Alen Hajnal

University of Southern Mississippi, Psychology, Faculty Member

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Steven Pinker

Harvard University

Krishna Prasad Miyapuram

Indian Institute of Technology Gandhinagar

David Pierre Leibovitz

Carleton University

David Seamon

Kansas State University

Amir Manbachi

Johns Hopkins University

John Johnson

Pennsylvania State University

Matthew Ratcliffe

University of York

Adam M Croom

Case Western Reserve University

John Sutton

Macquarie University

Raoul Bongers

University of Groningen

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Papers by Alen Hajnal

Functional Specificity in Perception by Means of a Wielded Object

PsycEXTRA Dataset, 2013

Functional organization of the haptic perceptual system: Transfer of attunement and calibration

PsycEXTRA Dataset, 2006

ABSTRACT A model of the functional organization of perception-action systems was proposed using c... more ABSTRACT A model of the functional organization of perception-action systems was proposed using conceptual tools from group theory. More specifically, an attempt was made to test whether various configurations of perception-action units are organized as functional equivalence classes. The dynamic touch paradigm of perceiving spatial extent by wielding unseen objects was used to investigate the functional organization of the haptic perceptual system. The defining characteristics of equivalence classes (reflexivity, symmetry and transitivity) were empirically assessed using transfer of calibration as a measure of the connection between units. Reflexivity was measured by recalibration of length perception using trained effectors or objects; symmetry was assessed by the amount of calibration transfer of length perception by hand to length perception by foot, and vice versa, and by transfer of calibration from perceived rigid object (e.g., rod) length to perceived non-rigid object (e.g., rope) length, and vice versa; transitivity involved a battery of such tests among three objects: rods, ropes and whips (partially rigid objects). The successes, failures and implications of the group-theoretic model of functional organization were discussed.

Do Geographical Slants Feel Steeper Than They Look?

by Alen Hajnal and D. Bunch

Journal of Vision, 2014

Task specificity and anatomical independence in perception of properties by means of a wielded object

Journal of experimental psychology. Human perception and performance, 2014

Behavior is typically organized with respect to a goal to be achieved rather than the anatomical ... more Behavior is typically organized with respect to a goal to be achieved rather than the anatomical components used in doing so. Similarly, perception is typically organized with respect to a property to be perceived rather than the anatomical components used in doing so. Such task specificity and anatomical independence is manifest in perception of properties of a wielded object. In 6 experiments, we investigated whether these properties might also be manifest in perception of properties by means of a wielded object. In particular, we investigated perception of whether a surface could be stood on when the object used to explore that surface is wielded by the preferred and nonpreferred hands (Experiment 1), by 1 or both hands (Experiment 2), by different 2-handed grips (Experiment 3), and by entirely different limbs (i.e., the hand and the foot, Experiments 4-6). In general, the results show that perception reflected the action capabilities of the perceiver but was largely unaffected b...

Getting off on the right (or left) foot: perceiving by means of a rod attached to the preferred or non-preferred foot

Experimental brain research, 2014

Behavior is typically organized in terms of a goal one intends to achieve rather than in terms of... more Behavior is typically organized in terms of a goal one intends to achieve rather than in terms of the anatomical components used in doing so. Similarly, perceptual behavior is typically organized in terms of a property one intends to perceive rather than in terms of the anatomical components used in doing so. Such task-specificity and anatomical independence are manifest in perception of properties of wielded objects. We investigated whether these properties are also manifest in perception of properties by means of wielded objects. Blindfolded participants explored an inclined surface with a rod attached to their preferred or non-preferred foot and reported whether they would be able to stand on that surface. Perception reflected action capabilities, but was unaffected by foot used, highlighting the haptic system as a smart perceptual device.

INFLUENCE OF GROUND SURFACE ON SLANT PERCEPTION

by Alen Hajnal and D. Bunch

Loudness threshold as a function of sound source location using circum-aural headphones in noisy and sound-proof acoustic environments

Fractal Dynamics of Visual Search as a Function of the Gestalt Law of Proximity

Optical Push by Geographical Slant Affects Postural Sway

by Alen Hajnal, John Shelley-Tremblay, and Deanna Rumble

Ecological Psychology, 2014

ABSTRACT This study shows that perceived geographical slant affects postural stability. In 2 expe... more ABSTRACT This study shows that perceived geographical slant affects postural stability. In 2 experimental conditions participants stood on a force platform that measured center of pressure (COP) during quiet stance while looking at a rigid, flat ramp surface of varying geographical slants. Using an otherwise identical procedure, participants in the second condition also provided verbal estimates of the steepness of the surface in degrees. Several measures of postural stability offered converging evidence that COP sway gradually increased as geographical slant decreased to 0 (horizontal ground). Specifically, COP was sensitive to changes in surface slant. Both the range and the standard deviation of COP showed the same trend of increased variability with decreasing geographical slant angles in both conditions. The area of the ellipse covering COP sway (based on a principal components analysis) showed the same tendency: ellipse area got larger for smaller, more horizontal slants. Nonlinear fractal dynamics of COP sway, as measured by the Hurst exponent of COP, pointed in the same direction: more fractal patterns, known to be correlated with increased muscle activity and decline in postural stability, were measured for shallower surface slants. There were no effects of verbal estimates on any of the measures, suggesting that explicit awareness of slant does not bias postural stability above and beyond the effects of visual environment.

A Proposed Treatment for Visual Field Loss caused by Traumatic Brain Injury using Interactive Visuotactile Virtual Environment

by Alen Hajnal and Mohd Fairuz Shiratuddin

Innovations in Computing Sciences and Software Engineering, 2010

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A proposed framework for an Interactive Visuotactile 3D Virtual Environment system for visuomotor rehabilitation of stroke patients

by Alen Hajnal, Mohd Fairuz Shiratuddin, and Gabor Legradi

2012 International Conference on Computer & Information Science (ICCIS), 2012

Stroke is the second greatest killer and one of the leading causes of disability. One of the resu... more Stroke is the second greatest killer and one of the leading causes of disability. One of the results of stroke is the partial loss of vision with apparent blindness in certain parts of the visual field. Current vision restoration therapy and rehabilitation methods have not shown permanent treatment results for this type of partial loss of vision. Our research proposes the framework to design and develop a computer based vision restoration training and therapy system using Natural User Interfaces (NUIs) in an Interactive Visuotactile 3D Virtual Environment (IV-3DVE). This paper presents a proposed framework for the IV-3DVE system for visual restoration for stroke patients. This paper also provides a brief introduction to vision restoration treatment, the use of virtual environment technologies in sensorimotor rehabilitation, and natural user interfaces.

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Haptic selective attention by foot and by hand

by Claudia Carello and Alen Hajnal

Neuroscience Letters, 2007

Nonvisual perceptions of a wielded object's spatial properties are based on the quantities expres... more Nonvisual perceptions of a wielded object's spatial properties are based on the quantities expressing the object's mass distribution, quantities that are invariant during the wielding. The mechanoreceptors underlying the kind of haptic perception involved in wielding -referred to as effortful, kinesthetic, or dynamic touch -are those embedded in the muscles, tendons, and ligaments. The present experiment's focus was the selectivity of this muscle-based form of haptic perception. For an occluded rod grasped by the hand at some intermediate position along its length, participants can attend to and report selectively the rod's full length, its partial lengths (fore or aft of the hand), and the position of the grip. The present experiment evaluated whether participants could similarly attend selectively when wielding by foot. For a given rod attached to and wielded by foot or attached to (i.e. grasped) and wielded by hand, participants reported (by magnitude production) the rod's whole length or fractional length leftward of the point of attachment. On measures of mean perceived length, accuracy, and reliability, the degree of differentiation of partial from full extent achieved by means of the foot matched that achieved by means of the hand. Despite their neural, anatomical, and experiential differences, the lower and upper limbs seem to abide by the same principles of selective muscle-based perception and seem to express this perceptual function with equal facility.

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The Perception of Distance on a Slope

by Alen Hajnal and D. Bunch

Journal of Vision, 2012

Postural Sway is Affected by Visually Perceived Geographical Slant

by Alen Hajnal, John Shelley-Tremblay, and Deanna Rumble

Journal of Vision, 2013

Looking without seeing: Two puzzling findings

Journal of Vision, 2010

The perception of slope by eye, hand, foot, and finger: Evidence for an amodal vertical tendency

Journal of Vision, 2010

Perceiving action-relevant properties of tools through dynamic touch: Effects of mass distribution, exploration style, and intention

Journal of Experimental Psychology: Human Perception and Performance, 2011

At issue in the present series of experiments was the ability to prospectively perceive the actio... more 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.

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Lateral ball interception: hand movements during linear ball trajectories

by R. Arzamarski and Alen Hajnal

Experimental Brain Research, 2007

Part of understanding how acts are coordinated is identifying the information that guides movemen... more Part of understanding how acts are coordinated is identifying the information that guides movements. In the case of catching a ball within arm's reach, that identification has been complicated by empirical disparities concerning hand-movement reversals during catching. Jacobs and Michaels (J Exp Psychol Hum 32: 443-458, 2006) found unilateral reversals in a paradigm in which balls swung down in an arc; this implicated a particular optical variable, the ratio of lateral velocity to expansion velocity. Montagne et al. (Exp Brain Res 129:87-92, 1999) reported bilateral reversals when balls approached along a linear trajectory, which implicated a different variable, lateral ball position. The research reported here attempted to replicate Montagne et al.'s (Exp Brain Res 129:87-92, 1999) findings. In Experiment 1, participants caught balls rolling toward them across a table, under full lighting using monocular or binocular viewing; in Experiment 2, participants caught luminous balls with a luminous glove in an otherwise dark room. Using Montagne et al.'s (Exp Brain Res 129:87-92, 1999) criterion, we observed no movement reversals in any condition, though some aspects of hand movements suggested the relevance of lateral ball position. The results of Experiment 3, which asked perceivers to indicate only where rods pointed, suggested that lateral position effects were a bias that is unrelated to inter-ception. The ratio of lateral velocity to expansion appears to be a better variable for explaining hand trajectories in lateral interception.

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Location but not amount of stimulus occlusion influences the stability of visuo-motor coordination

by Alen Hajnal and Michael J. Richardson

Experimental Brain Research, 2009

The current study examined whether the amount and location of available movement information infl... more The current study examined whether the amount and location of available movement information influenced the stability of visuomotor coordination. Participants coordinated a handheld pendulum with an oscillating visual stimulus in an inphase and antiphase manner. The effects of occluding different amounts of phase at different phase locations were examined. Occluding the 0°/ 180°phase locations (end-points) significantly increased the variability of the visuomotor coordination. The amount of occlusion had little or no affect on the stability of the coordination. We concluded that the end-points of a visual rhythm are privileged and provide access to movement information that ensures stable coordination. The results are discussed with respect to the proposal of Bingham (Ecol Psychol 16:45-43, 2004) and Wilson et al. (Exp Brain Res 165:351-361, 2005) that the relevant information for rhythmic visual coordination is relative direction information.

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