a different direction of dynamics. Here we examine generalization effects using visual lead-in movements. Specifically, we test how variations in lead-in kinematics, in terms of d...

Here we consider the application of state feedback control to stabilise an articulatory speech synthesizer during the generation of speech utterances. We first describe the architecture of such an approach from a signal flow perspective. We explain that an internal model is needed for effective operation, which can be acquired during a babbling pha...

Recent advances in virtual technologies have allowed the investigation of simulated moral actions in aversive moral dilemmas. Previous studies have employed diverse populations to explore these actions, with little research considering the significance of occupation on moral decision-making. For the first time, in this study we have investigated si...

Advances in Virtual Reality (VR) technologies allow the investigation of simulated moral actions in visually immersive environments. Using a robotic manipulandum and an interactive sculpture, we now also incorporate realistic haptic feedback into virtual moral simulations. In two experiments, we found that participants responded with greater utilit...

Supplementary material for: Francis, K. B., Terbeck, S., Briazu, R. A., Haines, A., Gummerum, M., Ganis, G., & Howard, I. S. (2017). Simulating moral actions: An investigation of personal force in virtual moral dilemmas. Scientific reports, 7(1), 13954.

Rapid learning can be critical to ensure elite performance in a changing world or to recover basic movement after neural injuries. Recently it was shown that the variability of follow-through movements affects the rate of motor memory formation. Here we investigate if lead-in movement has a similar effect on learning rate. We hypothesized that both...

Here we present a robotic vocal apparatus incorporating a tongue body that is moved by stepper motors under computer control. The vocal tract consists of a central mouth region with a 2-dimentional tongue, a lip section and a nasal cavity. Movement of the articulators changes the vocal tract cross-sectional area, and thereby its acoustic properties...

[This corrects the article DOI: 10.1371/journal.pone.0164374.].

The nature of moral action versus moral judgment has been extensively debated in numerous disciplines. We introduce Virtual Reality (VR) moral paradigms examining the action individuals take in a high emotionally arousing, direct action-focused, moral scenario. In two studies involving qualitatively different populations, we found a greater endorse...

Visual observation of movement plays a key role in action. For example, tennis players have little time to react to the ball, but still need to prepare the appropriate stroke. Therefore, it might be useful to use visual information about the ball trajectory to recall a specific motor memory. Past visual observation of movement (as well as passive a...

Here we describe preliminary results in the construction of a mechanical vocal apparatus. The design employs an elliptical tongue of fixed radii and a linear jaw and lip section that move within a mouth cavity. The dimension and geometries of the articulators and mouth were found by fitting them to published human vocal tract data. The dataset used...

Humans are able to adapt their motor commands in order to make accurate movements in novel sensorimotor environments, such as when wielding tools that alter limb dynamics. However, it is unclear to what extent sensorimotor representations obtained through experience with one limb are available to the opposite, untrained limb, and in which form they...

Theories about the cognitive nature of phonological units have been constrained by the assumption that young children solve the correspondence problem for speech sounds by imitation, whether by an auditory-or gesture-based matching to target process. Imitation on the part of the child implies that he makes a comparison within one of these domains,...

In sports, the role of backswing is considered critical for generating a good shot, even though it plays no direct role in hitting the ball. We recently demonstrated the scientific basis of this phenomenon by showing that immediate past movement affects the learning and recall of motor memories. This effect occurred regardless of whether the past c...

Words are made up of speech sounds. Almost all accounts of child speech development assume that children learn the pronunciation of first language (L1) speech sounds by imitation, most claiming that the child performs some kind of auditory matching to the elements of ambient speech. However, there is evidence to support an alternative account and w...

Several studies have shown that sensory contextual cues can reduce the interference observed during learning opposing force fields. However, as each study examined a small set of cues often in a unique paradigm, the relative efficacy of different sensory contextual cues is unclear. Here we quantify how seven contextual cues, some investigated previ...

We describe a fully programmable Electrostatic Tactile (ET) feedback system that delivers a range of tactile textures to a mobile display. The ET system is a robust, thin, and optically transparent structure that can be overlaid unobtrusively on top of a display screen. The system exploits the phenomenon of electrovibration to create a controllable...

A recent study has found that toddlers do not compensate for an artificial alteration in a vowel they hear themselves producing. This raises questions about how young children learn speech sounds.

Supporting information and additional analyses, including seven figures (Figure S1 to Figure S7). (DOC)

Motor learning has been extensively studied using dynamic (force-field) perturbations. These induce movement errors that result in adaptive changes to the motor commands. Several state-space models have been developed to explain how trial-by-trial errors drive the progressive adaptation observed in such studies. These models have been applied to ad...

Rhythmic and discrete arm movements occur ubiquitously in everyday life, and there is a debate as to whether these two classes of movements arise from the same or different underlying neural mechanisms. Here we examine interference in a motor-learning paradigm to test whether rhythmic and discrete movements employ at least partially separate neural...

Imitation is almost always assumed to be the mechanism by which infants learn to pronounce speech sounds, which are the elements from which words are made up. Specifically, it is believed that auditory matching enables a child to reproduce speech sounds by copying those that he hears. For several reasons, we believe that this is not the way that th...

Imitation is almost always assumed to be the mechanism by which infants learn to pronounce speech sounds, which are the elements from which words are made up. Specifically, it is believed that auditory matching enables a child to reproduce speech sounds by copying those that he hears. For several reasons, we believe that this is not the way that th...

We describe the architecture and operation of Elija, a computational infant that learns to pronounce speech sounds. Elija is modelled as an agent who can interact with his environment but who has no a priori articulatory or perceptual knowledge of speech. His sensory system responds to touch and acoustic input. He judges the value of action and res...

In virtual assembly verification or remote maintenance tasks, bimanual haptic interfaces play a crucial role in successful task completion. This paper proposes a method for objectively comparing how well a haptic interface covers the reachable workspace of human arms. Two system configurations are analyzed for a recently introduced haptic device th...

In virtual assembly verification or remote maintenance tasks, bimanual haptic interfaces play a crucial role in successful task completion. This paper proposes a method for objectively comparing how well a haptic interface covers the reachable workspace of human arms. Two system configurations are analyzed for a recently introduced haptic device th...

Human subjects easily adapt to single dynamic or visuomotor perturbations. In contrast, when two opposing dynamic or visuomotor perturbations are presented sequentially, interference is often observed. We examined the effect of bimanual movement context on interference between opposing perturbations using pairs of contexts, in which the relative di...

Skillful tool use requires knowledge of the dynamic properties of tools in order to specify the mapping between applied force and tool motion. Importantly, this mapping depends on the orientation of the tool in the hand. Here we investigate the representation of dynamics during skillful manipulation of a tool that can be grasped at different orient...

Humans use their arms to engage in a wide variety of motor tasks during everyday life. However, little is known about the statistics of these natural arm movements. Studies of the sensory system have shown that the statistics of sensory inputs are key to determining sensory processing. We hypothesized that the statistics of natural everyday movemen...

Recent research into the acquisition of spoken language has stressed the importance of learning through embodied linguistic interaction with caregivers rather than through passive observation. However the necessity of interaction makes experimental work into the simulation of infant speech acquisition difficult because of the technical complexity o...

Children learn to speak during their first years of life and achieve a level of performance that current technology cannot match. The physical structure of the vocal apparatus aids the discovery of speech sounds and the natural interactions that occur between an infant and his caregiver play a pivotal role in his learning to understand and produce...

Our ability to skillfully manipulate an object often involves the motor system learning to compensate for the dynamics of the object. When the two arms learn to manipulate a single object they can act cooperatively, whereas when they manipulate separate objects they control each object independently. We examined how learning transfers between these...

Humans constantly use their hands to interact with the environment and they engage spontaneously in a wide variety of manual activities during everyday life. In contrast, laboratory-based studies of hand function have used a limited range of predefined tasks. The natural movements made by the hand during everyday life have thus received little atte...

We previously proposed a non-imitative account of learning to pronounce, implemented computationally using discovery and mirrored interaction with a caregiver. Our model used an infant vocal tract synthesizer and its articulators were driven by a simple motor system. During an initial phase, motor patterns develop that represent potentially useful...

Almost all theories of child speech development assume that an infant learns speech sounds by direct imitation, performing an acoustic matching of adult output to his own speech. Some theories also postulate an innate link between perception and production. We present a computer model which has no requirement for acoustic matching on the part of th...

The imitation of spoken stop consonants by an articulatory synthesizer using only general learning principles addresses significant issues in speech inversion and speech acquisition. Stop consonants are relatively large, complex acoustic events resulting from discrete articulations, so inversion based on the use of small time windows or based on th...

The goal of our current project is to build a system that can learn to imitate a version of a spoken utterance using an articulatory speech synthesiser. The approach is informed and inspired by knowledge of early infant speech development. Thus we expect our system to reproduce and exploit the utility of infant behaviours such as listening, vocal p...

Imitation is a powerful mechanism by which both animals and people can learn useful behavior, by copying the actions of others. We adopt this approach as a means to control an articulatory speech synthesizer. The goal of our project is to build a system that can learn to mimic speech using its own vocal tract. We approach this task by training an i...

Imitation is a powerful mechanism by which both animals and people can learn useful behavior, by copying the actions of others. We adopt this approach as a means to control an articulatory speech synthesizer. The goal of our project is to build a system that can learn to mimic speech using its own vocal tract. We approach this task by training an i...

Making choices is a fundamental aspect of human life. For over a century experimental economists have characterized the decisions people make based on the concept of a utility function. This function increases with increasing desirability of the outcome, and people are assumed to make decisions so as to maximize utility. When utility depends on sev...