Thursday, December 13, 2012

Every Ending is a New Beginning

    Hello again everyone.  This is my last blog post for the Psych 118 class on comparative psychobiology and my topic on foraging and feeding behavior in animals.  It has been a pleasure to research, read and investigate a number of topics from primary literature, review articles, and textbook chapters and blog about them for you.  I hope that the readers have learned something valuable, or have at least found my topics of some interest because I know that I sure have.  Over these past two quarters, blogging has become somewhat of a ritual and a learning experience as I have dived into numerous topics that paralleled our class instruction, as well as those articles that were simply of interest.  I suggest that everyone try some form of free-expression as well, whether it be blogging or keeping a journal about schoolwork, sports, or random topics, I have found it very beneficial and even liberating to express ideas.  By working with a class instructor and mentor, I found it a great learning experience to be able to pick research studies apart, search for important facts and critique with a critical eye.  There is always something to blog about so you should get started too!
     And now on to summarize the most interesting topics and findings that I encountered this quarter.  One of my earliest blog entries came about the black rats of Israel.  This one investigated rats in Israel learning how to strip pine cones to get at the seeds inside.  Rats, on their own, were unable to learn the stripping behavior through simple trial-and-error learning, and the behavior was not passed on genetically.  The researchers came to conclusions about the way rats learn the pine-cone stripping behavior by giving rats partially stripped pine cones and seeing that they were able to get to the seeds inside.  In nature, rats were actually seen stealing partially stripped pine-cones from their mothers and conducting trial-and-error learning, which is a form of instrumental learning, to get to the seeds inside.  There was no insightful learning taking place here, just good ole' trial-and-error learning, with a little bit of help from mom, who had begun stripping the pine-cones, only to have them stolen away.
      This primary research article was followed by the online chapter from Zentall's paper on imitation.  Imitation is defined as any influence that an organism may have on another that results in a similarity of behavior or appearance between the two.  This was an in-depth look at imitation and an analysis of the factors that must be ruled out before a behavior is deemed to be imitation.  One of those factors that must be ruled out is local enhancement or stimulus enhancement.  These terms mean that an observer is drawn to a certain area (local) or a certain individual (stimulus) that is of interest and can eventually lead to some type of behavior experimenting, simply by being in the area.  For example if you see someone messing around with a stack of papers, then your attention will be drawn to that area and, after the person leaves the room, you will also go to see what was so interesting about those papers.  This may lead you to try a bunch of behaviors and shuffle papers around, which could have been confused for imitation, if someone was not careful.  Akins and Zentall performed experiments involving quail which were taught to acquire food by pecking or stepping on a treadle.  The observing quail imitated demonstrators with the same body part that was shown to step or peck in order to receive food.  Although imitative learning is a rather advanced form of learning that is not found in all species, we must not overestimate its importance.  Trial-and-error learning is also a very necessary form of learning that is essential to an exploratory foraging strategy.  When resources are low and animals must go out to find food, imitation will not assist them in finding novel sources of food or novel techniques of uncovering food.  I will get to this idea again with a recap of my last blog article.
       Another topic I talked about was the sponging behavior found among bottle-nose dolphins of East Bay Australia.  This is a behavior whereby dolphins use a sponge on their beak to search the seafloor while foraging for food.  This behavior is transmitted vertically, not horizontally, from mother to offspring, and is rarely found in males.  Strangely, fathers do not teach the behavior to their children, and non-spongers that associate with groups of spongers do not pick up on the behavior either.  It is really a subculture among these dolphins and an exclusive group of dolphins that carries out this interesting technique.  The exact learning mechanism for this sponging behavior has not been researched and identified, but speculations and likely explanations have been made.  Evidence shows that calves spend roughly three to six years with their mothers, during which they forage with their mother and eventually learn the technique that was used.  Dolphins are also well known for observation and imitative abilities, making social learning and imitation a likely explanation for how the behavior came about, rather than independent learning.  If imitation is at play, then it would be an interesting spin-off of the imitation explained by Zentall, as seen in the real world rather than a laboratory.  In any event, the behavior is a unique one in the realm of foraging, and is found solely in this group of dolphins.  These dolphins have actually formed a subculture amongst themselves, whereby they associate with other spongers more than non-spongers.
        One of my favorite topics that I wanted to talk about is that of reward probability and variability in the foraging behavior of rats.  This is the case whereby rats foraging for food will continue to utilize and exploit a source until it is depleted, or they will move on and explore so that they can find a new source.  In this study, rats explored a landmark on a platform that signaled either high or low probability of finding food.  The main result of this study was that rats that encountered a low probability of finding food, tended to explore the area surrounding the landmark, and poke their noses into other food cups, searching for food.  The mean number of nose pokes in the other food cups decreased for rats that encountered a high probability food source.  The reason I enjoyed reading about this study so much is because it not only related to a similar topic we talked about in our Psych 110 class, but also because it makes you think about human experiences in real life.  If we find something that we enjoy, then we will continue to exploit it until it is no longer a reliable source.  At this point, we will explore and conduct trial-and-error until we discover something new that we can latch onto and use.  If we were foraging for food as well, we would go to the source that we have known to be reliable, and continue to search the immediate area surrounding that source until we find what we were looking for.  It is good to see that this is a general foraging strategy that is found in other organisms as well.
      In conclusion, I would like to say that I have been surprised by animal foraging behavior over the past 10 weeks of studying the topic.  This may have been my own fault of underestimating the capabilities of animals, but I genuinely had little knowledge of animals, other than primates, using tools, so it was a pleasant surprise to see dolphins use sponges as tools.  In addition, quail learning pecking or stepping on a treadle shows another dimension of how animals interact with their environment and can actually manipulate their surroundings to achieve a result.  Further similarities between animals and humans continue to surface as research is further extended and conducted in all corners of the world.  One example we learned in class was about how monkeys show successive negative contrast, leading to frustration, when they do not get an expected food reward.  It is a combination of the topics I have been blogging about, as well as those we studied in class that lead me to believe Darwin's theory that the "difference between human intelligence and animal intelligence is a matter of degree, and not of kind".
    It has been a great pleasure and learning experience to blog for the past two quarters.  I hope to continue blogging about school, sports or random topics, now that the forum has been set up and the process is underway.  I hope that everyone has an enjoyable winter break and continues to check in for updates on my blog!

Wednesday, December 5, 2012

Reward Probability and the Variability of Foraging Behavior in Rats

    This week's blog post is about a topic and paper from my very own professor, Dr. Aaron Blaisdell and his colleague at the University of California, Los Angeles, Dr. Stahlman.  The primary research study is called "Reward Probability and the Variability of Foraging Behavior in Rats" and can be found in the International Journal of Comparative Psychology from 2011. 
     The main purpose of this study was to build upon the idea of exploitation vs. exploration for food foraging behavior in rats.  Research has previously been conducted in this area involving nose-poking, bar-pressing and bar-sequence variability in rats.  When a source is continuously providing reinforcement and reward, then we will continue to go to that source and exploit it until something changes.  The change may come about with a reduced probability of reward as resources dwindle in nature, leading to more variability in the form of responding.  This is the typical procedure that occurs when a behavior is being extinguished in a lab.  Reward will no longer be as available as was previously learned (the probability of reward is reduced), until the participants change their behavior and a new response could be conditioned.  In nature, this is seen as well, as food or resources can be exploited and used up, until very little remains at the source.  This would require animals to begin searching for new areas of food, and change their typical behavior so that they can explore their surroundings.  The behavior of variability and exploration increases the probability that an organism is going to discover and exploit more highly rewarded behaviors.
      In this experiment, rats were investigated for their behavioral variability when the probability of food reward was alternated between 100% and 20% in an open field.  10 female rats were used in this experiment and were placed in plastic tubes in a vivarium (an enclosure meant to keep animals).  The open field apparatus was made up of a flat piece of wood placed 94cm above the floor with sixteen cups in a 4x4 arrangement arranged so that their top extended only 2cm above the surface of the open field.  The cups were then filled with wood shavings and possibly a positive reinforcement - Cocoa Puffs - above or below the wood shavings.
      The procedure consisted of habituation training sessions, followed by training and testing sessions.  For two habituation sessions, cereal was scattered across the open field and rats were allowed to explore for ten minutes.  I presume that this was done so that rats become familiar with the idea of searching for food and the apparatus, and so that they would not be surprised about the sources of food during any training or testing sessions.  This was followed by eight training sessions, each session consisting of two HI trials and two LO trials.  The design consisted of wooden landmarks(LM) with a separate LM for the HI and LO trials.  The landmarks were meant to point rats in the direction of food and signal the probability of food.  The trials ended when all the food had been consumed or after 3 minutes.  The testing session followed this and consisted of LO trials with only 20% probability of finding food and HI trials that remained at 100%.  Trials were terminated when rats searched the goal cup or after 3 minutes.  The interresponse distance was measured, which served as a measure of spatial variability in responding.  In addition, the number of mean searches was measured.
         The results showed that there was no significant effect of mean searchers on HI vs LO trials, but there was a trend toward more searchers on LO trials (2.8 vs 2.1).  Results also showed that over the entire testing session, the mean number of searches decreased over time, leading to decreased variability for both the HI and LO trials.  The distribution of search frequencies was wider with LO than HI trials, showing that behavioral variability was greater with a reduced expectation of reward.  Finally, the last important finding from the study was that out of 184 trials, rats failed to find the cup with the food in it (goal cup) only 1% of the time in the HI trials and 7% of the time in the LO trials.
         The significance and application of this research cannot be overstated.  This research is consistent with other findings and also expands upon previous research with lever-pressing in rats or screen-pecking in pigeons with a more environmentally applicable demonstration.  Animals in the wild will utilize the techniques that were demonstrated in this experiment because it is essential to their survival  These findings support the behavior systems view of foraging behavior showing that animals may engage in less consummatory mode behaviors and more in appetitive (search) mode behaviors when the expectation of reward is low.  If one source isn't leading to results, then animals will conduct trial-and-error and vary their responses until something works.  When the expectation of reward is high, then animals will continue to exploit a source until it is depleted.  This is a naturally adaptive trait, and now it has been proven to occur in an open field study with food reinforcement.
          As the researchers allude to, further research conducted in this field would include discovering the role of variability and how it leads to actions that are highly-rewarded and what the process is in that.  In addition, I would like to see experimenters look at how much effort would animals be willing to input in exploiting resources.  For example, let's say animals have a steady source of food that provides a 70% reward, but there is a nearby food source that provides 90%, however, it would require extra effort/energy to get to or to unlock and begin exploiting.  Are animals always comfortable in the source that they are currently exploiting until it is depleted, or are they always looking for the highest probability reward system?


Stahlman, W. David, and Aaron P. Blaisdell.  "Reward Probability and the Variability of Foraging   
           Behavior in Rats."  International Journal of Comparative Psychology 24 (2011): 168-176.