Hassett Key Study PDF

HASSETT ET AL. (MONKEY TOY PREFERENCE) AIMS 1. To test if sex differences in children’s toy preferences result from biological factors, for example from prenatal hormone exposure rather than through socialisation. 2. To investigate if male and female rhesus monkeys have similar toy preferences...

HASSETT ET AL. (MONKEY TOY PREFERENCE) AIMS 1. To test if sex differences in children’s toy preferences result from biological factors, for example from prenatal hormone exposure rather than through socialisation. 2. To investigate if male and female rhesus monkeys have similar toy preferences to human infants, despite no socialisation experience with human toys. RESEARCH METHODOLOGY Hassett et al. is an experiment as the researchers were looking for a causal relationship between the monkeys’ sex and their toy preferences. The monkeys were observed in their normal enclosure. This was a natural environment for them, as they had all been living together at the research centre for 25 years. However, the researchers were able to control this environment, by keeping the monkeys indoors while positioning the toys. The data was collected using observation, through analysis of video recordings of the monkeys in their outdoor enclosure. Design and variables The design was independent measures as two groups of monkeys were compared: males and females. Sex is a naturally occurring independent variable, determined by the appearance of the external sex organs. The dependent variable was whether the monkeys interacted more with the plush toys or the wheeled toys. Seven trials were completed, each with a different pair of toys. When the monkeys interacted with the toys, their social rank and age were recorded. Social rank had already been determined by observing grooming behaviour; the monkey doing the grooming is always subordinate than the monkey being groomed. Sample 135 monkeys at the Yerkes National Primate Research Center Field Station. The troop included infant and adult monkeys. 14 of the monkeys had previously participated in research on prenatal hormones so they were not included in the current study. 39 babies were not included as it was hard to tell them apart and therefore identify their sex. Of the remaining monkeys (61 females and 21 males), 34 interacted with the toys on more than five occasions (23 females and 11 males) and were included in the analysis. PROCEDURE Seven 25-minute observations were completed in the outdoor area of the monkey enclosure at the research centre. Before each observation, the observers positioned a pair of toys (one wheeled, one plush) in the outdoor area while the monkeys waited indoors. Toys were always placed 10 m apart and the positions were counterbalanced- wheeled toys on the right and plush on the left in half of the trials and vice versa on the remaining trials. This ruled out the possibility that the monkeys preferred a certain area of the enclosure rather than genuinely preferring the properties of the toy that they found there. The toys varied in size, shape and colour and were selected according to what you could ‘do’ with them rather than simply choosing traditional ‘male’ or ‘female’ toys. There were six wheeled toys: wagon, truck, car, construction vehicle, shopping cart and dump truck, ranging from 16 to 46 cm, and seven plush toys: Winnie-the-Pooh, Raggedy-Ann, Scooby- Doo and four soft toy animals, including a koala, armadillo, teddy and turtle, ranging from 14 to 73 cm. A video camera was focused on each toy so that all interactions could be recorded for later analysis. Two observers watched the videos and used a behavioural checklist to code every interaction between the monkeys and the toys. Using an app called Handobs, the observers recorded their data using palm pilots. They recorded the start and finish times of each interaction and calculated the duration in seconds. The checklist included: extended touching, holding, sitting on, dragging, carrying and manipulating the toys, as well as briefly touching, sniffing, mouthing, destroying, jumping away from and throwing them. Ambiguous behaviours were discussed until the observers agreed on how to code the interaction. For each interaction, the observers also recorded the monkey’s age, rank and sex. RESULTS The observers calculated average frequencies and durations for each behaviour by adding up the totals and dividing by the number of trials each monkey participated in. Monkeys with fewer than five behaviours were discounted (3 males and 14 females). Next, the researchers calculated the total number and total duration of interactions with each toy type (plush versus wheeled) by adding up the averages for each individual behaviour. Overall, most of the monkeys did not interact with the toys at all. Those that did often only interacted for a few seconds, while a small number of monkeys interacted much more and for much longer periods of time. Male monkeys preferred wheeled toys Male monkeys' preferred wheeled toys (mean=9.77), compared with plush toys (mean=2.06). They also played less with plush toys compared with females. 73% of the males preferred wheeled toys, 9% preferred plush toys and 18% showed no significant preference. These preferences did not appear to be affected by age or rank. Female monkeys show no consistent preference Although females showed some preference for the plush toys (mean=7.97) compared with the wheeled toys (mean=6.96), the difference was not significant. There was also no significant difference between the males and females in terms of frequency of wheeled toy play. Only 30% of the females preferred the plush toys, 39% preferred the wheeled toys and 30% showed no significant preference for either toy. Females with no preference ranked significantly lower in the social hierarchy than females who preferred plush toys but there was no significant difference in rank between females who preferred wheeled versus plush toys. Duration of interactions When the females played with wheeled toys, they did not play with them for as long as the males (1.27 min compared with 4.76 min) and they also played longer with the plush toys than the males did (1.49 min compared with 0.53 min). Males played significantly longer with wheeled than plush toys but the standard deviation for the duration of wheeled toy play was relatively large compared with the females (7.59 compared with 2.2). This suggests that some of the males played considerably longer with the wheeled toys than others. The females showed even greater individual differences with regard to time spent engaged in plush toy play- some individuals played longer with these toys; others interacted with them more briefly. Overall, there was no significant difference in time spent interacting with either plush (1.49 min) or wheeled toys (1.27 min) for the female monkeys. Social rank and toy preference When the data from both sexes was combined, there was a significant positive correlation between social rank and frequency of interaction for both types of toy. Higher-ranking monkeys interacted more with the toys. Interestingly, when the data from females was examined more closely, the researchers found that the higher the rank, the more time females spent interacting with plush toys. This was not true for wheeled toys. CONCLUSIONS Based on their observations and comparisons with human infants. Hassett et al. concluded that sex-typed toy preferences in humans may result from biological sex differences, as their observations suggest that rhesus monkeys show similar preferences to human infants, even without clear gender differences in socialisation. They concluded that human toy preferences, as with the monkeys, ‘reflect hormonally influenced behavioural and cognitive biases’ which interact with learning experiences within the social environment.