This paper is being submitted to Dr. Willner on 12/08/11 in partial fulfillment of the requirements for Psychology 434 Research in Learning. The Effect of Uncertainty on Social Food Preferences in Long-Evans Rats
The present study investigates the effects of uncertain environments on social food preferences among male Long-Evans rats. Exposure to an uncertain environment that potentially creates anxiety can be a factor that plays a role in when a rat is affected by social learning. Previous studies have focused mainly on the phenomenon of social transmission of food preference. However, there have been few studies focusing mainly on the uncertainty effects of a novelty environment correlating with social transmission of food preferences. The present study will examine the effects of uncertainty on social learning in rats. Social learning is a theory that suggests that animals will copy another’s behavior if it is available for them to do so. Laland (2004) believes that some animals engage in social learning because it is an easy and beneficial way to help find valuable information such as: nutrition, water, escaping predators, and learning the environment around them. There have been relatively few attempts to test theories of learning, however Laland (2004) makes an attempt to suggest these theories. Laland (2004) came up with separate categories, “when” and “who”.
The “when” category is aimed to predict theories of when animals might increase their reliance on social learning, and the “who” category is aimed to predict which animals behaviors provide the most useful information (Laland, 2004). The theory of uncertainty, as found by Laland (2004), is a part of the “when” strategies that species engage in. This theory recognizes that some animals engage in copying when uncertain if they are unclear of the nature of an environment and solely need to rely on social learning (Laland, 2004). Galef (2009) aimed to test the suggestions that Laland (2004) made about social learning by using the “who” and “when” strategies. Galef tested these suggestions by using what is known as the social transmission of food preference. Galef & Wigmore (1983) tested the phenomenon of social
transmission of food preference by giving a naïve observer rat two novel diets after interacting with a demonstrator rat that had been exposed to one of those two diets. Galef & Wigmore (1983) found that an observer rat preferred to eat the diet that the demonstrator, which they had previously interacted with, consumed.
A study conducted a year later tested more than just social transmission of food preference. This study was determined to see if other factors effected social transmission of food preference such as: unfamiliar versus familiar demonstrator rats, different ages of rats, domesticated versus wild rats, and food deprived versus non-food deprived rats (Galef, Kennett & Wigmore, 1984). Galef et al. (1984) conducted their study and the data indicated that the idea of social transmission of food preference is a robust phenomenon. Galef (2009) points out that social learning is common, however it may not always be for the better as opposed to individual learning. He suggests that individual learning might be more beneficial than social learning in the long run because social information changes over time in some environments. Galef (2009) also states that individual learning is more expensive and accurate than social learning. Galef (2009) stated that social learning is possibly genetic. It is evident that learning has to begin by being asocial and then become social or else we would be running in circles. Galef (2009) believes that individual learning is better for long-term benefits.
The present study will be focusing more on social learning than asocial learning. Animals are most likely to engage in social learning when the environment is highly variable and when it is uncertain (Laland, 2004; Galef, Dudley, & Whiskin, 2008; Galef, 2009). Laland (2004) suggests that animals may exploit in a “copy when uncertain” behavior when the environment is generally unclear. Galef (2009) also found that social learning is relied upon when a rat is uncertain. For the most part, animals engaging in social learning can be confirmed (Laland, 2004; Galef, Dudley, & Whiskin, 2008; Galef, 2009). Environmental stability was tested on Norway rats on social learning of food preferences (Galef & Whiskin, 2004). These results showed an increase in preference for the demonstrator’s diet in both environmentally stable conditions and in the variable-environment groups. This was another study that confirmed the belief that rats prefer a demonstrated diet when they are uncertain. All of the previous studies provide information to show that it is evident that animals learn under uncertain conditions and it has an effect on social transmission of food preference (Laland, 2004; Galef, Dudley, & Whiskin, 2008; Galef, 2009; Galef & Whiskin, 2004).
On the basis of the studies reviewed above, the primary purpose of the present study was to test whether the rats would show an increase in social food preference after exploring an uncertain environment. The amount of flavored food consumed by observers will determine their preference. It is anticipated that observer rats that explore the open field prior to their interaction with the demonstrator rat will show an increased preference for the demonstrated diet as opposed to the observer rats that are only handled prior to the interaction. The hypothesis of the present study is that if uncertainty is present, social food preference will increase. Method
Twenty-nine naïve, adult male Long-Evans rats from the university vivarium were used as demonstrators and observers. Fifteen pairs of rats were used, while one demonstrator was used twice. The rats ranged in weight from 500 to 800 g. Rats used as demonstrators and observers were food deprived, except when having free access to plain ground food for 60 minutes per day for the two days prior to the training trial. All rats were randomly assigned to demonstrators or observers. The subjects were housed in individual stainless steel cages with free access to water while on food deprivation. Apparatus and Materials
The subjects were individually housed in stainless steel and wire mesh cages that were 25cm x 18cm x 18cm. All rats were first trained to eat plain, ground rat chow in their home cages for one hour per day for the two pre-training days. For these two pre-training days, food was presented in a ceramic cup, which was 8cm in diameter and 4cm high. The ceramic cup was placed on top of a ceramic tile, which was 8cm x 15cm, to help count for spillage. On the third day, the demonstrator rats were placed in a smaller compartment of a red Plexiglas apparatus (90cm x 35cm x 30cm) divided by a piece of mesh into two compartments of unequal size (60cm x 30cm, 30cm x 30cm). The group of demonstrator rats (n=15) was fed high fat ground rat chow for one hour that had either ground cinnamon (1% w/v) or ground cocoa (2% w/v) added to it.
To manage uncertainty, one group of observer rats (n=8) was placed into a 60cm x 60cm x 40cm wooden open field environment prior to their interaction with the demonstrator rats. The other group of observer rats (n=7) was handled, but remained in their home cage until placement into the test apparatus for their interactions with the demonstrator rats. For the training day, food was placed in the same ceramic cups as used in the pre-training days. However, they were connected to the floor of the apparatus instead of on a small tile. High fat food known as Harlan Teklad Rodent Breeder Diet (#7004) was used for the pre-training and training days. Procedure
After two days of pre-training with a feeding regime of one hour of access to food per day, the preference test took place. Observer rats were either in the experimental condition, where they were placed into the open field prior to interaction with the demonstrator rat, or the control condition where they were handled shortly before their interaction with the demonstrator. In the social transmission of food preference task, observer rats are exposed to a distinctive food from the breath of a demonstrator rat. To determine the preference of the observer rat, they were given simultaneous access to the demonstrated food as well as another equally palatable food for a period of time. On the third day, the training day, the group of demonstrator rats was placed in the smaller compartment of the apparatus and fed one of the two diets, cinnamon or cocoa, for one hour.
Cinnamon and cocoa diets were randomly counterbalanced across rats in the two uncertainty conditions. Approximately half of the observer rats were exposed to demonstrators who had previously eaten a cinnamon diet, and the other half were exposed to a demonstrator rat that had eaten a cocoa diet. After forty-five minutes of the demonstrator rat feeding, an observer rat was either placed into an open field or handled for fifteen minutes. The observer rat was then placed into the larger of the two compartments of the apparatus to interact with the demonstrator rat for fifteen minutes. After that fifteen-minute period was up, the demonstrator was returned to his home cage and the observer rat was given a one-hour period with simultaneous access to cinnamon and cocoa flavored diets. At the end of the one-hour period, the observer rat was placed back in his home cage and the amount of each diet consumed was measured. The preference for the demonstrated food will be determined by calculating a percent of its total intake of food during the preference test.
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