ABSTRACT
The second to fourth digit ratio (2D:4D), is a sexually diamophic trait, with males on the average having lower ratios than females. 2D:4D is established in the uterus, therefore its found in fetus, children, and unaffected by puberty. It also appear to be universal across ethnic groups, and it exist in mammals and other primates. 2D:4D is positively associated with prenatal estrogen and negatively associated with prenatal testosterone. The present study is primarily aimed at investigating the existence of the association between digit ratio (2D:4D), with academic performance of secondary school students in Kaduna, Nigeria. A total of 462 students (239 males and 223 females) participated in the study from three secondary schools in Kaduna metropolis. Relevant data were collected through a self-administered questionares after which certain anthropometric measurements including digit length, weight, height and some circumferences which include head, neck, hip and waist. Academic performance of the students were measured from the terminal examinations results obtained from the schools managements. Our study found that low 2D:4D (a correlate of high prenatal testosterone and low prenatal oestrogen) is associated with better performance on Mathematics in males but not in females. There were no correlation between 2D:4D and academic performance, based on the three other subjects considered among the secondary school students in Kaduna, Nigeria. The study also agree with the literature that says 2D:4D ratio tend to be more on the right hand than the left hand. We therefore conclude that 2D:4D ratio is associated with better performance in Mathematics and numerical capability in boys
TABLE OF CONTENTS
Title Page ———————————————————————————————- i
Declaration ——————————————————————————————– ii
Approval page —————————————————————————————- iii
Acknowledgements ———————————————————————————- iv
Dedication ——————————————————————————————— vi
Table of Contents ———————————————————————————– vii
List of Tables —————————————————————————————– xi
List of Figures ————————————————————————————— xiv
List of Appendices ———————————————————————————- xv
Abstract ———————————————————————————————– xvi
1. INTRODUCTION ————————————————————————— 1
1.1 Background of Study ———————————————————————— 1
1.2 Statement of Research Problem ———————————————————— 5
1.3 Justification ———————————————————————————– 5
1.4 Aims and Objectives of Study————————————————————– 6
1.4.1 Aims of Study—————————————————————————- 6
1.4.2 Objectives of Study ——————————————————————— 6
1.5 Significance of Study ———————————————————————– 7
1.6 Study Hypotheses —————————————————————————-7
1.7 Encountered limitations of the Study —————————————————– 8
2. LITERATURE REVIEW——————————————————————- 9
2.1 Evidence of Androgen Effect on Digit Ratio ——————————————– 9
2.2 Association of Digit Ratio and Some Diseases Condition —————————-13
2.3 Geographic and Ethnic Variation in Digit Ratio—————————————-16
2.4 Digit Ratio and Birth Weight————————————————————–17
2.5 Digit Ratio and Sporting Ability———————————————————-18
2.6 Digit Ratio and Fertility——————————————————————- 21
2.7 Digit Ratio and Academic Performance————————————————- 24
2.8 Head size and Academic Performance ———————————————— -29
2.9 Digit Ratio Research in Non-Human Animals —————————————– 32
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3. MATERIALS AND METHODS ———————————————————- 33
3.1 Research Participants————————————————————————- 33
3.2 Study Location ——————————————————————————– 33
3.3 Kaduna State———————————————————————————– 33
3.3.1 Drainage———————————————————————————– 35
3.3.2 The climate of Kaduna——————————————————————- 35
3.3.3 Natural vegetation ———————————————————————– 36
3.4 Methodology ———————————————————————————– 37
3.5 Data Collection Technique ——————————————————————- 37
3.6 Sampling Size Determinaton —————————————————————- 37
3.7 Anthropometry ——————————————————————————— 38
3.7.1 Finger Length Measurements —————————————————————- 38
3.7.2 Height ——————————————————————————————–38
3.7.3 Weight——————————————————————————————– 39
3.7.4 Head Circumference—————————————————————————- 39
3.7.5 Waist Circumference (WC)——————————————————————- 40
3.7.6 Hip Circumference (HC) ———————————————————————- 40
3.7.7 Neck Circumference (NC) ——————————————————————– 40
3.8 Anthropometric Correlations ——————————————————————— 41
3.8.1 2D:4D Ratio and Sex ————————————————————————– 41
3.8.2 2D:4D Ratio and Waist-Hip Ratio (WHR) ————————————————- 41
3.8.3 2D:4D Ratio and Ethnicity ——————————————————————- 41
3.8.4 2D:4D Ratio and Heterosis ——————————————————————- 41
3.8.5 2D:4D Ratio and Body Mass Index (BMI) ————————————————- 42
3.8.6 2D:4D Ratio and head circumference —————————————————— 42
3.8.7 Head Circumference and Academic Performance ———————- —————- 42
3.9 Ethical Approval ———————————————————————————- 42
3.10 Inclusion And Exclusion Criteria ————————————————————- 42
3.10.2 Inclusion Criteria ——————————————————————————– 43
3.10.3 Exclusion Criteria——————————————————————————– 43
3.11 Statistical Analysis ——————————————————————————- 43
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4. RESULTS —————————————————————————————– -45
4.1 Analysis of Study Population ——————————————————————- -45
4.2 Anthropometric Variables of Overall Sample ———————————————— -46
4.3 Anthropometric Variables according to Future Ambition———————————– 55
4.4 Anthropometric Variables according to Social Status ————————————— 59
4.5 Anthropometric Variables according to School Attendance Type ————————– 68
4.6 Correlation Matrix Tables Results ————————————————————– 73
5. DISCUSSION ————————————————————————————–78
6. Summary, Conclusion and Recommendations ————————————————-85
6.1 Conclusion ——————————————————————————————88
6.2 Recommendations ——————————————————————————— 89
6.3 Contribution to knowledge ———————————————————————– 90
References ——————————————————————————————– 91
CHAPTER ONE
INTRODUCTION
1.1 Background of Study
The second to forth finger length ratio (2D:4D) is a sexually dimorphic trait that has been known for over 100 years (Baker, 1888), with men, on average, having lower 2D:4Ds than women do. Unlike sexually dimorphic characteristics that appear at puberty, 2D:4D is established by the 13th week after conception (Garn et al., 1975). ), therefore this dimorphism found in the fetus (Malas et al., 2005) and in children (Manning et al., 1998; McIntyre et al., 2005); is unaffected by puberty (Trivers et al., 2006) and appeared to be universal across ethnic groups (Manning, 2002) and has been shown to exist in mammals and other primates (Burley and Foster 2004; Brown et al., 2002). Based on a large number of studies, it has been concluded that 2D:4D is positively associated with prenatal estrogen and negatively associated with prenatal testosterone (Manning, 2002; Danborno et al., 2007 and Breedlove 2010). Evidence such as this does not include direct measurements of prenatal testosterone, but its sex dependent pattern led Manning et al., (1998) to suggest that 2D:4D may be negatively correlated to prenatal testosterone and positively related to prenatal estrogen.
In recent years, the so-called second (2D) to fourth (4D) digit ratio has received a lot of research attention. In the past 7 years, many papers have documented relationship between 2D:4D and human traits and behaviors. This ratio seems to be established in utero (Csatho et al. 2003a; Manning et al., 1998; Williams et al., 2003). Some evidence suggests that the index finger (digit 2) is an indicator of prenatal estrogen levels while the length of the ring finger (digit 4) appears to
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be determined by prenatal testosterone levels (Manning, 2002). Although both digits could be investigated in isolation as they would indicate different hormones, research typically looks at the correlates of the ratio between 2nd and 4th digit (2D:4D). There are some exceptions to this general practice. For instance, Robinson and Manning (2000) found an association between homosexuality and the 4th, but not the 2nd digit (controlled for height); Manning and Wood (in Manning, 2002) report that boys with long 4th digits adjusted for height reported more physical aggression compared to participants with short 4th digits while recently Danborno et al., (2010) were able to show that the ratio can be a predictor of birth weight.
However, the 2D:4D literature suggests that the balance between male and female prenatal hormone levels rather than these hormone levels in isolation triggers neurological and behavioral processes (Manning, 2002). The growing list of psychological correlates of 2D:4D and the short list of psychological correlates with the digits separately may suggest that investigating the main effects of one sexual hormone might not make too much sense without taking into account the other hormone level. Note that this remark applies to the role of hormone levels in utero and does not necessarily generalize to fluctuating hormone levels.
The heritability of 2D:4D has been examined in three twin samples ( Paul et al., 2006; Voracek and Dressler 2007, and Gobrogge et al., 2008). The point estimates from these studies indicate substantial additive genetic effects. However, it is also obvious, from the wide confidence intervals, that the power of previous studies to detect significant common environmental effects, or sex differences in the variance components, was limited. Within each sex, 2D:4D has been
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found to be associated with a variety of physical and psychological characteristics. For example, men with lower 2D:4D are more aggressive, more athletic, less feminine (on the Bem Sex Role Inventory), and more musically talented (Bailey and Hurd, 2005; Manning and Taylor, 2001; Rammsayer and Troche, 2007; Sluming and Manning, 2000). Women with lower 2D:4D have higher waist-to-hip ratio, are more masculine (on the Bem Sex Role Inventory), and are more athletic (Csathó et al., 2003a; Manning et al., 2000; Pokrywka et al., 2005). Among both men and women, 2D:4D is correlated positively with verbal intelligence and agreeableness, and negatively with numerical intelligence and physical fitness (Hönekopp et al., 2006; Luxen and Buunk, 2005). Autistic individuals have also been found to be gifted in identifying recurrent patterns, processing perceptual information, and often have exceptional memories and are less likely to misremember data (Mottron, 2011). These are characteristics that are useful in order to perform well in practical and theoretical examinations.
A number of recent studies have reported an association between digit ratio and performance on a range of measures assessing cognitive abilities and personality (e.g., Austin et al., 2002; Bailey and Hurd, 2005; Csatho et al., 2003a; Manning, 2002), and sexual orientation and identity (e.g., Rahman and Wilson, 2003; Robinson and Manning, 2000; Williams et al., 2000). For example, a significant association between digit ratio and spatial navigation and picture recall skills has only been found for females (Csatho et al., 2003b) whilst significant associations with mental rotation ability and academic performance have typically only been reported for males (Manning and Taylor, 2001; McFadden and Romano et al., 2006), although Kempel et al., (2005) have recently reported poorer performance of high digit ratio females on mirror picture and shape unrolling tasks. Reports of digit ratio in relation to aspects of mathematical performance are less common.
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Luxen and Buunk (2005) found a significant correlation between right hand digit ratio and numerical skills, with numerical skills being higher in individuals with lower masculinised digit ratios. Kempel et al., (2005) also found that females with more masculinised digit ratios performed better on a numerical IQ task (continuing numerical series). In the mathematical cognition literature, it has been argued that mathematical thinking depends in part on an underlying “number sense” (Dehaene et al., 2003), which is biologically determined and has a long evolutionary history. This number sense allows us to compare and approximate numerical quantities, and such abilities have been repeatedly demonstrated in studies with very young infants (Lipton and Spelke, 2003; Xu, 2003).
Finally Hopp et al., (2012) have found that low 2D:4D is related to practical and theory examination marks in Brazilian male dental students. They suggest that their finding supports a theoretical link between high prenatal testosterone and high intelligence. The lack of a relationship between 2D:4D and examination marks in female dental students indicate that prenatal testosterone does not influence female intelligence in the same manner as that in males, even though the studies is consistent with that of Coco et al., (2011) evaluated a group of 48 male students, and found a significant correlation between 2D:4D and success in admission tests for a medical school in Italy
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1.2 Statement of Research Problem
In developing countries like Nigeria, anthropological data are scarce and where they are available, they are not properly documented. This make it difficult to evaluate some phenotypic, physiological and psychological characteristics from the available data. Recently, studies from 2D:4D ratio signals such qualities as height, intelligence, aggression, health and fertility in man, this study is intended to accumulate data on 2D:2D ratio among secondary schools students in Kaduna, Nigeria, and correlate it with some specific anthropometric parameters like head circumfernce, BMI, WHR etc.
1.3 Justification of the Study
Prenatal testosterone has been proposed to directly influence intelligence or academic performance by modulating the developmental processes of neuronal proliferation, migration, differentiation, and apoptosis. This is thought to increase the density of neuronal networks in certain areas of the brain related to cognition, learning and memory, either by decreasing apoptosis of brain cells during development, or increasing migration of cells to one of those areas (Mrazik & Dombrowski, 2010). Differences in prenatal hormone exposure can lead to different traits in personality, aggression, behaviour and ability to perform tasks such as playing sports, driving carefully, investing money or doing manual labour. Low 2D:4D has been correlated to success and profitability in financial trading (Coates et al., 2009), success in sports such as rugby, sprinting and running (Manning et al., 2007) and numeric capabilities and ability to understand information communication technology (Brosnan, 2006).
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In this present research, we consider the possibility that digit ratio (2D:4D), as a putative marker for prenatal testosterone (Manning 1998), could be use to provide a basis locally in which brilliant students can be selected based on the study of their digit ratio and to some extend, their head size. Recently, Hopp et al,. (2012 ) reported an association between 2D:4D and intelligence in dental students of a Brazillian University. In addition there is no published data about the relationship between digit ratio and academic performance in Nigerian children. It‟s against this backdrop that the present study seeks to find out what‟s the academic performance of students in relation to their 2D:4D in Nigeria with a view to finding out how it is influenced by other anthropometric parameters, ethnicity, and socio-economic factors and to make recommendations where necessary.
1.6 Aims of Study
This study is aim to investigate the exitence of association between 2D:4D ratio with academic performance of secondary school students in Kaduna, Nigeria.
1.7 Objectives of the Study
With the emergence of the importance of digit ratio as a pointer to height, intelligence, aggression, health and fertility, the present study is designed to investigate:
i. The relationship between 2D:4D and academic performance among secondary schools students.
ii. Sex differences in 2D:4D ratio among some Nigerians students.
iii. The relationship between 2D:4D and head circumference
iv. The relationship of 2D:4D ratio with BMI of students
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v. Relationship between 2D:4D and waist, hip and neck circumference.
1.4 Significance of Study
The results of the present study will provide bases in which brilliant students can easily be selected based on their head sizes and 2D:4D ratios. It could also be possible to use the data to determine in which course of study a student could performe well. The outcome of the study could also provide the basis for appealing to government at all levels to bring programs specifically to suit each of the people‟s peculiar needs. This study could help create awareness on the use of some body parameters to come to some psychological conclusions. This study will also create awareness to authorities and the general public on the importance of digit ratio as a pointer to certain biological attributes of man and demonstrate how the knowledge of biological anthropology applies to numerous fields of science and medicine
1.5 Hypothesis
a. There is a correlation between academic performance and digit ratio of the students
b. There is a negative relationship between 2D:4D with socio-economic status of the students.
c. There is a positive relationship between 2D:4D with height, weight, head circumference, hip circumference etc.
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1.6 The Study Encountered the Following Limitations
i. Inability to trace academic records of some students who had already participated in the study.
ii. Lack of complete academic records of some students.
iii. Lack of co-operation by some school authority.
iv. Limited time were allocated for the study by the schools authorities, thereby making it difficult to get the required number of students.
v. Different subjects combinations of some students, as some students who participated in the studies do not offer some of the general subjects under the consideration.
vi. Loss of questionnaires.
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