Backward priming was examined at 150-and 500-msec prime-target stimulus onset asynchronies (SOAs) using visually presented primes and targets in lexical decision and pronunciation tasks. Two kinds of backward relations were used: compound items for which targets and primes formed a word in the backward direction (e.g., prime: HOP; target: bell), and noncompound items for which targets and primes did not form a word but were associatively related in the backward but not the forward direction (e.g., prime: BABY;target: stork). Results showed that backward priming effects were equivalent for compounds and noncompounds. However, for lexical decisions, backward priming occurred at both SOAs, whereas for pronunciation, it occurred only at the 150-msec SOA. We discuss how this SOAdissociated backward priming effect in lexical decision and pronunciation tasks poses a serious challenge for all theories of semantic priming.Numerous studies have examined how a single-word semantic context (called the prime) can affect the processing ofa following target letter string (see Neely, 1991, for a review). To allow control over the stimulus onset asynchrony (SOA) between the prime and target, in most semantic priming experiments no overt response is required to the prime and the person's task is either to make a lexical (word/nonword) decision to the target or to pronounce it aloud, as quickly as possible. The finding that reaction times (RTs) to a target are faster when it follows a semantically or associatively related prime than when it follows an unrelated prime is referred to as semantic priming.

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