scholarly journals The Importance of Trials

2019 ◽  
Author(s):  
Justin Harris

Many theories of conditioning describe learning as a process by which stored information about the relationship between a conditioned stimulus (CS) and unconditioned stimulus (US) is progressively updated upon each occasion (trial) that the CS occurs with, or without, the US. These simple trial-based descriptions can provide a powerful and efficient means of extracting information about the correlation between two events, but they fail to explain how animals learn about the timing of events. This failure has motivated models of conditioning in which animals learn continuously, either by explicitly representing temporal intervals between events, or by sequentially updating an array of associations between temporally distributed elements of the CS and US. Here, I review evidence that some aspects of conditioning are not the consequence of a continuous learning process but reflect a trial-based process. In particular, the way that animals learn about the absence of a predicted US during extinction suggests that they encode and remember trials as single complete episodes rather than as a continuous experience of unfulfilled expectation of the US. These memories allow the animal to recognise repeated instances of non-reinforcement and encode these as a sequence which, in the case of a partial reinforcement schedule, can become associated with the US. The animal is thus able to remember details about the pattern of a CS’s reinforcement history, information that affects how long the animal continues to respond to the CS when all reinforcement ceases.

2020 ◽  
Author(s):  
C. K. Jonas Chan ◽  
Justin Harris

Pavlovian conditioning is sensitive to the temporal relationship between conditioned stimulus (CS) and unconditioned stimulus (US). This has motivated models that describe learning as a process that continuously updates associative strength during the trial or specifically encodes the CS-US interval. These models predict that extinction of responding is also continuous, such that response loss is proportional to the cumulative duration of exposure to the CS without the US. We review evidence showing that this prediction is incorrect, and that extinction is trial-based rather than time-based. We also present two experiments that test the importance of trials versus time on the Partial Reinforcement Extinction Effect (PREE), in which responding extinguishes more slowly for a CS that was inconsistently reinforced with the US than for a consistently reinforced one. We show that increasing the number of extinction trials of the partially reinforced CS, relative to the consistently reinforced CS, overcomes the PREE. However, increasing the duration of extinction trials by the same amount does not overcome the PREE. We conclude that animals learn about the likelihood of the US per trial during conditioning, and learn trial-by-trial about the absence of the US during extinction. Moreover, what they learn about the likelihood of the US during conditioning affects how sensitive they are to the absence of the US during extinction.


Author(s):  
Steven Hurst

The United States, Iran and the Bomb provides the first comprehensive analysis of the US-Iranian nuclear relationship from its origins through to the signing of the Joint Comprehensive Plan of Action (JCPOA) in 2015. Starting with the Nixon administration in the 1970s, it analyses the policies of successive US administrations toward the Iranian nuclear programme. Emphasizing the centrality of domestic politics to decision-making on both sides, it offers both an explanation of the evolution of the relationship and a critique of successive US administrations' efforts to halt the Iranian nuclear programme, with neither coercive measures nor inducements effectively applied. The book further argues that factional politics inside Iran played a crucial role in Iranian nuclear decision-making and that American policy tended to reinforce the position of Iranian hardliners and undermine that of those who were prepared to compromise on the nuclear issue. In the final chapter it demonstrates how President Obama's alterations to American strategy, accompanied by shifts in Iranian domestic politics, finally brought about the signing of the JCPOA in 2015.


Author(s):  
Terence Young ◽  
Alan MacEachern ◽  
Lary Dilsaver

This essay explores the evolving international relationship of the two national park agencies that in 1968 began to offer joint training classes for protected-area managers from around the world. Within the British settler societies that dominated nineteenth century park-making, the United States’ National Park Service (NPS) and Canada’s National Parks Branch were the most closely linked and most frequently cooperative. Contrary to campfire myths and nationalist narratives, however, the relationship was not a one-way flow of information and motivation from the US to Canada. Indeed, the latter boasted a park bureaucracy before the NPS was established. The relationship of the two nations’ park leaders in the half century leading up to 1968 demonstrates the complexity of defining the influences on park management and its diffusion from one country to another.


2012 ◽  
Vol 39 (1) ◽  
pp. 1-51 ◽  
Author(s):  
Robert J. Kirsch

ABSTRACT Utilizing archival materials as well as personal interviews and correspondence with personnel of the Financial Accounting Standards Board (FASB) and International Accounting Standards Committee/Board (IASC/B), including former Board chairmen and staff members, this paper examines the development of the working relationships between the FASB and the IASC/B from their earliest interactions in 1973 through the transformation of the IASC into the IASB and the Convergence Program rooted in the 2002 Norwalk Agreement up to 2008.


Author(s):  
Frédéric Grare

India’s relationship with the United States remains crucial to its own objectives, but is also ambiguous. The asymmetry of power between the two countries is such that the relationship, if potentially useful, is not necessary for the United States while potentially risky for India. Moreover, the shift of the political centre of gravity of Asia — resulting from the growing rivalry between China and the US — is eroding the foundations of India’s policy in Asia, while prospects for greater economic interaction is limited by India’s slow pace of reforms. The future of India-US relations lies in their capacity to evolve a new quid pro quo in which the US will formulate its expectations in more realistic terms while India would assume a larger share of the burden of Asia’ security.


Author(s):  
David Willetts

Universities have a crucial role in the modern world. In England, entrance to universities is by nation-wide competition which means English universities have an exceptional influence on schools--a striking theme of the book. This important book first investigates the university as an institution and then tracks the individual on their journey to and through university. In A University Education, David Willetts presents a compelling case for the ongoing importance of the university, both as one of the great institutions of modern society and as a transformational experience for the individual. The book also makes illuminating comparisons with higher education in other countries, especially the US and Germany. Drawing on his experience as UK Minister for Universities and Science from 2010 to 2014, the author offers a powerful account of the value of higher education and the case for more expansion. He covers controversial issues in which he was involved from access for disadvantaged students to the introduction of L9,000 fees. The final section addresses some of the big questions for the future, such as the the relationship between universities and business, especially in promoting innovation.. He argues that the two great contemporary trends of globalisation and technological innovation will both change the university significantly. This is an authoritative account of English universities setting them for the first time in their new legal and regulatory framework.


This volume addresses the relationship between archaeologists and the dead, through the many dimensions of their relationships: in the field (through practical and legal issues), in the lab (through their analysis and interpretation), and in their written, visual and exhibitionary practice--disseminated to a variety of academic and public audiences. Written from a variety of perspectives, its authors address the experience, effect, ethical considerations, and cultural politics of working with mortuary archaeology. Whilst some papers reflect institutional or organizational approaches, others are more personal in their view: creating exciting and frank insights into contemporary issues that have hitherto often remained "unspoken" among the discipline. Reframing funerary archaeologists as "death-workers" of a kind, the contributors reflect on their own experience to provide both guidance and inspiration to future practitioners, arguing strongly that we have a central role to play in engaging the public with themes of mortality and commemoration, through the lens of the past. Spurred by the recent debates in the UK, papers from Scandinavia, Austria, Italy, the US, and the mid-Atlantic, frame these issues within a much wider international context that highlights the importance of cultural and historical context in which this work takes place.


Author(s):  
Dennis C. Spies

The chapter summarizes the New Progressive Dilemma (NPD) debate, identifying three arguments from comparative welfare state and party research likely to be relevant to the relationship between immigration and welfare state retrenchment: public opinion, welfare institutions, and political parties. Alignment of anti-immigrant sentiments and welfare support varies considerably between countries, especially between the US and Europe, leading to different party incentives vis-à-vis welfare state retrenchment. The chapter introduces insights from comparative welfare state and party research to the debate, discussing inter alia, political parties in terms of welfare retrenchment, immigrants as a voter group, and cross-national variation of existing welfare institutions. It addresses the complex debates around attitudinal change caused by immigration, levels of welfare support, voting behavior, and social expenditures. Combining these strands of literature, a common theoretical framework is developed that is subsequently applied to both the US and Western European context.


Author(s):  
J. R. McNeill

This chapter discusses the emergence of environmental history, which developed in the context of the environmental concerns that began in the 1960s with worries about local industrial pollution, but which has since evolved into a full-scale global crisis of climate change. Environmental history is ‘the history of the relationship between human societies and the rest of nature’. It includes three chief areas of inquiry: the study of material environmental history, political and policy-related environmental history, and a form of environmental history which concerns what humans have thought, believed, written, and more rarely, painted, sculpted, sung, or danced that deals with the relationship between society and nature. Since 1980, environmental history has come to flourish in many corners of the world, and scholars everywhere have found models, approaches, and perspectives rather different from those developed for the US context.


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