like the nudge theory, and relative forces like the Adams' equity theory. History The psychological contract came to be identified in 1960 by Argyris. However, only within the last ten to fifteen years has it become more popular and more research been done on the subject. As studies in industrial relations developed and grew more complex, it was revealed that employees are more likely to perform better in certain work environments. The early works of Frederick Winslow Taylor focused on how to enhance worker efficiency. Building upon this, Douglas McGregor developed Theory X and Theory Y to define two contrasting types of management styles that were each effective in attaining a certain goal. These differing management types hold different psychological contracts between employer and employee, as described in more detail under "formation of the psychological contract." Works by Denise M. Rousseau and later went more in-depth on the details and perspectives of the psychological contract. Sandra L. Robinson indicated employees commonly reported a breach of the psychological contract within several years of beginning their position, and that the effects of contract breach negatively effected employee productivity and retention. Maslach, Schaufeli and Leiter stated in 2001: "Now employees are expected to give more in terms of time, effort, skills, and flexibility, whereas they receive less in terms of career opportunities, lifetime employment, job security, and so on. Violation of the psychological contract is likely to produce burnout because it erodes the notion of reciprocity, which is crucial in maintaining well-being." The formation of the contract Psychological contract formation is a process whereby the employer and the employee or prospective employee develop and refine their mental maps of one another. According to the outline of phases of psychological contract formation, the contracting process begins before the employment itself, and develops throughout the course of employment. As the employment relationship grows, the psychological contract also grows and is reinforced over time. However, the psychological contract is effective only if it is consented to on a voluntary basis. It is also useful in revealing what incentives workers may expect to receive in return for their employment. There are two types of contracts depending on the nature of the relationship between employee and employer. These are relational psychological contracts and transactional psychological contracts. Transactional psychological contract: focuses more on the explicit elements of the contract without accounting much for the intrinsic motivations of workers. These