question: Is a child's desire to play with trucks vs dolls a learned behavior or an instinctual behavior?
comment: At the ELI5 level: we don't know for sure. The most likely answer is "some of both". The intersection of sex, gender, culture, development and education is a complex area that is the subject of active study by multiple scientific fields. There are some specific things we can say. We can say, for example, that there's no instinctual behavior with regard to "trucks" because trucks simply haven't been around long enough. But there might be some other elements involved - for example, maybe some children are genetically predisposed to bright colors while others aren't, and maybe truck toys are predominantly in bright colors.
passages: Girls with congenital adrenal hyperplasia (CAH) have atypically high blood concentrations of testosterone. In studies of toy preference, these girls show increased interest in male-typical toys, like trucks and balls. Overall, their play habits and preferences more closely resembled male-typical play than female-typical play. Even with children exposed a normal range of prenatal androgens, increased testosterone was associated with increased preference for male-typical toys, and decreased prenatal testosterone was associated with greater interest in female-typical toys.
   Overall, the degree of androgen exposure during prenatal and postnatal development may bias males and females toward specific cognitive processes, which are further reinforced through processes of socialization. The male interest in balls and wheeled toys may relate to the androgenised brains preference for objects that move through space. The higher levels of androgens in the developing male brain could elicit greater attraction to cars and balls, while lower levels of androgens elicit a preference for dolls and nurturing activities in the female brain.
   It has been noted by researchers that, "Children as young as 18 months display sex-stereotyped toy choices". When eye movement is tracked in young infants, infant girls show a visual preference for a doll over a toy truck (d  1.0). Boys showed no preference for the truck over the doll. However, they did fixate on the truck more than the girls (d = .78). This small study suggests that even before any self-awareness of gender identity has emerged, children already prefer sex-typical toys. These differences in toy choice are well established within the child by the age of three.
   Toy soldiers, perhaps a precursor to modern action figures, have been a popular toy for centuries. They allow children to act out battles, often with toy military equipment and a castle or fort. Miniature animal figures are also widespread, with children perhaps acting out farm activities with animals and equipment centered on a toy farm.
  
  Section::::Types.:Vehicles.
   An example of a correct answer would be if the child and the doll were situated on the complete opposite sides of the mountain model with a tree on the child’s side and a large mountain in the middle acting as a visual barrier. A preoperational child would claim that the doll could see the tree, whereas the concrete operational child would select a photograph without the tree since the mountain is large enough to block the tree from the doll’s view. A concrete operational child would pass the Three Mountain Problem task.
  
  Section::::Follow Up Studies.
   The aim in this study was to examine ASD children's reactions to various mechanical toys including remote-controlled robots and mechanized animal toys to determine which features lead to increased social interaction between the mechanical toy and the child and ASD children's interaction with a typically developing (TD) peer in the context of the different mechanical toys. The Focus Foundation sought to extend the results from a single child interacting with these mechanical toys to interactions between two children while engaging with the toys. Shared play was observed in the context of a variety of different robots and/or mechanized animals to see what increased social engagement behaviors.
   After the confederate left the room, the children were given the opportunity to individually interact with similar toys. Children who observed the non-aggressive confederate's behavior played quietly with the toys and rarely initiated violence toward the Bobo doll. Children who watched the aggressive confederate were more likely to imitate the confederate's behavior by hitting, kicking, and shouting at the Bobo doll.
  
  Section::::Factors influencing behavioral modeling.
  
  Section::::Factors influencing behavioral modeling.:Psychological factors.
  
  Bandura proposed that four components contribute to behavioral modeling.
  
  BULLET::::1. Attention. The observer must watch and pay attention the behavior being modeled.
   Even for toys that don't possess explicit educational value, a thoughtful parent or teacher can turn a static figurine, for example, into an object of interest, by pointing out its features or costumes, or referring to its history or science (e.g., a figurine of a Native American may be a starting point for exploring American history; a Santa Claus may be used to explore the roots of Christmas; a toy astronaut to explore science...), which can be done in conjunction with a more-explicitly "edutaining" object, such as a picture book. Most children are naturally inquisitive (possibly why they sometimes break their toys; simply to know what is inside or how it moves or what produces that sound), and caregivers should not waste this opportunity.
   Dolls also mediated the transition between childhood and adulthood in the Yup'ik shamanism. The centrality of play dolls in the lives of Yup'ik girls is evident from the role they assumed as the markers of seasons and life cycles. There was a strict rule against taking a doll outside during winter and breaking it was thought to bring endless cold and storms.
  
  Section::::History.
   Construction toy play is beneficial for building social skills and building trust in others because it acts as a collaborative task where individuals have to cooperate in order to finish the task — building an object out of Lego, for example. The effect was found in high school students.
  
  For children specifically, children who complete models using toy building blocks have much better spatial ability than children who do not complete such models. Spatial ability also predicts completion of models.
   The concept of behavioral modeling was most memorably introduced by Albert Bandura in his famous 1961 Bobo Doll Experiment. In this study, 72 children from ages three to five were divided into groups to watch an adult confederate interact with an assortment of toys in the experiment room, including an inflated Bobo doll. For children assigned the non-aggressive condition, the confederate ignored the doll. For children assigned the aggressive condition, the confederate spent the majority of the time physically aggressing the doll and shouting at it.
   Most vehicles were of a small 'Matchbox' or 'Tootsietoy' size, but a few were larger 'Tonka' like dump trucks, tractors and other construction vehicles.
  
  Typical of an early diecasting firm, also made were sundry diecast buildings, road signs, doll house furniture pieces and yard working shovels, pitchforks, rakes and other implements. Some of the larger toys and doll house accessories were apparently tooling from Tri-Ang of England as the Tri-Ang name appears with the clown and Fun Ho! logo on some toys (Fun Ho! 2015).
   Construction toy play is also beneficial for autistic children when both individual and group play with building blocks is incorporated. Autistic children who played with building blocks were motivated to initiate social contact with children their age, they were able to maintain and endure contact with those children, and autistic children were also able to surpass the barriers of being withdrawn and being highly structured.
  
  Section::::Influence on architecture.
   Infant boys and girls as young as 9 months old have been found to display stereotypical toy preferences, suggesting that there are biological and environmental factors which appear very early in development. A City, University of London study found that in children aged 9 to 32 months, boys preferred balls and toy cars, and that the preference increased with age.
   In some cultures, societies utilize toys as a way to enhance a child's skillset within the traditional boundaries of their future roles in the community. In Saharan and North African cultures, play is facilitated by children through the use of toys to enact scenes recognizable in their community such as hunting and herding. The value is placed in a realistic version of development in preparing a child for the future they are likely to grow up into. This allows the child to imagine and create a personal interpretation of how they view the adult world.
   However, in other cultures, toys are used to expand the development of a child's cognition in an idealistic fashion. In these communities, adults place the value of play with toys to be on the aspirations they set forth for their child. In the Western culture, the Barbie and Action-Man represent lifelike figures but in an imaginative state out of reach from the society of these children and adults. These toys give way to a unique world in which children's play is isolated and independent of the social constraints placed on society leaving the children free to delve into the imaginary and idealized version of what their development in life could be.
   Lobel & Menashri (1993) explores how the rigidity of gender schemas guides behavior. The population of interest consisted of preschool children selected from three different preschools in Tel-Aviv, Israel, and the study focused on the relationship between the children's gender-typed toy choice, their frameworks regarding cross-gender behavior, and their concepts of gender constancy. During the procedure, two feminine and two masculine toys were presented to individual children: a visibly new doll, a tattered, old doll, a shiny new truck, and an old, faded truck. Based on a pretest, the dolls and trucks were clearly recognized as feminine and masculine, as well as attractive and unattractive based on their quality. All children preferred the new toy when presented with a pair of singularly gendered toys. Children were first given a toy preference test, then a gender constancy interview, and then a gender-role norms interview. The results indicate that children with a more flexible view on gender-role norms made fewer gender-typed choices than children with rigid norms. Similarly, for children with more flexible gender norms, attractiveness of the toy proved to be more strongly related to preference than the toy's adherence to a traditional gender-role. This result begs the question: from where does this flexibility in gender behavior come? The authors favor the explanation that parental norms play a large role, but insist that further research must be done. Echoing Serbin et al. (2001), they also assert that a certain level of cognitive ability must be reached in order to demonstrate flexibility in gender roles, otherwise conceptions of fundamental gender constancy could become confused with external objects associated with a traditional gender role.
   "Vroom" is cited in early childhood language development texts as an example of a common early word or sound made by young children in the course of play. Anthony D. Pellegrini writes in the chapter "Interpreting Children's Play" in the book "The Puzzling Child: From Recognition to Treatment" (1982):
  
  The social phonological play of two year olds is exemplified by use of conventional noises, through syllable repetition, to identify actions, events, and objects...Two children may be playing parallel or associatively with trucks. Their phonological play would be the "vroom" sound of truck engines
   On the subject of congenital adrenal hyperplasia, Fine presents the argument of correlation being confused for causality; are females with CAH interested in typically masculine activities due to their having an innate quality or is this a result of their association with boys and men as a gender? If a visual and spatial value is deemed as a preeminent element in typically masculine toys (such as trucks), females with CAH and males in studies should consequently show a much higher interest for neutral toys such as puzzles and sketchpads (as opposed to non-CAH females), something which they do not.
   Children have played with miniature versions of vehicles since ancient times, with toy two-wheeled carts being depicted on ancient Greek vases. Wind-up toys have also played a part in the advancement of toy vehicles. Modern equivalents include toy cars such as those produced by Matchbox or Hot Wheels, miniature aircraft, toy boats, military vehicles, and trains. Examples of the latter range from wooden sets for younger children such as BRIO to more complicated realistic train models like those produced by Lionel, Doepke and Hornby. Larger die-cast vehicles, 1:18 scale, have become popular toys; these vehicles are produced with a great attention to detail.
   One of the earliest signs of gender differences in play patterns is the appearance of gender-segregated play groups and toy preferences. Boys tend to be more "rough and tumble" in their play while girls shy away from this aggressive behavior, leading to the formation of separate play groups. Calvert 2013 In addition, boys tend to gravitate more towards toys such as trucks while girls tend to gravitate towards dolls, but these preferences are not absolutes. A study by Alexander, Wilcox, and Woods showed that female infants showed more visual interest in a doll over a toy truck while male infants showed more visual interest in a toy truck over a doll, but these differences were more pronounced in the females. This study suggests that preferences for feminine or masculine toys precede any sex differences in the perceptual features of such toys, leading to the assumption that gender-based toy preference is innate.
   Boys' toys and games
  
  Boys' toys and games, as opposed to girls' toys and games, are a subset of toy and games that appeal to male children. Research suggests that this appeal may be driven by biological factors, peer pressure, parental choices, marketing, or tradition.
  
  Section::::Background.
  
  Research suggests that there may be some biological predispositions at play that drive toy preferences. Kim Wallen, a psychologist at Yerkes National Primate Research Center, found in her study that male rhesus monkeys played with model dump trucks and other wheeled toys, over plush dolls.
   The individual engages in the behavior to obtain attention from another person. For example, a child throws a toy because it characteristically results in a parent's attention. (If this behavior results in a parent looking at child and giving them lots of attention—even if they're saying "NO"—he will be more likely to engage in the same behavior in the future to get a parent's attention.) Common forms of attention include, but are not limited to, hugs, kisses, reprimands, frowns, smiles, etc.
  
  "Access to tangibles (positive reinforcement: tangible/activity)":
   Bonnie and her mother are on a road trip to visit Bonnie's grandmother; Bonnie has brought Woody, Buzz Lightyear, Jessie, Rex, Mr. Pricklepants, Mr. Potato Head, and Trixie with her. In the trunk of the vehicle, the toys are watching a horror film on a portable DVD player. When the car gets a flat tire, Bonnie and her mother must spend the night at the Sleep Well roadside motel, as a tow truck cannot be sent out until the next morning.
   Toys are often employed in the context of mimicry and roleplay to partially experience personalities or situations not otherwise possible, very akin to simulation in video games. They can be used as primitive means to nurture an instinct or a character trait in children. Often, toys work simultaneously the other way, providing children with the means to "express" those things: a doll may be used by a girl to mimic her mother or express motherhood as much as to explore it.
  