| Visual and Auditory Attention from Heading in Soccer |
By Parmjit Sanghera and Mark Stone
Heading the ball is a common tactic and skill in soccer. This study examined the effects of heading the ball on four measures of attention and short-term memory by comparing amateur players with non-players. [This Abstract provides a coach’s summary with statistical details provided in the Technical Appendix.] Heading the ball raises the question of possible brain impairment as a consequence of concussion or closed head injury. Research has shown a high incidence for sustaining a concussion, particularly in male players (Barnes, Cooper, Kirkendall, McDermontt, Jordan & Garrett, 1998; Boden, Kirkendall & Garrett, 1998; Delaney, Lacroix, Leclerc & Johnston, 2002).
This study used The Knox Cube Test (KCT-R) and three subtests from the Wechsler Adult Intelligence Scale (WAIS-III) to discern score differences between amateur soccer players and a control group of non-soccer players. The KCT-R is a non-verbal test of visual attention and short-term memory. John Knox developed it for use in screening immigrants to Ellis Island at the turn of the 19th century. A revised version KCT-R (Stone 2002) increased the number of items and updated the norms. Digit Span Forward (DSF), Digit Span Backwards (DSB) and Letter Number Sequencing (LNS) were utilized from the WAIS-III, a well-know instrument for measuring mental functioning.
EXPERIMENTAL AND CONTROL SAMPLES
Thirty football/soccer players comprised the experimental group, and 50 subjects, all non-players, comprised the control group. The soccer players ranged in age from 18 to 40, with a mean age of 28 years. Education ranged from 12 to 18 years of completed schooling with an average of 14.33 years. Ethnicity as indicated by the players was 43.33 percent Asian, 40.0 percent Caucasian, 10 percent Jamaican, 3.33 percent African and 3.33 percent Arabic. Forty percent of the experimental sample indicated they were born in Canada. Of the individuals born abroad, the majority were born in India, followed by the United Kingdom. The average number of years lived in Canada was 15.67 years.
The control group of non-football/soccer players ranged in age from 18 to 50, with a mean age of 32.6 years. Years of completed schooling ranged from 12 to 23 years, with an average of 14.37 years. The ethnicity of the non-player group as described by the players was Asian 34 percent, Caucasian 54 percent, Jamaican 8 percent and 4 percent African. Fifty-four percent were born in Canada, and the remainder born abroad with an average residence in Canada of 17.34 years.
Exclusion criteria also were applied to remove test participants that were not deemed appropriate for this study. These criteria included a positive history of a head injury that was not soccer-related or other factors indicated by research to affect performance on cognitive measures of memory functioning. This included a diagnosis of a neurological and psychiatric condition, learning disabilities or a history of drug or alcohol abuse.
CONCUSSION EFFECTS
The soccer players were surveyed regarding position(s) played, number of years playing league soccer, average number of games played each year, average number of headers in a game and number of concussions sustained as a result of playing soccer. Those who said they has sustained a concussion were further questioned about when the concussion occurred, what symptom(s) were experienced, the length of time the symptom(s) were experienced, if they exited the game because of the injury, any medical attention received, if they obtained a diagnosis of concussion by a physician and when they returned to the game.
RESULTS
Results showed no significant differences on performance scores for the KCT-R, Digit Span Forward, Digit Span Backward and the Letter Number Sequencing Test between the soccer players and the control group. The results remained non-significant when the effects of age and education were controlled. Results also showed no significant differences between players reporting concussions and non-concussions on these four measures. There also was no significant relationship between heading the ball and these scores on attention and short-term memory.
Qualitative analysis of responses indicated that seven soccer players reported sustaining a concussion in a game during the current year; one player reported sustaining a concussion one year ago, one player three years ago, one player eight years ago and one player 16 years past. One player reported three concussions occurring eight, 10 and 12 years ago, and one player reported a concussion, but could not remember when he sustained it. There was no pattern to the past headings and test performance.
Two players reported that they continued to play following the concussion, one player returned two days after sustaining a concussion, three players returned to play a week later and one player returned two weeks following his concussion. Six players reported dizziness as a consequence of heading the ball and two players reported “confusion.” One player reported “whiplash” injury and neck pain. None of the players sought medical attention.
DISCUSSION
Results of this study found no statistically significant differences on performance scores for KCT-R, Digit Span Forward, Digit Span Backward and the Letter Number Sequencing Test between the soccer players and the control group. The results remained non-significant when the effects of age and education were controlled. Results showed no significant differences between players reporting concussions and non-concussions on the four measures. Additionally, there was no significant relationship between heading the ball and these performance scores. However, these tests may not be sensitive to subtle injury, and long-term followup has not been completed.
Qualitative analysis on data collected about concussions did raise some concerns. Of the seven amateur soccer players who reported sustaining a concussion during soccer play, two continued playing the game, four returned to play within a week of the injury and one returned after two weeks. None of the players sought medical attention, placing them at risk for Second Impact Syndrome (SIS), the implications of which could be dire (Kelly & Rosenberg, 1997). Soccer players should be educated on the symptoms and effects of concussion to aid diagnosis and treatment, should they incur an injury.
Larger sample sizes are needed for future investigation of these variables, allowing stratification by age and education with sufficient numbers in each grouping category. The number of participants in selected age groups in the first sample differed, and this matter would be eliminated with sufficient numbers in each category. A larger sample size would allow for within-group comparisons for the soccer players (i.e. comparing those players who had sustained one concussion with those who had sustained successively more concussions and to the control group). Age is a critical issue. Adults typically have achieved full brain development, while children and adolescents are still maturing. The issue of brain impairment in adults is very different from trauma to still-developing brain functions. This study did not evaluate all of the important facets of brain functioning, which would necessitate a complex and expensive assessment, so not all areas of brain functioning were evaluated.
Players also vary greatly in how they head the ball physically and in emotional intensity in a game. It is hard to control for these variables, which may influence results. Allowing the ball to make contact vs. initiating a directive force can produce differences. The physics involved in heading have not been fully investigated to help explain what produces injury.
Technical Appendix
HYPOTHESIS
A statistically significant difference between soccer players and non-players was hypothesized, given the research.
INSTRUMENTS
The Knox Cube Test-Revised (KCTR) is a non-verbal performance test used to measure attention and short-term memory (Stone, 2002). The original version was developed by John Knox, M.D., in 1914. It was one test in his battery for screening immigrants at Ellis Island prior to entering the United States of America. Knox’s original test cubes can be seen in the museum at Ellis Island. He developed several block-tapping series, presented in order of difficulty, allowing him to obtain a simple measure of mental alertness. The KCT tapping series is useful because it can be presented to people representing many different languages and cultures (Stone, 2002, p. 27).
Knox’s Cube Test has been revised several times for inclusion in test batteries by Pinter (1923), Yerkes (1921), Drever & Collins (1928), Amoss (1936), Goodnough (1940), Arthur (1943, 1947), Babcock (1965) and Stone (1981/1983). The test consists of four black cubes fastened to a board (12 inches x 2 inches) two inches apart. The examinee imitates a tapping series performed by the examiner. Knox used only a few tapping series. The KCT-R uses 26 tapping series arranged by increasing tapping length, producing item difficulty. It is introduced with two practice trials. The KCT-R provides norms on 3,173 persons, ages 3 to 84 from four Midwestern states: Iowa, Illinois, Indiana and Wisconsin. There were 1,571 males and 1,602 females in the norm group. The racial composition was 66 percent Caucasian, 29 percent African-American, 4 percent Hispanic and 1 percent Asian.
The KCT-R items are administered in their order of difficulty and concluded after five consecutive failures. This makes diagnosis of response patterns possible (Stone, 2002, pp. 27-29). A surprise success (S) or failure (F) is an occasion in which the examinee achieves higher or lower that expected for the run of correct or incorrect responses. The sequence 111111110000100000 = 9 illustrates a Surprise Success following four consecutive failures, and 101111111100000 = 9 illustrates a Surprise Failure followed by eight consecutive successes. A surprise signals an unexpected outcome in a sequence of responses. The infrequency of surprises indicates very little irregularity in the sequence of responses for these persons.
The WAIS-III (1997) is a well-known and commonly used measure of intelligence. Several subtests tap measures of attention and short-term memory; Digit Span Forward (DSF), Digit Span Backward (DSB) and the Letter Number Sequencing Test (LNST). DSF requires the subject to repeat verbatim an orally presented progressively increasing sequence of numbers. DSB is similar except that the subject must repeat the sequence in reverse order (backwards). LNST utilizes an orally presented and varied sequence of letters and numbers the subject tracks and orally repeats with the numbers in ascending order and the letters in alphabetical order. All three subtests have reasonably high reliability ranging, from .79 to .86. Norms are derived from 2,450 adults following the demographic guidelines of the U.S. Bureau of the Census.
STATISTICAL RESULTS
The KCT-R was used together with three other measures taken from the WAIS-III (1997): Digit Span Forward (DSF), Digit Span Backwards (DSB) and Letter Number Sequencing (LNS). Table 1 gives the experimental and control group means and standard deviations for each test.
No statistically significant differences were found between the experimental and control groups for any of the four measures:
KCT-R (t = 1.71, df = 78, p = 0.09); DSF (t = 1.38, df = 78, p = 0.17); DSB (t = 1.44, df = 78, p = 0.15); LNS – t = 1.10, df = 78, p = 0.27.
When age and level of education for the participants in both groups were controlled using ANCOVA, the results again were not statistically significant.
The KCT-R was found useful when administered to these samples not previous included in any normative studies. It appears easily administered across cultures. Lower scores for the Indian sample appear associated to age and education. The KCT-R was found no less useful than the three subtests of the WAIS-III used to evaluate soccer players for the effects of heading the ball.
Logistic regression was conducted to investigate if these four measures could predict membership in either the soccer-playing sample or the control group. This analysis was not statistically significant for all four measures, but KCT-R produced the highest coefficient of the four predictor variables.
Test performance was investigated for 21 players who provided information about heading the ball. There was no significant correlation between KCT-R, (r = 0.26); DSF, (r = - 0.15); DSB, (r = 0.22); and LNS, (r = 0.22) and the number of headers in a game.
All these correlation values are within chance levels of a null hypothesis of r = 0.0.
Notes
1. See Best Test Design (Wright & Stone, 1979) pp. 191-204.
2. See Best Test Design (Wright & Stone, 1979) pp. 171-174.
3. See Best Test Design (Wright & Stone, 1979) pp. 174-176.
References
Amoss, H. (1936). Ontario school ability examination. Toronto: Ryerson Press.
Arthur, G. (1943). A point-scale of performance. Itasca: Stoelting.
Babcock, H. (1965). Babcock test of mental deficiency. Itasca: Stoelting.
Barnes, B.C., Cooper, L., Kirkendall, D.T., McDermott, T.P., Jordan, B.D., & Garrett, Jr.,
W.E. (1998). Concussion history in elite male and female soccer players. The American Journal of Sports Medicine, 26(3), 433-438.
Boden, B.P., Kirkendall, D.T., & Garrett, Jr., W.E. (1998). Concussion incidence in elite college soccer players. The American Journal of Sports Medicine, 26(2), 238-241.
Delaney, J.S., Lacroix, V.J., Leclerc, S., & Johnston, K.M. (2002). Concussions among university football and soccer players. Clinical Journal of Sport Medicine, 12, 331-338.
Drever, J. & Collins, M. (1928). Performance tests of intelligence. Edinburgh:
Oliver and Boyd.
Goodnough, F. (1940). Minnesota preschool scale. Circle Pines, MN: American Guidance Service.
Kelly, J. P., & Rosenberg, J. H. (1997). Diagnosis and management of concussion in sports. Neurology, 48, 575-580.
Pinter, R. & Patterson, D. (1923). A scale of performance tests. New York: Appleton.
Stone, M. & Wright, B. (1981/1983). Measuring attending behavior and short-term memory with Knox’s Cube Test. Educational and Psychological Measurement 43 (3), 803-814.
Stone M. (2002). Knox’s Cube Test Revised a Manual for Clinical and Experimental Uses. Wood Dale, Illinois: Stoelting Co.
Yerkes, R. (1921). Psychological examining in the U.S. Army. Memoirs of National Academy of Sciences, 15.
Editor's Note: This article originally appeared in the March-April 2009 issue of Soccer Journal.
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