There are other differentiating factors there that could lead to the preference choice that are not related to whether something is mechanical in nature. Thing

There are other differentiating factors there that could lead to the preference choice that are not related to whether something is mechanical in nature. Things like color, texture, etc. have been shown to have strong biases between the sexes. A possible control they did not employ during the study would be to have a series of toys that were identical in all ways except color, for example. Also *very* worth noting: As shown in their Fig. 1, when play time with toys is examined in human children (Berenbaum and Hines,1992) and rhesus macaques of all ages, males spend significantly more of their play time with the “male” toy(s) than with the female toy(s), while females spend about equal times with “male” and “female” toys. This is true both for frequency of interactions and in time spent playing (Hassett et al., 2008). **Therefore, one key difference between males and females in these studies is that males actually show a toy preference while females do not!** (Emphasis mine)