n this chapter, we evaluate evidence from the past 25 years relevant to Snyder's (1975) andNeely's (1977) claim that words automatically activate their meanings, a claim recently called a myth (Besner, Stolz, & Boutilier, 1997;Stolz & Besner, 1999). According to Posner and Snyder's (1975) seminal treatment and some of the subsequent refinements made by Neumann (1984) and Bargh (1989Bargh ( , 1994, an automatic process (a) is fast acting, (b) is capacity free, (c) can occur without intention, (d) is involuntary or uncontrollable, and (e) can occur without conscious awareness. Although these five criteria were originally given equal weighting, they have not been examined to the same extent. Because of page limitations, we focus on whether semantic activation (SA) is capacity free and can occur without intention. We chose the former because it has not been extensively investigated and in our opinion may prove to be an informative area for future research. We chose the latter because it has been extensively used as a virtual litmus test for SA automaticity. (For more extensive treatments of the other criteria, see

Subjects named target words that followed a masked prime word of 33-msec (Experiments 1A and 1B) or 200-msec (Experiment 2) duration. The target word was either presented alone or accompanied by an interleaved distractor word. Targets presented alone were named more quickly following an identical prime than following an unrelated prime (repetition priming). In Experiment lA, targets with distractors were named more slowly following an identical prime than following an unrelated prime (negative priming), replicating Milliken, Joordens, Merikle, and Seiffert (Psycfwlogical Review, 1998). In Experiments 1B and 2, repetition priming was reduced, although not reversed, for targets with distractors. The results of all three experiments are opposite to the usual finding of enhanced priming for perceptually degraded targets and suggest that response conflict engages retrospective mechanisms that counteract the facilitatory effects of priming.If one either attends to a word or passively perceives it, reaction time (RT) is typically facilitated ifthe same word soon appears as a target for response (repetition priming). Responses to words or objects that are related to the initially perceived word are also likely to be facilitated (semantic priming or associative priming). However, if a word is deliberately ignored, responses to the same word, a related word, or a related object may subsequently be retarded relative to responses to an unrelated word or object (Neill, 1977;Neill & Westberry, 1987;Tipper & Baylis, 1987;Tipper & Driver, 1988; Vee, 1991). The latter effect, negative priming, has usually been demonstrated in selective attention tasks, in which target stimuli are accompanied by distracting stimuli. Thus, on a prime trial, the subject responds to a target while ignoring a distractor; negative priming occurs if the prime-trial distractor reappears as the target stimulus on a subsequentprobe trial. It has therefore been commonly assumed that negative priming is a consequence of selective attention to the prime-trial target.Selective attention on the probe trial also appears to be critical to negative priming. Although in some experiments negative priming has been found without distracting stimuli on probe trials (Neill, Terry, & Valdes, 1994;Neill & Westberry, 1987), the more typical finding is that negative priming is reduced (Moore, 1994) or even reversed (Lowe, 1979;Tipper & Cranston, 1985) for nonconflict probes. A series of experiments by Milliken and colleagues suggests that selective attention on the probe trial may in fact be sufficient to cause negative priming, Portions of this research were presented at the 37th Annual Meeting of the Psychonomic Society, Chicago, November 1996. We are indebted to Maria Cianciulli, Heather Clark, Jennifer Hein, and Christopher Nuzzi for assistance with data collection. We are also grateful to Bruce Milliken, Michael Kane, and an anonymous reviewer for helpful comments on our initial manuscript. Please direct correspondence to W. T. Neill, Department of Psychology, State U...

In a lexical decision task with two primes and a target, the target was preceded 300 msec by the second prime (P2) which in turn was preceded by a brief forward and backward masked first prime (PI). When PI and P2 were unrelated, reaction times were faster when the target was related to P2 (e.g., wave SALT ... pepper) than when the target was unrelated to P2 (and PI-e.g., wave LOAN ... pepper). However, this semantic priming effect was reduced to statistically nonsignificant levels when PI and P2 were repetitions of the same word. That is, priming did not occur for salt SALT . . . pepper relative to loan LOAN ... pepper. This reduction in priming was observed whether P2 and the target were strongly or weakly related. These findings raise problems for current accounts of semantic priming.Since Meyer and Schvaneveldt (1971) reported their seminal research, a large body ofwork has focused on delineating the mechanisms that underlie the semantic priming effect (see Neely, 1991, for a review). In the currently most popular version of this paradigm originated by Neely (1976), a person first silently reads a single prime word and then makes a speeded response to a target that appears after a brief delay. Semantic priming refers to the consistent finding that reaction times (RTs) to a target word are faster when it is preceded by a semantically related prime rather than an unrelated prime. ' The present research explores how semantic priming is affected by the prime itself being primed. The study most relevant to this issue was recently reported by BaIota and Paul (1996). They examined priming when two primes (1) were both related to the target and each other (e.g., copper bronze . . . METAL) or (2) were both related to the target but unrelated to each other (e.g., kidney piano ... ORGAN). In both cases, priming was enhanced, and to the same degree, relative to when only the second prime (P2) was related to the target and the two primes were unrelated to each other (e.g., order bronze . . . METAL or wagon piano . . . ORGAN).

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.

Masked repetition and semantic priming effects were examined in 2 experiments. In Experiment 1, a masked-prime lexical decision task followed a phase of detection, semantic, or repetition judgments about masked words. In Experiment 2 participants made speeded pronunciations to target words after they tried to identify masked primes, and the proportion of semantically and identically related prime-target pairs was varied. Center-surround theory CT. H. Carr & D. Dagenbach, 1990; D. Dagenbach, T. H. Carr, & A. Wilhelmsen, 1989) predicts positive repetition priming but negative semantic priming when people attempt, but fail, to extract the meanings of masked words. A retrospective prime-clarification account, in contrast, predicts that semantic and repetition priming effects will vary (being positive or negative) as a function of expectations about the prime-target relation. The data support a retrospective prime-clarification account, which, unlike center-surround theory, correctly predicted negative repetition priming effects.

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Five experiments demonstrate that when dots appear beside a briefly presented target object, and persist on view longer than the target, the flanked object is perceptually altered by the dots. Three methods are used to explore this object trimming effect. Experiments 1-3 assess participants' conscious reports of trimmed digits, Experiment 4 uses repetition priming to explore the target representation, and Experiment 5 examines the perception of apparent motion in trimmed targets. Results of all three methods indicate that object trimming is influenced by mechanisms of perceptual grouping that operate on target representations prior to conscious access. Separate contributions from visual crowding and backward masking are also identified. These results imply that common-onset masking does not always result from the target being substituted by the mask, but that target and mask can sometimes maintain separate mental representations.

A four-dot mask that surrounds and is presented simultaneously with a briefly presented target will reduce a person's ability to identity that target if the mask persists beyond target offset and attention is divided (Enns & Di Lollo, 1997, 2000). This masking effect, referred to as common onset masking, reflects reentrant processing in the visual system and can best be explained with a theory of object substitution (Di Lollo, Enns, & Rensink, 2000). In the present experiments, we investigated whether Gestalt grouping variables would influence the strength of common onset masking. The results indicated that (1) masking was impervious to grouping by form, similarity of color, position, luminance polarity, and common region and (2) masking increased with the number of elements in the masking display.