Table 2.
Number and percent of non-right-handers (NRH) and right handers (RH) by sample and sex for four handedness direction indicators
| Twins | Singletons | Total | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Handedness Direction | Male n (%) |
Female n (%) |
χ2(df = 1) | Male n (%) |
Female n (%) |
χ2(df = 1) | Twins n (%) |
Singletons n (%) |
χ2(df = 1) |
| Writing hand | |||||||||
| NRH | 17 (9.1%) | 14 (7.1%) | 0.51 | 19 (8.6%) | 14 (6.9%) | 0.46 | 31 (8.1%) | 33 (7.8%) | 0.02 |
| RH | 170 (90.9%) | 183 (92.9%) | 201 (91.4%) | 190 (93.1%) | 353 (91.9%) | 391 (92.2%) | |||
| Drawing hand | |||||||||
| NRH | 26 (13.9%) | 21 (10.7%) | 0.94 | 27 (12.3%) | 29 (14.2%) | 0.35 | 47 (12.2%) | 56 (13.2%) | 0.17 |
| RH | 161 (86.1%) | 176 (89.3%) | 193 (87.7%) | 175 (85.8%) | 337 (87.8%) | 368 (86.8%) | |||
| EHI2 | |||||||||
| NRH | 13 (7.0%) | 12 (6.1%) | 0.12 | 20 (9.1%) | 16 (7.8%) | 0.21 | 25 (6.5%) | 36 (8.5%) | 1.13 |
| RH | 174 (93.0%) | 185 (93.9%) | 200 (90.9%) | 188 (92.2%) | 359 (93.5%) | 388 (91.5%) | |||
| PegQ2 | |||||||||
| NRH | 23 (12.1%) | 29 (14.2%) | 0.38 | 40 (18.1%) | 25 (12.2%) | 2.87 | 52 (13.2%) | 65 (15.3%) | 0.71 |
| RH | 167 (87.9%) | 175 (85.8%) | 181 (81.9%) | 180 (87.8%) | 342 (86.8%) | 361 (84.7%) | |||
1) For the binary classification of ‘writing hand’ and ‘drawing hand’, NRH includes both left-hand preference and no preference
2) EHI2 and PegQ2 are the binary classification of EHI and PegQ scores respectively, using zero as the cutoff point. NRH refers to those who scored less or equal to zero. There are 4 participants (including 1 twin and 3 singletons) who scored exactly zero on EHI