PSY2061 Monash Role of Effort and Impulsivity in Reversal Learning Questions

Brief introduction
One of the main characteristics of human behaviour is its flexibility. We must be able to detect regularpatterns in our environment, and also be sensitive to disruptions to those regularities, so that we canadapt our behaviour accordingly. Imagine that the bus you have been catching to work every morningfor the last few years has been late for the last three days. The decision that you must make iswhether this represents merely a temporary disruption of otherwise regular scheduling (say, due toroad-works), or whether the bus timetable has changed altogether (such that it is no longer stoppingat the previously scheduled time). In other words, you must detect whether this irregularity representsa temporary change in an otherwise stable environment, or whether it represents a fundamentalchange in the environment altogether.
Individuals differ significantly in how fast they learn or adapt to these sorts of situations. The way inwhich decisions such as this are resolved by the brain has been studied with a paradigm known as”˜probabilistic reversal learning.’ Each of these terms refer to key aspects of the paradigm:
Individuals are required to learn about the relative value of stimuli presented before them(e.g., which bus you prefer to catch)
The values of these stimuli periodically reverse (i.e., the bus timetable changes).
The values of the stimuli vary probabilistically (i.e., even the bus you usually prefer to catchmay sometimes be late, but on average is better than the other alternative).
Using this paradigm, we now have significant insights into the neural circuitry and computationalmechanisms which mediate adaptive human behaviour. Flexible learning is mediated by a neuralnetwork comprising the prefrontal cortex and basal ganglia (Clark et al., 2004; Cools et al., 2002;Izquierdo et al., 2017, Peterson et al., 2009), and dopamine is a key neurotransmitter in this processof reversal learning. Importantly, a separate literature has revealed that dopamine is important, notonly in learning, but is also critical for motivating individuals to exert effortful actions (Chong et al.,2015). Given the dual role of dopamine in motivating effortful actions, and in probabilistic reversallearning, this study will explore the relationship between effort exertion and learning. Specifically, weask:
How probabilistic reversal learning can differ based on the amount of force that individualsmust exert to register their responses.
How personality differences (e.g., in impulsivity) are related to learning.
You may have been a participant in this study, but, when writing your report, it is important that youwrite from the perspective of the researcher.
Design
This experiment involved two phases. In an initial phase, the maximum voluntary contraction (MVC)for each participant was determined by squeezing each force dynamometer as hard as possible.Participants then undertook the learning task. Participants were presented with two abstract shapes,with one of these stimuli being more valuable on average than the other. The more valuable stimuluswas rewarded 70% of the time, and the less valuable stimulus was rewarded 30% of the time. Arewarded stimulus was associated with a gain of one point, and an unrewarded stimulus wasassociated with no gain. The primary task was to learn which of the two stimuli was more valuable onevery trial, and to accrue as many points as possible. Importantly, the relative value of the stimuliperiodically reversed, such that the more valuable stimulus would then be worth less, and vice versa.Participants were instructed to detect when that change occurred, and switch their preferencesaccordingly. Stimuli were presented randomly to the left or right of fixation, and participants registeredtheir preferences by squeezing the corresponding (left or right) dynamometer. Participants performedtwo blocks: one in which only a small force needed to be applied (5% of MVC), and the other in whicha harder force was required to make a choice (30% MVC). The order of blocks was counterbalancedacross participants.
Built into this design was a further experimental manipulation to examine whether the time at whichparticipants exert a low or high force influenced learning on this task. Participants were divided intothree groups (“˜A’, “˜B’, and “˜C’). Participants in one group (“˜A’) were only required to provide a singlesqueeze (with a high or low force) to register their choice and simultaneously receive feedback. Incontrast, participants in Groups B and C were required to provide two squeezes. Those in Group B
exerted a high or low force to register their choice, and a low force to reveal the outcome. Those inGroup C undertook the reverse manipulation, by always exerting low force to register their choice, buteither a low or high force to reveal the outcome. For the purposes of this lab report