Lexical bundles in textbooks
Multi-word units and metaphor in ESP
Lexical bundles in textbooks have been the subject of further research to find out more about the frequency and function of bundles in texts which EAP/ESP students read in their university studies. These studies have extended the fields of lexical bundles research. Chen and Baker (2010) found 105 four-word bundles in a corpus of Electrical Engineering textbooks, and classified them into the functional categories from Biber et al. (2004). The largest group of bundles in the corpus were referential bundles (78%), followed by stance bundles (19%), and discourse bundles (3%) (Chen & Baker, 2010). Comparing those bundles with those found in a corpus of Electrical Engineering materials for ESP, Chen and Baker (2010) found that the learning materials had different proportions of lexical bundles in the three categories although the frequency order was the same as in the textbook corpus: referential bundles (88%), stance bundles (9%) and discourse organisers (3%).
In a study of first-year Business and Engineering university textbooks and of intermediate and advanced EAP textbooks, Wood and Appel (2014) analysed three to five word formulaic sequences (which they term multi-word constructions). They looked at the boundary between three and four-word constructions; that is, using the multi-word unit at the end of the as an example, this five word sequence contains a range of possible sequences, including at the end, the end of, at the end of and the end of the. Wood and Appel (2014) approached this challenge in two ways, using their corpora of first-year university Business textbooks (774,042 words) and Engineering textbooks (804,071 words) to compare with five EAP textbooks. First, they identified root structures, by examining the frequency of three word constructions within four-word constructions. That is, they looked at whether the three word construction as long as was more or less frequent than the four-word construction as long as the. By doing this, they could then list the root three word structure and reduce the number of constructions which ended with a or the. For example, the amount of occurs 375 times in their Engineering and Business corpus, compared to the amount of the which occurred 45 times. In this example, Wood and Appel (2014) list the construction like this: the amount of (the) to indicate that the amount of is the root structure and that the in brackets is a variable option. The second step was to consider overlaps between four-word sequences, again to identify root structures. This step meant that at the end of and the end of the combined to be listed as (at) the end of (the). Wood and Appel (2014) found that the multi-word constructions were often not included in the EAP textbooks in their study and that these sequences tended not to be the focus of pedagogy in the textbooks.
Some studies have investigated lexical bundles in specific disciplines, such as Grabowski’s (2015) research on Pharmaceutical lexical bundles in English textbooks and three other non-academic text types in the discipline. The detailed comparison of lexical bundles showed examples related to administering medicine, and processes and procedures related to medicine (for example, metabolised in the liver and approved for treatment) (Grabowski, 2015). Such studies as Chen and Baker (2010), Wood and Appel (2014) and Grabowski (2015) are useful because they investigate functions and boundaries of lexical bundles in learning materials. This research can inform decisions by textbook writers, learners and teachers on the lexical bundles which are worth focusing on and where materials might need to be adapted to be more like textbooks which students will read in their university studies.