Studies investigating the potential role of first language (L1) transfer, particularly those examining Universal Grammar (UG) features, have identified potential problems when focusing on acquisition of morphology at the syntactic-semantic level. This focus is considered one point of difficulty in acquiring second language (L2) features, whether learning new features or cross-linguistically reassembling different features, as suggested in Lardiere’s (2009a) Feature Reassembly Hypothesis (FRH). The FRH is used as the basis for this study, focusing on Saudi Arabic learners’ acquisition of the English present perfect compared with their acquisition of the past simple, in which features for tense and aspect overlap but also differ between the two languages. Some linguists argue that relevant features of the present perfect are mainly related to grammatical aspect, which I assert is not taught in standard textbooks in this context. This study investigates whether acquiring the features of the English present perfect, compared with the past simple, are problematic for Saudi Arabic L1 classroom learners, and whether a targeted, linguistically informed, input-rich teaching intervention can lead to improvement. Following an initial preliminary study, the main research design followed a quasi- experimental approach, with 41 Saudi Arabic classroom learners divided into an experimental group (n = 29) and a control group (n = 12). The experimental group received focus on form (FoF) instruction in a communicative environment, with reinforced texts, over the course of six weeks. Two instruments were used to test for evidence of acquisition: an acceptability judgement task (AJT) and a productive gap-filling task (GFT). The AJT and GFT were conducted as pre-, post-, and delayed post-tests (three weeks after the post-test). A working memory (WM) task was also used to measure potential individual differences in processing capacity; prior proficiency levels were also taken into account in case of individual variation in progress during the intervention. A key finding was the improvement in the perfect have-en for the experimental group on the AJT and GFT over time. For the AJT, a significant long-term effect was found in the delayed post-test (at p < 0.05). For the GFT, the improvement was only significant at the first post-test (at p < 0.001). These findings suggest the treatment for the experimental group was effective, at least for comprehended knowledge. A few individuals displayed improvement in both comprehended and produced knowledge, although this did not seem to be dependent on prior proficiency. Thus, compared with traditional teaching that follows explicit textbook-based structural exercises, teaching the perfect have-en in a more communicative, linguistically- informed manner following FoF, can provide a more effective way of supporting instructed L2 acquisition, through understanding the impact of grammatical aspect and its relationship to tense in the acquisition process.
