Peer mentoring: A move towards addressing inequality between PhD students

The number of students enrolling in postgraduate by research degrees has seen a large increase in recent years, a trend which is evident globally as well as within Australia. However, the rate at which PhD students are dropping out has also increased, indicating that students are not receiving adequate resources to support them throughout their candidature. We highlight that mentoring programs are effective in addressing inequality between PhD students, and describe a program that we have recently launched at UNSW Sydney

Behavioral correlates of the decision process in a dynamic environment: post-choice latencies reflect relative value and choice evaluation

One characteristic of natural environments is that outcomes vary across time. Animals need to adapt to these environmental changes and adjust their choices accordingly. In this experiment, we investigated the sensitivity with which rats could detect, and adapt to, multiple changes in the environment. Rats chose between two spouts which delivered 5% sucrose rewards with distinct probabilities. Across three phases, reward probabilities changed in size (large or small) and direction (increase or decrease). A discrete trial-structure was used, which allowed the choice process to be decomposed into three distinct response latency measures (choice execution latency, spout sampling duration, and trial-initiation latency). We found that a large decrease in reward probabilities rapidly produced the greatest change in choice proportions. The time taken to execute a choice reflected the differences in reward probabilities across the two spouts in some cases, but also reflected training history. By contrast, the amount of time rats spent responding at reward spouts in anticipation of reward consistently reflected the relative likelihood of reward across the two spouts and not the absolute probability of reward. The latency to initiate the subsequent trial reflected choice evaluation. These three response latencies thus indexed key behavioral correlates of the choice process as it unfolds in time. We discuss how this paradigm can be used to assess the corresponding neural correlates of decision-makin

Dynamics of pre- and post-choice behaviour: rats approximate optimal strategy in a discrete-trial decision task

We simulate two types of environments to investigate how closely rats approximate optimal foraging. Rats initiated a trial where they chose between two spouts for sucrose, which was delivered at distinct probabilities. The discrete trial procedure used allowed us to observe the relationship between choice proportions, response latencies and obtained rewards. Our results show that rats approximate the optimal strategy across a range of environments that differ in the average probability of reward as well as the dynamics of the depletion-renewal cycle. We found that the constituent components of a single choice differentially reflect environmental contingencies. Post-choice behaviour, measured as the duration of time rats spent licking at the spouts on unrewarded trials, was the most sensitive index of environmental variables, adjusting most rapidly to changes in the environment. These findings have implications for the role of confidence in choice outcomes for guiding future choices.This work was supported by the Australian National Health & Medical Research Council Project grant no. 1028670

Temporal dynamics of choice behaviour: an examination of pre- and post-choice latencies in rats and humans

Animals and humans face choices every day. Survival depends on whether the choices we make are adaptive and reflect the demands of the environment. One feature of the choice environment is that the outcomes associated with our choices are stochastic (probabilistic). Two other features are that choice outcomes are not directly indicated but must be learnt through experience, and that choice outcomes can vary over time. The process of choice thus consists of various stages within which complex features of the environment are integrated to guide choice. Previous research has mainly focused on how animals and humans allocate their choices. However, choice allocation does not capture the entire choice process. This thesis investigates choice behaviour beyond choice allocation by assessing pre- and post-choice latencies when animals and human choose between two probabilistically rewarded options. The experiments presented here used a discrete-trial procedure which allowed the choice process to be decomposed into three distinct behavioural stages. We investigated rat choice behaviour in Chapters 2 and 3, where we analysed response latencies within these three distinct choice stages and investigated how they related to changes in choice allocation. In Chapter 4, we sought to identify the differences and similarities in choice behaviour between rats and humans.In Chapter 2, we simulated two types of environments to investigate how closely rats approximated optimal foraging. We found that rats approximated the optimal strategy across the two environments that differed in the average probability of reward as well as the dynamics of the depletion-renewal cycle. In Chapter 3, we presented rats with reward probabilities that were dynamic across three phases: reward probabilities changed in size (large or small) and direction (increase or decrease). We found that a large decrease in reward probabilities rapidly produced the greatest change in choice proportions. In Chapter 4, we compared choice behaviour between rats and humans under two paradigms. Firstly, we used a cued choice paradigm where subjects were presented with a cue that directed them as to which of two options to respond for rewards. Secondly, subjects were presented with an un-cued task, where they were free to choose between two options in order to procure rewards. An interesting difference between rats and humans was observed: choice behaviour for humans, but not rats, was sensitive to free-choice aspects of the tasks.In this thesis, choice was examined across a variety of environments, and across rats and humans. Throughout all the experiments reported here, the analysis of behavioural latencies provided information about environmental contingencies which were not available from an analysis of choice allocation alone. This thesis thus demonstrates novel methods for assessing choice behaviour with the potential to also elucidate the underlying neural mechanisms

Temporal dynamics of choice behavior in rats and humans: an examination of pre- and post-choice latencies

Identifying similarities and differences in choice behavior across species is informative about how basic mechanisms give rise to more complex processes. In the present study, we compared pre- and post-choice latencies between rats and humans under two paradigms. In Experiment 1, we used a cued choice paradigm where subjects were presented with a cue that directed them as to which of two options to respond for rewards. In Experiment 2, subjects were free to choose between two options in order to procure rewards. In both Experiments rewards were delivered with distinct probabilities. The trial structure used in these experiments allowed the choice process to be decomposed into pre- and post-choice processes. Overall, post-choice latencies reflected the difference in reward probability between the two options, where latencies for the option with higher probability of reward were longer than those for the option with lower probability of reward. An interesting difference between rats and humans was observed: the choice behavior for humans, but not rats, was sensitive to the free-choice aspect of the tasks, such that in free-choice trials post-choice latencies no longer reflected the difference in reward probabilities between the two options

Rats quit nicotine for a sweet reward following an extensive history of nicotine use

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Data from: Dynamics of pre-choice and post-choice behaviour: rats approximate optimal strategy in a discrete-trial decision task

Data from: Dynamics of pre-choice and post-choice behaviour: rats approximate optimal strategy in a discrete-trial decision tas

The Effect of Early List Manipulations On the DRM Illusion

The Deese–Roediger–McDermott (DRM) paradigm is widely used to study false memory in the laboratory. It tests memory for lists of semantically related words (correct list item memories) and their non-presented associates (false lure memories). Evidence suggests that early items in DRM lists could make an especially significant contribution to false memories of lures, as they may critically influence the underlying associative activation and/or gist extraction processes. The present study tested this suggestion by using two manipulations that were intended to affect processing of early DRM list items. The first was interpolation of a semantically unrelated distractor item among the list items (Experiments 1 and 2). The second was arranging for these items to be either the strongest or weakest associates of the lure (Experiment 2). In Experiment 1, a distractor item reduced both list item and lure recall when presented early in a DRM list, but selectively disrupted list item recall when presented late in the list. In Experiment 2, arranging for the early list items to be the weakest associates of the lure reduced false recall of the lure but had no effect on list item recall. The findings are discussed with respect to theories that explain false memory in the DRM protocol, including fuzzy trace theory (FTT) and activation–monitoring theory (AMT). They are also discussed with respect to general theories of memory and the potential role of category/context information in generating false memories