Many linguistic studies have been conducted as a reaction to this never-ending bewilderment at people's ability to acquire or learn two or more languages. This gave rise to Psycholinguistics as a major field of linguistics that explains the difficulties faced by learners of L2 during their long tiring journey of L2 acquisition. The present paper investigates the relation between psycholinguistics and Second Language Acquisition (SLA) in general, and the way learners of L2 acquire tense-aspect in particular. It addresses the following questions: (1) What are the most commonly occurring English L2 language errors in the writing of Egyptian students with Arabic L1 language? (2) How can these errors be accounted for? (3) Does the acquisition of tense-aspect as a grammatical and lexical category by L2 learners foster these errors? (4) To which extent is the way learners of L2 acquire tense-aspect as a grammatical and lexical category affected by L1 interference? The data used in this paper come from 68 university students studying at the Department of English in Mansoura University. Learners have been requested to provide free composition writing, and a corpus of 184 structures was collected to analyze the source of verbs, verb types, functions and form associations. Results were discussed in the light of Error Analysis. The study concludes that learners tend to follow similar processing techniques no matter what language is being acquired; this gives rise to Transfer, and hence to written errors