Instructions and word bias in a lexical decision task

During a lexical decision task, identification of words is usually faster and more accurate than identification of nonwords. Normally, when instructions are presented to participants, an emphasis is placed on identifying words. The purpose of this study was to assess whether changing the instructions so emphasis is placed on identifying nonwords would change this word versus nonword effect. For 48 participants, 24 in the Word Instruction Type condition and 24 in the Nonword Instruction Type condition a significant word versus nonword main effect was found, but no interaction between type of instruction (word vs nonword focus) and type of item (word vs nonword). This indicates that participants' bias towards making word decisions may be very strong and may be based on prior experience and hence not easily affected by the kind of instructions given. Methodological issues for research are discussed.