Burkhart Fischer
and Klaus Hartnegg
Center
of Neuroscience
Optomotor Laboratory
University of Freiburg
email: bfischer@uni-freiburg.de
web: www.brain.uni-freiburg.de
Subitizing and Visual
Counting in Dyscalculia
Abstract:
The ability
of recognizing the number of briefly presented items without actually counting
is called subitizing (from lat. subito = suddenly). Adult subjects can subitize
3 to 4 items. For greater numbers the subjects begin a counting process, which
needs increasingly more time as the number of items increase. For children there
exits a long lasting development of accuracy and speed of subitizing and counting,
which lasts up to the adult age of 18 years.
This
study tests the hypothesis that children with difficulties in acquiring basic
arithmetic skills exhibit developmental deficits in subitizing and/or counting.
Altogether, 219 control and 156 subjects with dyscalculia in the age range
of 7 to 17 years were given a visual counting task, in which 1 to 9 items were
presented for 100 ms. The subjects had to press a digit key on a numerical keyboard
to indicate the number of items they had seen. Percentages of correct responses
and response times were recorded.
The
analysis shows systematic differences between control and dyscalculia children
increasing with age. The percentage of dyscalculia children performing below the
16-percentile of the age matched controls was estimated between 43% and 79% depending
on age.
Effects
of Daily Practice on Subitizing, Visual Counting, and Basic Arithmetic Skills
in Dyscalculia
Abstract
The ability
of subitizing and counting undergoes a long lasting development lasting up to
the age of 18 years. Large proportions of children with problems in acquiring
basic arithmetic skills exhibit developmental deficits in the correctness and
speed of this special visual capacity. The first study tests the possibility that
subitizing and counting can be improved by daily practice. Altogether, 152 subjects
(age 7 to 17 y) participated in the study. They were given a special task for
daily practice during a period of 21 days. The difficulty of the task was manipulated
by the maximum number of items (3 to 9) and the presentation time (300 too 100
msec).
The analysis
of the pre-post training data revealed that subitizing and counting were significantly
improved. About 75% of the subjects on average were able to improve both variables
determining the quality of task performance. The size of the training effects
and the percentage of successful subjects varied with age.
In
a second study it is shown that basic arithmetic operations were significantly
improved in a training as compared to a control group.
Prof.
Dr. Burkhart Fischer
is a neurobiophysicist at the Medical Faculty
of the University of Freiburg. His main research fields are: vision and eye movements
- development - deficits in dyslexica, ADHD, and in children with unclassified
developmental deficits. He has published more than 160 papers in international
journals. He discovered the optomotor reflex (Express Saccade) in 1983/84. He
also developed a new eye tracker "ExpressEye" for clinical application and tests
of dynamic vision "FixTest", and the low level auditory discrimination "FonoTest"
as well as the corresponding instruments for daily practice "FixTrain" and "FonoTrain".
His website is www.optom.de.
Klaus
Hartnegg
is a physicist and software specialist and member of the
Optomotor Brain Research Group of the Medical Faculty of the University of Freiburg.
He developed software for data acquisition and analysis used in this research
group and the software for controls of the test and training devices.