Hasset et al (Monkey Toy Preferences) Flashcards
AIM:
The aim of the study was to investigate whether toy preferences in monkeys resemble those in children, in order to test whether sex differences in toy choices are biologically determined.
SAMPLE:
The participants were 21 males and 61 female rhesus monkeys living at the Yerkes primate research center in the USA.
BACKGROUND:
A model is nothing more than a representation of a phenomenon, often on a smaller or simpler scale. In the case of human development, a simpler model is needed, and one that offers the opportunity to control experiences. Higher primates, closely related to humans genetically, and with some very similar behaviours, can provide such a model. By looking at primate models of human behaviour it may be possible to see whether gender differences in behaviour could be caused by biological rather than social differences.
PROCEDURE: 1
The toys were divided into two categories. The category of “wheeled toys” matched vehicle toys, typically for boys, and “plush toys” matched typically for girl’s toys. The toys varied in terms of size, shape and colour.
PROCEDURE: 2
For each social group, seven trials, each lasting 25 minutes, were observed using two video cameras. Each trial began with all the monkeys in the group indoors while one plush toy and one wheeled toy were placed 10 metres apart in the outdoor enclosure. One video recorder was directed towards each toy and the plush and wheeled toys were counterbalanced between left and right locations on each trial.
After each trial the toys were removed and the video tape was analysed by two observers working together to reach a consensus. They identified each animal interacting with a toy and coded specific activities directed towards the toys using a behavioural checklist. The exact time at which each activity occurred was also recorded.
PROCEDURE: 3
To analyze the data, the records for each behaviour for each animal were converted into an overall average frequency and duration for that individual. This was because each animal could have participated in a different number of activities in different trials.
RESEARCH METHOD:
This was a field experiment as the environment in which the participants were tested was their normal, outdoor housing area and they were free to interact with the toys or not.
EXPERIMENTAL DESIGN and VARIABLES:
The experimental design was independent measures as the independent variable was gender; each animal being recorded was either male or female. Observations were used as a technique to measure the dependent variable of activities with the toys.
RESULTS: 1
Comparisons were made between males and females and between each gender’s preference for wheeled or plush toys.
Statistical analyses comparing toy preferences within each sex, using frequency data, found that males preferred wheeled compared to plush toys but that females did not show a preference for plush toys over wheeled toys. A comparison between the sexes, again using frequency data, also found that females interacted with plush toys more than males, but there was no sex difference for wheeled toys.
In comparisons of the duration data, males interacted a longer time in total with wheeled toys than with plush toys. However, the females played for a similar total length of time with wheeled and plush toys.
RESULTS: 2
Even though the difference in play durations for the male monkeys was big enough to show a significant difference between time spent playing with wheeled and plush toys, no significant difference was found in a between- sex comparison. This means that there was no overall difference between the time that males and females spent playing with the wheeled and plush toys.
Further comparisons were made to calculate ‘magnitude of preference’, that is, how much males preferred the ‘masculine’ (wheeled) toy and how much females preferred the ‘feminine’ (plush) toy. For males, this was calculated by taking the difference “total frequency of wheeled toy interaction - total frequency of plush toy interaction. For females, the equation ‘total frequency of plush toy interaction total frequency of wheeled toy interaction’ was used. The same type of comparison was also performed on the duration scores. Statistical analysis of these differences confirmed that male monkeys had a higher preference for ‘masculine’ (wheeled) toys than female monkeys had for the ‘feminine’ (plush) toys.
RESULTS: 3
Differences between the sexes were still evident when the data was re-examined taking into account the social ranks of the individuals. Furthermore, correlations were also conducted on the results to look for relationships between individual monkeys’ ranks within the social hierarchy and the frequency or duration of activities with each toy type for males and females combined, rank and total frequency of interactions were positively correlated for the wheeled toy and for the plush toy. Using just the data for males, neither frequencies nor durations correlated with rank. For females, however, rank was positively correlated with frequency of interactions for the wheeled toy and for the plush toy, although rank only correlated with duration for the plush toy, not the wheeled toy. As this shows that rank may be related to toy interactions in females but not in males, it is unlikely that social rank is responsible for the sex differences in toy preference overall. Furthermore, although the sample size was too small for a detailed analysis of the results by age, comparisons were possible between wider groups. A comparison between juvenile, sub-adult, adult and old animals did not differ in terms of frequency or duration for either toy type.
CONCLUSION:
🔹Males monkeys have a strong preference for masculine toys, similar to male human children.
🔹Female monkeys are variable in their toy preferences, similar to female human children.
🔹Male monkeys preferred wheeled toys more than female monkeys preferred plush toys.
🔹Hassett et al. argue that their findings support a biological explanation for toy preferences. These preferences develop in the absence of socialisation because hormonal differences can be responsible for differences in their development, and not social ones.
(Importantly, such biologically driven differences could interact with social pressures on children. Boys choosing girls’ toys tend to receive more negative responses than girls choosing boys’ toys. This would reinforce a pre-existing biological tendency for boys to be more masculine in their toy choices and for girls to remain more variable in their choices)
EVALUATION (STRENGTHS):
- High Validity - A key strength of this study was the use of animals to eliminate the effect of socialisation (eliminate the effects of social interactions on the individual being studied). This was taken further, to exclude extraneous variables that could affect social interactions such as age and social rank. The age of individuals was known as the monkey group had been established for over 25 years. Social rank had been assessed through behavioural observations of who groomed whom, dominance behaviours and submissive behaviours.
- High Reliability - The observation process was highly standardized, for example with clear definitions of behaviour to improve reliability. The trials were of a standard length of 25 minutes. They identified each animal interacting with a toy and coded specific activities directed towards the toys using a behavioural checklist. The exact time at which each activity occurred was also recorded.
⬆️copied from procedure
EVALUATION (WEAKNESSES):
🔹 Low Validity -
A weakness of the study was that there were some differences in the way that the monkeys and the children were compared. For example, the masculine and the feminine toys offered to the monkeys were chosen for their object properties rather than because they were gender-stereotyped toys for children. The children were assessed in a different study using different toys and only duration of play was measured, not frequency. Furthermore, the most significant comparison was frequency rather than duration between both. This reduces the validity of the study.
🔹Low Generalizability -
The sample only represents rhesus monkeys, and therefore, the findings cannot be applied to other species of monkeys who may show differences in preferences. Although the sample comprised of 21 males and 61 females, the results analysed were eventually of only 11 males and 23 females, which lowers the generalisability considerably.
ETHICAL ISSUES:
The study was conducted following appropriate ethical guidelines for the care of animals in the USA and was approved by the Emory University Ethical committee on animal care and use.
In terms of feeding, the animals received regular and appropriate food (twice daily monkey feed plus daily fruit and vegetables) and had constant access to water. They were ethically housed in family groups, in large enclosures, with access to both a temperature-controlled indoor area and an outdoor area.
Extra:
The observation using cameras would not have been distressing and the level of interactions with the toys suggest that their novelty was not in general a source of psychological distress or physical pain. However, one toy was destroyed but it is unknown whether this was a playful act or a reflection of distress.
