Correction to: Scientific Reports https://doi.org/10.1038/s41598-020-76649-3, published online 12 November 2020


The original version of this Article contained errors due to the miscalculation of the winning rates.


Firstly, the data presented in Figure 2 was incorrect. As a result, in panel A, “R2 = 0.55” was corrected to “R2 = 0.72”; in panel B, “R2 = 0.57” was corrected to “R2 = 0.74”; and in panel C, “R2 = 0.41” was corrected to “R2 = 0.61” and “R2 = 0.64”.


In panel D, the Table:

 

Eye span

Body length

male-male

0.55

0.35

female-female

0.57

0.46

male–female

0.41

0.29

female-male

0.41

0.29


now reads:

 

Eye span

Body length

male-male

0.72

0.49

female-female

0.74

0.59

male–female

0.64

0.48

female-male

0.61

0.40


As a result, the legend of Figure 2,


“Flies with relatively long eye spans are likely to be winners in contests. Winning rates in 100 [(A) male vs. male], 140 [(B) female vs. female] and 88 [(C) male vs. female] contests including more than 10 games for pairs of randomly chosen individuals with different eye-span lengths were measured and analysed in regard to their relationship with the eye-span ratio (own eye span/opponent’s eye span). Because the rates of both the winner and loser in a contest are simultaneously shown in the same coordinate system, the scatter of the data points shows symmetry around the origin. Thus, to focus on only one player in all contests, ignore values less than 1.0 on the abscissa or less than 0.5 on the ordinate. Only one data point in (A), for which the eye-span ratio is 2.15, was excluded as an outlier. Solid lines were drawn by sigmoid approximation via the Gauss–Newton algorithm (Minitab 16, Minitab Inc.). R2 = 0.55 (A), 0.57 (B), 0.41 [males in (C)], and 0.41 [females in (C)]. Broken lines indicate 95% confidence intervals. The P values of the three approximation lines are all less than 0.001, indicating significant fits. The P value from the ANCOVA of the datum point distribution among the three kinds of sexual combinations was 0.9998, indicating a non-significant difference.”


now reads:


“Flies with relatively long eye spans are likely to be winners in contests. Winning rates in 100 (A, male vs. male), 140 (B, female vs. female) and 88 (C, male vs. female) contests including more than 10 games for pairs of randomly chosen individuals with different eye-span lengths were measured and analysed in regard to their relationship with the eye-span ratio (own eye span/opponent’s eye span). Each datum point represents one player’s outcome in a contest on one pair of flies with different eye spans. A single contest generates two data points: one for long-eyed fly and the other for short-eyed fly. Because all the winning rates included draws in the denominator, the mean values in each sexual combination are less than 0.5. Only one data point in A, for which the eye-span ratio is 2.15, was excluded as an outlier. Solid lines were drawn by sigmoid approximation via the Gauss-Newton algorithm (Minitab 16, Minitab Inc.). R2 = 0.72 (A), 0.74 (B), 0.64 (males in C), and 0.61 (females in C). Broken lines indicate 95% confidence intervals. The P values of the three approximation lines are all less than 0.001, indicating significant fits. The P value from the ANCOVA of the datum point distribution among the three kinds of sexual combinations was 0.9469, indicating a non-significant difference.”


The original Figure 2 and accompanying legend appear below.

Figure 2
figure 2

Flies with relatively long eye spans are likely to be winners in contests. Winning rates in 100 [(A) male vs. male], 140 [(B) female vs. female] and 88 [(C) male vs. female] contests including more than 10 games for pairs of randomly chosen individuals with different eye-span lengths were measured and analysed in regard to their relationship with the eye-span ratio (own eye span/opponent’s eye span). Because the rates of both the winner and loser in a contest are simultaneously shown in the same coordinate system, the scatter of the data points shows symmetry around the origin. Thus, to focus on only one player in all contests, ignore values less than 1.0 on the abscissa or less than 0.5 on the ordinate. Only one data point in (A), for which the eye-span ratio is 2.15, was excluded as an outlier. Solid lines were drawn by sigmoid approximation via the Gauss–Newton algorithm (Minitab 16, Minitab Inc.). R2 = 0.55 (A), 0.57 (B), 0.41 [males in (C)], and 0.41 [females in (C)]. Broken lines indicate 95% confidence intervals. The P values of the three approximation lines are all less than 0.001, indicating significant fits. The P value from the ANCOVA of the datum point distribution among the three kinds of sexual combinations was 0.9998, indicating a non-significant difference.


Consequently, the values present in the Results section, under the subheading ‘Hypothesis 1: Eye span as an honest signal to inform opponents of fighting capacity’, were incorrect. As a result,


“The coefficient of determination representing the correlation was 0.55. Similar striking correlations were also found in contests between females (Fig. 2B) and in contests between males and females (Fig. 2C), with winning rates for longer-eyed individuals of 85% (P value = 6.3 × 10–18) in female-female contents and 78% (P value = 5.4 × 10–8) in male–female contents and coefficients of determination of sigmoid fitting curves of 0.57 and 0.41, respectively. In the contests between males and females, neither sex was more likely to win. The fitted curves for these three kinds of sexual combinations were very similar and indistinguishable by covariance analysis. Based on these results, it appears that this species participates in contests in which eye span acts as an honest signal of fighting capacity that informs the opponent similarly in all three kinds of sexual combinations. However, among the contests in which the difference between the eye spans of both individuals was small (less than 10%), the male-male contest displaying the winning rate of around 50% (more than 40% and less than 60%) showed a higher percentage than contests of other sexual combinations (32% in male-male contents, 16% in female-female contests, and 10% in male–female contests). This might suggest a tendency for males to not readily give up during a game.”


now reads:


“The coefficient of determination representing the correlation was 0.72. Similar striking correlations were also found in contests between females (Fig. 2B) and in contests between males and females (Fig. 2C), with winning rates for longer-eyed individuals of 85% (P value = 6.3 × 10–18) in female-female contents and 78% (P value = 5.4 × 10–8) in male–female contents and coefficients of determination of sigmoid fitting curves of 0.74 and 0.61–0.64, respectively. In the contests between males and females, neither sex was more likely to win. The fitted curves for these three kinds of sexual combinations were very similar and indistinguishable by covariance analysis. Based on these results, it appears that this species participates in contests in which eye span acts as an honest signal of fighting capacity that informs the opponent similarly in all three kinds of sexual combinations. However, among the contests in which the difference between the eye spans of both individuals was small (less than 10%), the male-male contest displaying the winning rate of around average 41.9% (more than 31.9% and less than 51.9%) showed a higher proportion than contests of other sexual combinations (26% in male-male contents, 13% in female-female contests, and 14% in male–female contests). This might suggest a tendency for males to not readily give up during a game.”


In addition, the data in Tables ‘Estimated values of parameters’ and ‘Coefficient of determination’, present in the Supplementary Information, Section 3: ‘Statistical method for fitting sigmoid curves to the relationship between winning rate and eye-span ratio between players’ was incorrect. The correct and incorrect values appear below. The original Supplementary Information is provided below.


Incorrect:


Estimated values of parameters:

 

Regression coefficient

Estimate

Standard error

95% Confidence intervals

Male vs male

Theta1

0.752089

0.0297833

(0.697686, 0.828404)

Theta2

0.247911

0.0297833

(0.171596, 0.302314)

Theta3

− 0.000000

0.0254107

(− 0.052998, 0.052998)

Theta4

0.083989

0.0234799

(0.042551, 0.153038)

Female vs female

Theta1

0.769293

0.0257683

(0.722399, 0.825377)

Theta2

0.230707

0.0257683

(0.174623, 0.277601)

Theta3

0.000000

0.0205945

(− 0.041031, 0.041031)

Theta4

0.076302

0.0172004

(0.047411, 0.116102)

Males in male vs female

Theta1

0.816198

0.0978977

(*, 1.35182)

Theta2

0.214554

0.0869185

(‐0.146609, 0.34818)

Theta3

0.032999

0.0924641

(− 0.168222, 0.33956)

Theta4

0.156657

0.0819604

(0.056978, 0.57010)

Females in male vs female

Theta1

0.785446

0.0869185

(0.651821, 1.14661)

Theta2

0.183802

0.0978977

(− 0.351816, *)

Theta3

− 0.032999

0.0924640

(− 0.339557, 0.16822)

Theta4

0.156657

0.0819603

(0.056978, 0.57010)


Coefficient of determination:

 

Factors

DF

Square sum

Mean square

F-value

p-value

Male vs male

Regression

1

8.3362

8.3362

246.27

 < 0.001

Residual error

198

6.7022

0.0338

  

Sum

199

15.0384

   

Coefficient of determination: 8.3362/15.0384 = 0.554

Female vs female

Regression

1

13.971

13.971

372.46

 < 0.001

Residual error

278

10.428

0.038

  

Sum

279

24.399

   

Coefficient of determination: 13.971/24.399 = 0.573

Males in male vs female

Regression

1

7.111

3.9105

60.24

 < 0.001

Residual error

86

4.056

0.0649

  

Sum

87

11.167

   

Coefficient of determination: 3.9105/9.4934 = 0.412

Females in male vs female

Regression

1

3.9105

3.9105

60.24

 < 0.001

Residual error

86

5.5828

0.0649

  

Sum

87

9.4934

   

Coefficient of determination: 3.9105/9.4934 = 0.412


Correct:


Estimated values of parameters:

 

Regression coefficient

Estimate

Standard error

95% Confidence intervals

Male vs male

Theta1

0.740116

0.0220877

(0.697420, 0.788496)

Theta2

0.133642

0.0215938

(0.087323, 0.175114)

Theta3

0.006398

0.0132290

(− 0.019918, 0.033322)

Theta4

0.055613

0.0120333

(0.032345, 0.087582)

Female vs female

Theta1

0.759356

0.0197601

(0.721084, 0.801000)

Theta2

0.107508

0.0190800

(0.068658, 0.143590)

Theta3

0.009126

0.0114918

(− 0.013435, 0.032022)

Theta4

0.052528

0.0093982

(0.034393, 0.073573)

Males in male vs female

Theta1

0.801408

0.0611882

(*, 0.943666)

Theta2

0.089077

0.0542438

(− 0.0277675, 0.183084)

Theta3

0.051497

0.0439795

(− 0.0402507, 0.139824)

Theta4

0.106692

0.0368689

(0.0566858, 0.188948)

Females in male vs female

Theta1

0.788780

0.0673040

(*, 0.939862)

Theta2

0.048852

0.0673549

(− 0.123703, 0.161645)

Theta3

− 0.008878

0.0525570

(− 0.121066, 0.095168)

Theta4

0.127686

0.0439338

(0.069573, 0.237555)


Coefficient of determination:

 

Factors

DF

Square sum

Mean square

F-value

p-value

Male vs male

Regression

1

14.079

14.0795

518.92

 < 0.001

Residual error

198

5.372

0.0271

  

Sum

199

19.452

   

Coefficient of determination: 14.0795/19.452 = 0.724

Female vs female

Regression

1

23.568

23.5684

777.13

 < 0.001

Residual error

278

8.431

0.0303

  

Sum

279

31.999

   

Coefficient of determination: 23.5684/31.999 = 0.737

Males in male vs female

Regression

1

7.111

7.11071

150.78

 < 0.001

Residual error

86

4.056

0.04716

  

Sum

87

11.167

   

Coefficient of determination: 7.11071/11.167 = 0.637

Females in male vs female

Regression

1

6.904

6.90449

136.56

 < 0.001

Residual error

86

4.348

0.05056

  

Sum

87

11.253

   

Coefficient of determination: 6.90449/11.253 = 0.614


The original Article and accompanying Supplementary Information file have been corrected.