Fitts’ index of difficulty predicts the 1/f structure of movement amplitude time series

According to Fitts (1954), movement time (MT) is a function of the combined effects of movement amplitude and target width (index of difficulty). Aiming movements with the same index of difficulty and MT may have different planning and control processes depending on the specific combination of movement amplitude and target size. Trajectories were evaluated for a broad range of amplitudes and target sizes. A three-dimensional motion recording system (WATSMART) monitored the position of a stylus during aiming movements. MT results replicated Fitts’ Law. Analysis of the resultant velocity profiles indicated the following significant effects: As amplitude of movement increased, so did the time to peak resultant velocity; peak resultant velocity increased slightly with target size, and to a greater extent with increases in the amplitude of movement; the time after peak resultant velocity was a function of both amplitude and target size. Resultant velocity profiles were normalized in the time domain to look for scalar relation in the trajectory shape. This revealed that: the resultant velocity profiles were not symmetrical; the proportion of time spent prior to and after peak speed was sensitive to target size only, i.e. as target size decreased, the profiles became more skewed to the right, indicating a longer decelerative phase; for a given target size, a family of curves might be defined and scaled on movement amplitude. These results suggest that a generalized program (base trajectory representation) exists for a given target width and is parameterized or scaled according to the amplitude of movement.

Download Full-text

Vision Modulates the Structure of Movement-Amplitude Time Series

PsycEXTRA Dataset ◽

10.1037/e502412013-975 ◽

2012 ◽

Author(s):

Andrew B. Slifkin ◽

Jeffrey R. Eder

Keyword(s):

Time Series ◽

Movement Amplitude

Download Full-text

Head Rotation Movement Times

Human Factors The Journal of the Human Factors and Ergonomics Society ◽

10.1177/0018720817701000 ◽

2017 ◽

Vol 59 (6) ◽

pp. 986-994 ◽

Cited By ~ 1

Author(s):

Errol R. Hoffmann ◽

Alan H. S. Chan ◽

P. T. Heung

Keyword(s):

Transition Region ◽

Task Difficulty ◽

Head Rotation ◽

Movement Amplitude ◽

Display Area ◽

Input Mode ◽

Index Of Difficulty ◽

Head Rotations ◽

Ballistic Movements ◽

And Task

Objective: The aim of this study was to measure head rotation movement times in a Fitts’ paradigm and to investigate the transition region from ballistic movements to visually controlled movements as the task index of difficulty (ID) increases. Background: For head rotation, there are gaps in the knowledge of the effects of movement amplitude and task difficulty around the critical transition region from ballistic movements to visually controlled movements. Method: Under the conditions of 11 ID values (from 1.0 to 6.0) and five movement amplitudes (20° to 60°), participants performed a head rotation task, and movement times were measured. Results: Both the movement amplitude and task difficulty have effects on movement times at low IDs, but movement times are dependent only on ID at higher ID values. Movement times of participants are higher than for arm/hand movements, for both ballistic and visually controlled movements. The information-processing rate of head rotational movements, at high ID values, is about half that of arm movements. Conclusion: As an input mode, head rotations are not as efficient as the arm system either in ability to use rapid ballistic movements or in the rate at which information may be processed. Application: The data of this study add to those in the review of Hoffmann for the critical IDs of different body motions. The data also allow design for the best arrangement of display that is under the design constraints of limited display area and difficulty of head-controlled movements in a data-inputting task.

Download Full-text

The LDE-Type Flare Occurrence (1969-1993)

International Astronomical Union Colloquium ◽

10.1017/s0252921100025458 ◽

1994 ◽

Vol 144 ◽

pp. 279-282

Author(s):

A. Antalová

Keyword(s):

Time Series ◽

Fourier Analysis ◽

Sunspot Cycle ◽

List Type ◽

Type Number ◽

Solar Cycles ◽

Type Iv ◽

Long Duration ◽

Cycle Maximum ◽

Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

Download Full-text