Hasset et. al. (monkey toy preference) AICE Psych AS

What are sex differences in toy preference based on?

Nature/nurture debate

Research findings among boys and girls has shown:

•Boys tend to interact with masculine-type toys (e.g. wheeled trucks) as girls tend to favor feminine-type toys (e.g. stuffed animals)

•Boys tend to stick to stereotypical masculine toys as girls will play with a range of masculine & feminine toys

•Studies looking at bio differences among boys & girls point to the notion that girls with CAH (congenital adrenal hyperplasia) producing more androgen favor masculine toys even with stereotypical upbringings

What was the previous monkey study mentioned about?

•Previous study with Vervet monkeys (Alexander & Hines, 2002) looked into sex differences in nonhuman primates with human toys available

•*The study used a single masculine or feminine toy and recorded how long the monkey would play with it

•Contradicting human boy & girl play trends, the male monkeys spent similar time with both masculine & feminine toys, whereas the female monkeys spent more time with the feminine toys

What does Hasset argue with about the previous study?

•Hassett et al. argues that this did not display toy preference itself among nonhuman primates, but rather simply the amount of time playing with a type of toy

•This is the basis for the current study in using Rhesus monkeys is a methodological weakness as the Vervet monkeys were not given a masculine or feminine toy choice

Overall Purpose

•Overall, to investigate potential sex differences among Rhesus monkeys for toy preference

Aims

•To investigate if toy preference is related to biological factors rather than socialization

•To compare the toy preference of male and female Rhesus monkeys to previous research findings for human children

Hypothesis

•Toy preference among sexes is due to biological causes (that influence behavioral and cognitive biases) rather than learned differences

Type of study

Natural Field Experiment

IVs

•(a) sex of monkey (natural IV)

(b) category of toy- wheeled (masculine) or plush (feminine)

(c) rank & age of monkey (natural IV)

DVs

•(a) frequency of playing with toy

(b) duration of playing with toy

(c) magnitude of preference score

Design of the study

•Independent groups

•(a) gender of monkey

•(b) one exposure to each available toy (one truck was repeated)

Sampling Technique

•Opportunity sample from Yerkes National Primate Research Center

•Via Emory University in ATL

Participants

•N= 82… 61 females & 21 males met the criteria for the study

•Sample chosen from a large social group of 135 that have lived there for 25+ years

•14 excluded b/c of participating in other prenatal hormone study & 39 babies excluded as it was too difficult to tell them apart in observations

•Monkeys were pre-coded for social rank & age (used for later data analysis)

•Social rank was previously determined by behavioral observations of grooming, dominance, and submissive behavior

•E.g.- monkey being groomed has higher social status compared to the groomer

Apparatuses

•Available toys were categorized by object properties rather than traditional gender assignments

•The colors and shapes of the items varied

Procedure

•Subjects were housed were their natal (birth) group in a 25m x 25m outdoor compound that had a temperature-controlled interior area also

•Subjects were kept in the enclosed area while researchers placed one wheeled and one plush toy in the outside area, 10m apart

•

•For each trial (7 in total), the placement of the wheeled and plush toy was counterbalanced

•Helps to reduce the possible issue of the monkeys preferring one side of the enclosure and then playing with the toy that is already there

•Each trial was to last 25 minutes (one was only 18 mins as a plush toy was ripped apart)

•For each trial, a video camera was focused on each toy for review by 2 observers

•Each observer noted the identity of each animal (w/age & sex) & the behavior displayed

•The time of interacting with each toy was calculated (giving the 'duration' score)

Behavioral Checklist

•Extended touch

•Hold

•Sit on

•Carry in hand

•Carry in arm

•Carry in mouth

•Drag

•Manipulate part

•Turn entire toy

•Touch (like poke)

•Sniff

•Mouth (put to)

•Destroy

•Jump away from

•Throw

Results:Frequency Data

•FREQUENCY DATA

•Each monkey received their own 'data set' for frequency and duration of behavior(s) with the toys

•Not all individuals interacted with a toy (no data for them)

Those with less then 5 recorded behaviors were not used for data analysis (14 males & 3 females)

•Frequency data showed the following:

Within the sexes:

*Males showed a statistical preference for wheeled toys over plush toys (9.77:2.06)

*Females did not show a statistical preference between the two categories of toys (6.96:7.97)

Comparing the sexes:

Females interacted with the plush toys more, but no statistical difference in preference for wheeled toys

Results: Duration Data

•Within the sexes:

•*Males showed a statistical time spent playing with wheeled toys over plush toys (5mins: 30secs)

•Females did not show a statistical difference among the toys (1 ½ each minutes on average)

•Comparing the sexes:

•*No overall statistical difference was found b/w the sexes for the time spent playing with the wheeled and plush toys

Other Results:

•Magnitude of preference' score was calculated for all Ps (chart below)

•For males= total frequency/total duration w/wheeled toys - total frequency/duration w/plush toys

•For females= opposite (plush-wheeled toys as above)

•Results:

•*Males had a significantly higher preference for wheeled toys whereas females showed no strong preference

•Rank data

•Males did not show a correlation with rank (neither frequency or duration)

•Females showed (a) a positive correlation with rank for frequency of play for wheeled & plush toys and (b) positive correlation with duration only for plush toys

•Age data

•No differences were found

General Results

•Comparison of Rhesus monkeys to human children study (Berenbaum & Hines, 1992)

•Human study looked at 3-8-year-old girls w/CAH compared to boys and found that the girls exposed to higher levels of prenatal androgen preferred 'boy toys' over 'girl toys' (hormonal cause)

•Both Rhesus monkeys and human children showed gender differences

•Males strongly preferred the masculine toys as females slightly preferred the feminine toys

•This preferences was greater among males in both studies

Conclusions

•Hassett et al. note that their findings support a biological basis for differences in toy preference

•In both this study and the Berenbaum & Hines (1992) one, biological hormones influenced the preference for masculine toys

•These hormones "influence behavioral & cognitive biases" which in turn are influenced by learning experiences and social pressures

•Not found in monkeys due to absence of socialization influences (such as mass media)

•Found in humans, such as if boys were to choose to play with 'girl toys,' they would likely receive negative feedback from society than if girls were to choose to play with 'boy toys'

•May explain why boys are much more likely to choose masculine toys whereas girls are more likely to have variation in toy choices

Ethics

•Study was met ethical guidelines while working with animals

•Study conducted in accordance with NIH Guide for the Care & Use of Laboratory Animals

•Took place at the Yerkes National Primate Research Center

•Approved by the Emory University Ethical committee on animal care and use

•Proper housing

•Lived in social/family groups (as in the wild) in large, safe enclosures with access to indoor temperature-controlled areas and outside areas