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Is Fitts’ Law Continuous in Discrete Aiming?  [PDF]
Rita Sleimen-Malkoun, Jean-Jacques Temprado, Raoul Huys, Viktor Jirsa, Eric Berton
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041190
Abstract: The lawful continuous linear relation between movement time and task difficulty (i.e., index of difficulty; ID) in a goal-directed rapid aiming task (Fitts’ law) has been recently challenged in reciprocal performance. Specifically, a discontinuity was observed at critical ID and was attributed to a transition between two distinct dynamic regimes that occurs with increasing difficulty. In the present paper, we show that such a discontinuity is also present in discrete aiming when ID is manipulated via target width (experiment 1) but not via target distance (experiment 2). Fitts’ law’s discontinuity appears, therefore, to be a suitable indicator of the underlying functional adaptations of the neuro-muscular-skeletal system to task properties/requirements, independently of reciprocal or discrete nature of the task. These findings open new perspectives to the study of dynamic regimes involved in discrete aiming and sensori-motor mechanisms underlying the speed-accuracy trade-off.
Performance is not Related to Perception of Target Width in Fitts’ Law  [cached]
Zelaznik Howard N.,Croxall Roxanne,Vanhooser Jake
BIO Web of Conferences , 2011, DOI: 10.1051/bioconf/20110100100
Abstract: We report a new experiment in a series of studies in which research participants perform a Fitts’ Law repetitive task, and then are required to judge the width of the target that was utilized. The first two experiments previously reported showed no relation between perception and performance. However in those two experiments subjects were never provided with feedback on their performance. In the current study, we provided participants with their performance score. Providing their performance score did not produce a relation between target width perception and performance. We posit that sports studies that have shown this relation are the results of intimate knowledge of what it means to perform well. Our inexperienced Fitts’ Law participants lacked such an understanding.
On the Measurement of Movement Difficulty in the Standard Approach to Fitts' Law  [PDF]
Yves Guiard, Halla B. Olafsdottir
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024389
Abstract: Fitts' law is an empirical rule of thumb which predicts the time it takes people, under time pressure, to reach with some pointer a target of width W located at a distance D. It has been traditionally assumed that the predictor of movement time must be some mathematical transform of the quotient of D/W, called the index of difficulty (ID) of the movement task. We ask about the scale of measurement involved in this independent variable. We show that because there is no such thing as a zero-difficulty movement, the IDs of the literature run on non-ratio scales of measurement. One notable consequence is that, contrary to a widespread belief, the value of the y-intercept of Fitts' law is uninterpretable. To improve the traditional Fitts paradigm, we suggest grounding difficulty on relative target tolerance W/D, which has a physical zero, unlike relative target distance D/W. If no one can explain what is meant by a zero-difficulty movement task, everyone can understand what is meant by a target layout whose relative tolerance W/D is zero, and hence whose relative intolerance 1–W/D is 1 or 100%. We use the data of Fitts' famous tapping experiment to illustrate these points. Beyond the scale of measurement issue, there is reason to doubt that task difficulty is the right object to try to measure in basic research on Fitts' law, target layout manipulations having never provided users of the traditional Fitts paradigm with satisfactory control over the variations of the speed and accuracy of movements. We advocate the trade-off paradigm, a recently proposed alternative, which is immune to this criticism.
Usage analysis for applying Fitts'' law in context of mobile/wearable computing
Fitts’ 模型在移动与可穿戴计算交互中的可用性研究*

SONG Hai-tao,LIU Huan-yu,
宋海涛
,刘桓宇

计算机应用研究 , 2011,
Abstract: Mobile and wearable computing have becoming bloom in these years.For which the interaction usually based on the restricted field of view devices,e.g.hand-held small display and head mounted display,as well as the multi-touch pointing device.However,the encountered various display field of view and small targets while interacting with those devices may significantly affect the interaction efficiency,and further influence the usability of traditional Fitts' law,the common tool to study it.This paper conducted...
Measurement of the Robot Motor Capability of a Robot Motor System: A Fitts’s-Law-Inspired Approach  [PDF]
Hsien-I Lin,C. S. George Lee
Sensors , 2013, DOI: 10.3390/s130708412
Abstract: Robot motor capability is a crucial factor for a robot, because it affects how accurately and rapidly a robot can perform a motion to accomplish a task constrained by spatial and temporal conditions. In this paper, we propose and derive a pseudo-index of motor performance ( pI p) to characterize robot motor capability with robot kinematics, dynamics and control taken into consideration. The proposed pI p provides a quantitative measure for a robot with revolute joints, which is inspired from an index of performance in Fitts’s law of human skills. Computer simulations and experiments on a PUMA 560 industrial robot were conducted to validate the proposed pI p for performing a motion accurately and rapidly.
A Note on the Validity of the Shannon Formulation for Fitts’ Index of Difficulty  [PDF]
Ian Scott MacKenzie
Open Journal of Applied Sciences (OJAppS) , 2013, DOI: 10.4236/ojapps.2013.36046
Abstract:

The three most common variations of Fitts’ index of difficulty are the Fitts formulation, the Welford formulation, and the Shannon formulation. A recent paper by Hoffmann [1] critiqued the three and concluded that the Fitts and Welford formulations are valid and that the Shannon formulation is invalid. In this paper, we challenge Hoffmann’s position regarding the Shannon formulation. It is argued that the issue of validity vs. invalidity is ill-conceived, given that Fitts’ law is a “model by analogy” with no basis in human motor control. The relevant questions are of utility: Does a model work? How well? Is it useful? Where alternative formulations exist, they may be critiqued and compared for strengths and weaknesses, but validity is an irrelevant construct. In a reanalysis of data from Fitts’ law experiments, models built using the Shannon formulation are (re)affirmed to be as good as, and generally better than, those built using the Fitts or Welford formulation.

Auditory Cortical Detection and Discrimination Correlates with Communicative Significance  [PDF]
Robert C. Liu,Christoph E. Schreiner
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0050173
Abstract: Plasticity studies suggest that behavioral relevance can change the cortical processing of trained or conditioned sensory stimuli. However, whether this occurs in the context of natural communication, where stimulus significance is acquired through social interaction, has not been well investigated, perhaps because neural responses to species-specific vocalizations can be difficult to interpret within a systematic framework. The ultrasonic communication system between isolated mouse pups and adult females that either do or do not recognize the calls' significance provides an opportunity to explore this issue. We applied an information-based analysis to multi- and single unit data collected from anesthetized mothers and pup-na?ve females to quantify how the communicative significance of pup calls affects their encoding in the auditory cortex. The timing and magnitude of information that cortical responses convey (at a 2-ms resolution) for pup call detection and discrimination was significantly improved in mothers compared to na?ve females, most likely because of changes in call frequency encoding. This was not the case for a non-natural sound ensemble outside the mouse vocalization repertoire. The results demonstrate that a sensory cortical change in the timing code for communication sounds is correlated with the vocalizations' behavioral relevance, potentially enhancing functional processing by improving its signal to noise ratio.
Auditory Cortical Detection and Discrimination Correlates with Communicative Significance  [PDF]
Robert C Liu ,Christoph E Schreiner
PLOS Biology , 2007, DOI: 10.1371/journal.pbio.0050173
Abstract: Plasticity studies suggest that behavioral relevance can change the cortical processing of trained or conditioned sensory stimuli. However, whether this occurs in the context of natural communication, where stimulus significance is acquired through social interaction, has not been well investigated, perhaps because neural responses to species-specific vocalizations can be difficult to interpret within a systematic framework. The ultrasonic communication system between isolated mouse pups and adult females that either do or do not recognize the calls' significance provides an opportunity to explore this issue. We applied an information-based analysis to multi- and single unit data collected from anesthetized mothers and pup-na?ve females to quantify how the communicative significance of pup calls affects their encoding in the auditory cortex. The timing and magnitude of information that cortical responses convey (at a 2-ms resolution) for pup call detection and discrimination was significantly improved in mothers compared to na?ve females, most likely because of changes in call frequency encoding. This was not the case for a non-natural sound ensemble outside the mouse vocalization repertoire. The results demonstrate that a sensory cortical change in the timing code for communication sounds is correlated with the vocalizations' behavioral relevance, potentially enhancing functional processing by improving its signal to noise ratio.
On the scaling law for cortical magnification factor  [PDF]
Alexei A. Koulakov
Quantitative Biology , 2010,
Abstract: Primate visual system samples different parts of the world unevenly. The part of the visual scene corresponding to the eye center is represented densely, while away from the center the sampling becomes progressively sparser. Such distribution allows a more effective use of the limited transfer rate of the optic nerve, since animals can aim area centralis (AC) at the relevant position in the scene by performing saccadic eye movements. To locate a new saccade target the animal has to sample the corresponding region of the visual scene, away from AC. In this work we derive the sampling density away from AC, which optimizes the trajectory of saccadic eye movements. We obtain the scaling law for the sampling density as a function of eccentricity, which results from the evolutionary pressure to locate the target in the shortest time under the constraint of limited transfer rate of the optic nerve. In case of very small AC the visual scene is optimally represented by logarithmic conformal mapping, in which geometrically similar circular bands around AC are equally represented by the visual system. We also obtain corrections to the logarithmic scaling for the case of a larger AC and compare them to experimental findings.
Dementia in Parkinson's Disease Correlates with α-Synuclein Pathology but Not with Cortical Astrogliosis  [PDF]
Simone A. van den Berge,Josta T. Kevenaar,Jacqueline A. Sluijs,Elly M. Hol
Parkinson's Disease , 2012, DOI: 10.1155/2012/420957
Abstract: Dementia is a common feature in Parkinson’s disease (PD) and is considered to be the result of limbic and cortical Lewy bodies and/or Alzheimer changes. Astrogliosis may also affect the development of dementia, since it correlates well with declining cognition in Alzheimer patients. Thus, we determined whether cortical astrogliosis occurs in PD, whether it is related to dementia, and whether this is reflected by the presence of glial fibrillary acidic protein (GFAP) and vimentin in cerebrospinal fluid (CSF). We have examined these proteins by immunohistochemistry in the frontal cortex and by Western blot in CSF of cases with PD, PD with dementia (PDD), dementia with Lewy bodies (DLB) and nondemented controls. We were neither able to detect an increase in cortical astrogliosis in PD, PDD, or DLB nor could we observe a correlation between the extent of astrogliosis and the degree of dementia. The levels of GFAP and vimentin in CSF did not correlate to the extent of astrogliosis or dementia. We did confirm the previously identified positive correlation between the presence of cortical Lewy bodies and dementia in PD. In conclusion, we have shown that cortical astrogliosis is not associated with the cognitive decline in Lewy body-related dementia. 1. Introduction Parkinson’s disease (PD) is a progressive neurological disorder characterized by motor symptoms such as tremor, bradykinesia, rigidity, and postural instability. It is associated with an almost complete degenerative loss of dopamine neurons in the substantia nigra (SN) pars compacta and the presence of Lewy bodies (LBs) and Lewy neurites (LNs). The latter pathological hallmarks initially occur, according to Braak and colleagues, in the glossopharyngeal and vagal nerves and the anterior olfactory nucleus, and thereafter spread to other brain nuclei and cortical areas [1]. This topological progression of the disease, however, is currently being critically evaluated in the field [2–4]. In any case, a major component of these LBs and LNs is an aggregated form of the presynaptic protein α-synuclein [1]. More recently, it has become apparent that cognitive dysfunction is also an important clinical component of PD. About two-third of the patients develop cognitive deficits within 3.5 years from the disease onset [5], and up to 40% of idiopathic PD patients will develop dementia (PD with dementia, PDD) based on population-based studies (reviewed in [6]). The cognitive deficits and dementia are considered to be the result of the limbic and cortical LBs [5], although the presence of Alzheimer changes, such as
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