The role of monitoring and control in similar nontarget/target discrimination

Processes involved in discrimination of targets from nontargets differing by a single critical feature were explored. Participants learned 80 target nouns (singular and plural), and were tested on 120 nouns: 40 targets, 40 similar nontargets (plurality changed between study and test), and 40 novel nontargets. Speeded (250ms, 1000ms) yes-no judgments were required after each test item. In Experiment 1, participants were informed before study, or after study but before recognition, that the test contained nontargets similar to targets by virtue of a plurality change. Controls received no such instructions. Target/nontarget similarity instructions reduced false alarms to similar nontargets and enhanced discrimination only when participants were informed before study, and at the 1000ms response interval. In Experiment 2, one group of participants was oriented to the specific discriminating feature before study, while another group was instructed that the task was difficult and to invest considerable effort at study. Specifically orientating participants to the critical feature change again improved discrimination and reduced false alarm rates, while merely emphasizing the requirement for effortful encoding did not. Detailed monitoring and control of target/nontarget discrimination are effective in reducing false recognition only if the necessary discriminating features are deliberately encoded at study, and if sufficient time is given for deliberate retrieval at test