Interlanguage fossilization is a phenomenon of second language acquisition in which second language learners develop and retain a linguistic system, or interlanguage, that is self-contained and different from both the learner’s first language and the target language. This linguistic system has been variously called interlanguage, approximative system, idiosyncratic dialects, or transitional dialects.
According to Corder  this temporary and changing grammatical system, interlanguage, which is constructed by the learner, approximates the grammatical system of the target language. In the process of second language acquisition, interlanguage continually evolves into an ever-closer approximation of the target language, and ideally should advance gradually until it becomes equivalent, or nearly equivalent, to the target language. However, during the second language learning process, an interlanguage may reach one or more temporary restricting phases when its development appears to be detained;. A permanent cessation of progress toward the target language has been referred to as fossilization. This linguistic phenomenon, interlanguage fossilization, can occur despite all reasonable attempts at learning. Fossilization includes those items, rules, and sub-systems that second language learners tend to retain in their interlanguage, that is, all those aspects of interlanguage that become entrenched and permanent, and that the majority of second language learners can only eliminate with considerable effort. Moreover, it has also been noticed that this occurs particularly in adult second language learners’ interlanguage systems.
Selinker suggests that the most important distinguishing factor related to second language acquisition is the phenomenon of fossilization. However, both his explanation that “fossilizable linguistic phenomena are linguistic items, rules, and subsystems which speakers of a particular native language will tend to keep in their interlanguage relative to a particular target language, no matter what the age of the learner or amount of explanation or instruction he receives in the target language” and his hypotheses on interlanguage fossilization are fascinating in that they contradict our basic understanding of the human capacity to learn. How is it that some learners can overcome interlanguage fossilization, even if they only constitute, according to Selinker, “a mere 5%”, while the majority of second language learners cannot, ‘no matter what the age or amount of explanation or instruction’? Or is it perhaps not that they cannot overcome fossilization, but that they will not? Does complacency set in after second language learners begin to communicate, as far as they are concerned, effectively enough, in the target language, and as a result does motivation to achieve native-like competence diminish?
The concept of fossilization in SLA research is so intrinsically related to interlanguage that  considers it to be a fundamental phenomenon of all SLA and not just to adult learners. Fossilization has received such wide recognition that it has been entered in the Random House Dictionary of the English Language (1987). Selinker’s concept of fossilization is similar to that of  and  all of whom attempted to explore the causes of fossilization in second language learners’ interlanguage.
Fossilization has attracted considerable interest among researchers and has engendered significant differences of opinion. The term, borrowed from the field of paleontology, conjures up an image of dinosaurs being enclosed in residue and becoming a set of hardened remains encased in sediment. The metaphor, as used in SLA literature, is appropriate because it refers to earlier language forms that become encased in a learner’s interlanguage and that, theoretically, cannot be changed by special attention or practice of the target language. Despite debate over the degree of permanence, fossilization is generally accepted as a fact of life in the process of SLA.
Many researchers have attempted to explain this. Workers have attempted to discover: 1) why fossilization occurs  2) the precipitating conditions  3) what kind of linguistic material is likely to be fossilized  and 4) what type of learners are more prone to fossilize. However, there has been almost no investigation by SLA theorists on the possibilities of preventing or overcoming fossilization, and little explanation related to those adult second language learners who overcome one or more ‘areas of stability’ in interlanguage—those learners whose interlanguage does not fossilize, and who reach a high level of proficiency in the second language ).
One factor of obvious relevance is motivation, and studies have been conducted regarding motivation to learning second language, and the relationship of fossilization to the learner’s communicative needs. Arguments have emerged regarding adult learners’ general lack of empathy with target language native speakers and culture. According to, adults do not have the motivation to change their accent and to acquire native-like pronunciation. Unlike children, who are generally more open to target language culture, adults have more rigid language ego boundaries. Thus, adults may be inclined to establishing their pre-existing cultural and ethnic identity, and this they do by maintaining their stereotypical accent. Notwithstanding this, there is a lack of needed research, particularly regarding achievement motivation, especially considering that fossilization can be considered the most distinctive characteristic of adult SLA.
The text of this article is taken with permission from The Role of Achievement Motivation on the Interlanguage Fossilization of Middle-Aged English-as-a-Second-Language Learners by Dr. Zoran Vujisić (2007).
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