Personal Names and the Attentional Blink: A Visual "Cocktail Party" Effect

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1 See discussions, stats, and author profiles for this publication at: Personal Names and the Attentional Blink: A Visual "Cocktail Party" Effect Article in Journal of Experimental Psychology Human Perception & Performance May 1997 DOI: // Source: PubMed CITATIONS 207 READS 1,445 3 authors, including: Kimron Shapiro University of Birmingham 132 PUBLICATIONS 8,139 CITATIONS Judy Caldwell Camosun College 7 PUBLICATIONS 397 CITATIONS SEE PROFILE SEE PROFILE All content following this page was uploaded by Kimron Shapiro on 06 August The user has requested enhancement of the downloaded file.

2 Journal of Experimental Psychology: Vol. 23, No. 2, Copyright 1997 by Ihe American Psychological Association, Inc /97/$3.00 Personal Names and the Attentional Blink: A Visual "Cocktail Party" Effect Kimron L. Shapiro, Judy Caldwell, and Robyn E. Sorensen University of Calgary Four experiments were carried out to investigate an early- versus late-selection explanation for the attentional blink (AB). In both Experiments 1 and 2, 3 groups of participants were required to identify a noun (Experiment 1) or a name (Experiment 2) target (experimental conditions) and then to identify the presence or absence of a 2nd target (probe), which was their own name, another name, or a specified noun from among a noun abstractor stream (Experiment 1) or a name distractor stream (Experiment 2). The conclusions drawn are that individuals do not experience an AB for their own names but do for either other names or nouns, hi Experiments 3 and 4, either the participant's own name or another name was presented, as the target and as the item that immediately followed the target, respectively. An AB effect was revealed in both experimental conditions. The results of these experiments are interpreted as support for a late-selection interference account of the AB. Visual information and visual attention are distributed over both spatial and temporal domains. Traditionally, research on visual attention has concentrated primarily on the spatial domain, with considerably less effort being devoted to the examination of temporal characteristics. More recently, however, attentional research has encompassed the temporal domain as well (Broadbent & Broadbent, 1987; Kanwisher & Potter, 1990; Shapiro & Raymond, 1994; Tipper, Weaver, Cameron, Brehaut, & Bastedo, 1991). The purpose of the present research was to use an old finding, the "cocktail party" effect, to examine a recently proposed theory of temporal attention. A procedure that has become widely used for examining the temporal characteristics of visual attention is rapid serial visual presentation. This technique involves the presentation of stimuli in rapid succession in the same spatial location. The participant's task usually involves the detection of one or more predefined targets. One finding consistently obtained with a dual-target task in rapid serial visual Kimron L. Shapiro, Judy Caldwell, and Robyn E. Sorensen, Department of Psychology, University of Calgary, Calgary, Alberta, Canada. Judy Caldwell is now at the Department of Psychology, University of Victoria, Victoria, British Columbia, Canada. Robyn E. Sorensen is now at the Department of Experimental Psychology, University of Cambridge, Cambridge, England. The funding for this research was provided by Natural Sciences and Engineering Research Council of Canada Grant OGP The studies were initiated in the laboratory of Kimron L. Shapiro by Judy Caldwell during her tenure there. We gratefully acknowledge the programming assistance provided by Bemie Weiser and Robert Ward. We also thank Jane Raymond for commenting on a draft of this article. Correspondence concerning this article should be addressed to Kimron L. Shapiro, who is now at the School of Psychology, University of Wales, Bangor, Wales LL57 2DG, United Kingdom. Electronic mail may be sent via Internet to k.shapiro@bangor. ac.uk. presentation studies is that participants experience difficulty detecting the second target if it is within a certain temporal window after the first. Broadbent and Broadbent (1987) were the first to demonstrate an interference effect in the detection of dual targets in rapid serial visual presentation studies. In their experiment, participants were asked to identify two target words designated by the presence of a hyphen on either side of the word. These researchers manipulated the lag between the two targets and demonstrated that identification of the first target made identification of the second target much more difficult when the two targets occurred in close temporal proximity, that is, within 400 ms. Weichselgartner and Sperling (1987) also found a deficit in a participant's ability to detect temporally proximal items. They presented a stream of digits and asked participants to identify a target digit (which was either highlighted or boxed) and the three digits that immediately followed it. Responses typically included the target, the digit occurring immediately after it, and the digits occurring approximately 350 ms after the target; digits occurring between 100 and 300 ms after the target were rarely identified. Shapiro and his colleagues (Raymond, Shapiro, & Arnell, 1992; Shapiro, 1994; Shapiro, Raymond, & Arnell, 1994) have conducted numerous rapid serial visual presentation studies and have replicated and expanded the findings discussed above. In their first series of experiments, Raymond et al. presented a stream of black letters in rapid serial visual presentation. The participant's task was to identify a target, which was a white letter, and then to detect the occurrence of a second target (referred to as the probe), which was a black letter X. The results of this experiment revealed a significant deficit in a participant's ability to report the probe when it occurred between 180 and 450 ms after the target. In an attempt to demonstrate that the difficulty in detecting the probe was not the result of sensory factors, Raymond et al. included a control condition in which participants were told to ignore the white target and just to 504

3 NAMES AND THE ATTENTIONAL BLINK 505 report the presence or absence of the probe. Participants were significantly more successful in detecting the probe in the control condition. Raymond et al. concluded that the findings could not be attributed to sensory effects but instead resulted from attentional factors. Furthermore, these researchers argued that the attenuated ability to detect the probe in this experiment could not be attributed to a memory problem, as might have been the case with Weichselgartner and Sperling's (1987) design, because the probe task required participants to recall only one item. Raymond et al. coined the phrase attentional blink (AB) to refer to the deficit in the detection of the second target. In an attempt to account for the findings of their experiments, Raymond et al. (1992) proposed an early-selection (cf. Broadbent, 1958) model. This model suggests that the target identification process, initiated by the occurrence of the target, is attentionally demanding, with a potential for confusion from the occurrence of the stimulus item immediately after the target (T+l item). The confusion was believed to arise from a potential conjunction error, as the target and the T+1 item confront the identification system with two identities and two colors (white from the target and black from the T+l item). In an attempt to avoid such confusion, the attentional system fully ceases processing information until the target identification process is complete. This cessation is the AB. Note that in this account the probe, per se, does not play a role in causing the AB. The model proposed by Raymond et al. (1992) is founded on a serial mechanism of information processing. The model explains information-processing limitations on the basis of attention being unavailable for the probe task because it is engaged with the target task. Because a serialprocessing mechanism plays a key role in an influential model of spatial visual search (e.g., Treisman & Gormican, 1988), it was reasonable to postulate that a similar mechanism underlies attentional limitations in the temporal domain. The assumptions underlying the serial model predict that the AB effect should be attenuated when the target task is less attentionally demanding. To examine this hypothesis, Shapiro, Raymond, and Arnell (1994) conducted a series of experiments examining the effects of various target manipulations. Such target manipulations included decreasing the target set size from 25 to 3 letters, requiring simply the detection (i.e., presence vs. absence) of a white letter 5, and requiring the detection of a random dot pattern. These manipulations yielded various degrees of target difficulty, as defined by d' values ranging from 2.05 (difficult) to 4.54 (easy), but none of these manipulations attenuated the AB as predicted. Despite the predictions of the Raymond et al. (1992) model, Shapiro, Raymond, and Arnell were forced to conclude that target task difficulty, per se, has little effect on AB magnitude. Lending support to an alternative conclusion are the results of two additional experiments done by Shapiro, Raymond, and Arnell (1994); in these experiments, the target task involved the absence of pattern information. In the first experiment, participants were asked to detect the presence of a temporal gap (characterized by the absence of a letter in the stream); in the second experiment, participants were asked to identify a long or short gap (characterized by the absence of one or two letters, respectively). Both experiments revealed d' values indicating that the target task was moderately to extremely difficult, yet both manipulations failed to yield an AB. Given the inadequacy of an early-selection model in accounting for these data, Shapiro, Raymond, and Arnell (1994) argued in support of a late-selection mechanism involving interference between the target and the probe during the retrieval process. Support for this hypothesis was found in the outcomes that any targets containing pattern information yielded ABs of similar magnitudes and that only targets without such pattern information failed to yield ABs. Interference-based explanations are usually predicated on late-selection models of attentional limitations. Such models suggest that multiple information sources may be encoded in parallel but that attentional limitations arise later in the system, when the demand from such sources exceeds attentional capacity (e.g., Kahneman, 1973). An alternative way to view such models is in terms of limitations arising when there is competition for the control of action systems (cf. Tipper, Lottie, & Bay I is, 1992). The ability to successfully process stimuli without interference thus becomes a function of available capacity and the demands made by each stimulus. The late-selection interference account offered by Shapiro, Raymond, and Amell (1994) and Shapiro and Raymond (1994) is based on a model suggested by Duncan and Humphreys (1989). Duncan and Humphreys's model was proposed as an alternative to the account of visual search provided by Treisman and Gormican (1988). Duncan and Humphreys proposed that target selection in spatial visual search is efficient to the extent that (a) targetnontarget similarity is minimal and (b) nontarget-nontarget similarity is maximal. Such "grouping" of targets and nontargets could be construed to maximize limited capacity by not requiring the allocation of attention to individual items in the display. Like that of Duncan and Humphreys (1989), our more recent model (Shapiro, Raymond, & Arnell, 1994) argues that the probe task becomes more difficult as the visual similarity between the target and the probe increases. This difficulty arises when similarity leads to interference among stimulus items that are in competition for entry to or retrieval from a short-term visual buffer (VSTM), in which such information is stored before retrieval. 1 The target and the probe are the primary contenders for this interference, but evidence (Raymond et al., 1992; Raymond, Shapiro, & Arnell, 1995) strongly suggests that the item immediately following the target and therefore likely the item immediately following the probe are competitors as well. An interference model such as that just described has proved more useftil in accounting for the findings reported by Shapiro, than has a model that does not take into account the role of the probe in producing the AB effect (cf. Ray- 1 Whether the hypothesized interference occurs for entry into a VSTM rather than for retrieval from a VSTM depends on to whose model one is referring and is beyond the scope of this article.

4 506 SHAPIRO, CALDWELL, AND SORENSEN mond et al., 1992). According to the interference model, both targets and probes containing pattern information should compete more with each other than either should with a target or a probe that does not contain pattern information. Thus, the model argues that whereas the difficulty of the target task does not affect AB magnitude, the degree of similarity between the target and the probe results in more or less of an AB effect. Note that at this stage in our thinking, we are suggesting a somewhat crude similarity mechanism, sensitive merely to patterned versus nonpattemed stimuli and not to subtle differences between patterned targets. Such a mechanism has the virtue of explaining the failure of target difficulty manipulations to affect the magnitude of the AB as well as the success in attenuating the AB effect with the use of a gap target in the Shapiro, Raymond, and Amell (1994) studies. It is tempting to use such a model to explain the finding reported by Ward, Duncan, and Shapiro (in press) that identical target and probe stimuli resulted in a more pronounced probe report deficit than did targets and probes that did not have identical pattern information, 2 but this explanation would contradict the crude similarity notion. Because a significant amount of research has been done to investigate the phenomenon in which participants fail to report a second, identical target and because various theories have been advanced to account for this outcome (cf. Kanwisher, 1987; Kanwisher & Potter, 1989, 1990), we do not engage in further such discussion in the present report. A model that is an alternative to the interference one proposed here and that suggests an object basis of attentional organization is discussed in the General Discussion section. Whereas an early-selection model suggests the role of the probe is passive, a late-selection model instead ascribes to the probe a more active role. The former suggests that the probe merely reveals processes initiated before its occurrence, whereas the latter suggests that the probe itself is involved in the production of the AB. A strong prediction of the interference model would be that any probe containing pattern information should yield an AB. However, it is possible that two patterned stimuli may not interfere with each other if the items can be distinguished by characteristics other than simple pattern features. In the first two experiments of this article, we therefore used a probe task in which the semantic content of the probe was varied in a manner used in earlier investigations of divided attention (see below). In the remaining two experiments, we used the same stimuli to test other predictions of the interference model. Using the dichotic listening paradigm, Cherry (1953) reported that individuals shadowing a message presented to one ear were completely unaware of the semantic information presented to the unattended ear. Broadbent (1958) suggested that such attentional limitations arise as a result of a selective filter serving to block certain information from further processing in order to facilitate the processing of other information. According to Broadbent, gross sensory information (e.g., pitch) from the unattended channel passes through the filter, but complex sensory information (e.g., meaning) does not. However, Moray (1959) was successful in replicating Cherry's findings with numbers and words but showed that if a participant's own name was presented to the unattended ear, the participant was able to successfully report its occurrence in a significant number of trials. This outcome has come to be known colloquially as the cocktail party effect and has been cited in numerous introductory psychology texts to suggest that certain items of semantic information cannot be filtered out. In an attempt to preserve Broadbent's (1958) filter theory, Treisman (1960) proposed that the filter is not an "all or nothing" mechanism but instead serves to attenuate rather than to block information from the unattended channel. According to her views, a node for a particular word in a mental "dictionary" possesses a threshold that must be exceeded for that word to reach "awareness." Information from the unattended channel is transformed in such a way as to make it less likely that the information will activate a particular node. Thus, only words with very low thresholds can be activated by the unattended channel. For example, words with high salience, such as fire or an individual's name, have thresholds for activation that are permanently lower than those for other words and can reach awareness even when presented to the unattended channel. The observations described above led us to hypothesize that a person's own name used as a probe may be less susceptible to interference from other items because of its lower threshold (higher salience). Lower diresholds may reduce interference by creating a stronger activation of the probe. Therefore, the first two experiments reported here represent an attempt to attenuate the AB by making die probe the participant's own name. In these experiments, the probe was the participant's own name, another person's name, or a noun. We hypothesized that a participant would successfully detect his or her own name but would be less successful at detecting either another person's name or a noun. In the first experiment, the participant had to detect the probes embedded in a stream of nouns, and in the second experiment, the participant had to detect the probes embedded in a stream of names. Method Experiment 1 Design. In this experiment, condition (control vs. experimental) and probe position (Positions 1-8) were repeated measures variables, and probe type (own name, other name, and noun) was a between-subjects variable. Participants. Twenty-seven students from the University of Calgary (12 women and 15 men) ranging in age from 17 to 43 years old, voluntarily participated in this experiment There were 9 participants for each of the three probe type conditions. Students 2 The finding of the more pronounced deficit when targets and probes were identical occurred only in the experimental condition in which the nontarget stream was present and therefore probably indicated that active selection of die target was an essential component contributing to the magnitude of the deficit. An appropriate interpretation of this finding is more complex than can be dealt with here.

5 NAMES AND THE ATTENTIONAL BLINK 507 who participated in the own-name probe condition had four-letter names. Stimuli and apparatus. The stimuli were generated by a Macintosh II computer and were displayed on an Apple 13-in. (~33-cm) color monitor. Participants were seated 42 cm from the screen in a partially darkened room, and a chin rest was used to stabilize head position. The stimuli were approximately 12 mm wide and 4 mm high and subtended visual angles of 1.64 in widdi and 0.55 in height. The words were presented at the same location in the center of a uniform gray field (9.1 cd/m 2 ). All words appeared in black, with the exception of the target item, which appeared in white (32.9 cd/m 2 ). Each word was presented for 60 ms, with an interstimulus interval of 15 ms. Procedure. Each participant took part in two sessions of 160 trials each (control and experimental), which were separated by a short break. The order in which the conditions were run was counterbalanced across participants. Each trial consisted of a series of successively presented uppercase four-letter words, as shown in Figure 1. The distractors were chosen at random by the computer from a set of 30 four-letter nouns. The target was 1 of 10 white nouns (different from the distractor nouns) chosen randomly by the computer. In the first probe condition, the participant's own name was the probe; in the second condition, the probe was another Fixation Spot Target Pre-target item Target A Single RSVP Trial Probe Pre-target items = 7-15 Post-target items = 8 Time > Post-target item Probe Figure 1. (A) Illustration of the stimuli included in the rapid serial visual presentation (RSVP) paradigm used in these experiments. The target was a white noun embedded in a stream of nouns. The probe was the participant's own name, another name, or a noun, presented at a variable serial position after the target (B) Illustration of the same stimuli shown in A but now revealing the temporal order of items. SOA = stimulus onset asynchrony; ISI = interstimulus interval. person's name (with the gender of the name being the same as the gender of the participant); and in the third condition, the probe was a noun. In this last condition, the same noun was used for all participants and was specified during the preexperiment instructions. The participants initiated each trial by pressing a mouse button. Each trial began with the presentation of a white fixation dot. The number of pretarget words presented varied randomly from 8 to 15, and the number of posttarget words was always 8. The probe was presented in half of the (rials, in 1 of the 8 posttarget positions. It never occurred before the target and was never presented more than once in the same stream. The probe was present 10 times in each of the 8 posttarget positions, yielding 80 probe-present and 80 probe-absent trials for each session. In the experimental condition, we asked participants to identify the white target word and to determine whether the probe was present or absent. In the control condition, we told participants to ignore the white target word and just to detect the presence or absence of the probe. Responses were repotted verbally to an experimenter, who entered them into the computer. Participants carried out 10 practice trials before each session. Results The mean percentages of trials in which the probe was correctly detected were calculated with only trials in which the target was identified correctly. Figure 2 shows the group mean percentage of trials in which the probe was correctly detected as a function of relative serial probe position for each of the three probe types. A Condition X Serial Probe Position X Probe Type analysis of variance (ANOVA) revealed a significant main effect of condition, F(l, 24) = , p <.01; a main effect of relative serial probe position, ^(7, 168) = 30.30, p <.01, and a main effect of probe type, F(2, 24) = 72.46, p <.01. The three-way interaction of Condition X Probe Position X Probe Type was also significant, F(14, 168) = 6.05, p <.01. To examine this interaction further, we carried out separate Condition X Serial Position ANOVAs for each of the probe types, using the Bonferroni adjustment to control the error rates. A significant Condition X Serial Position interaction would indicate that an AB had occurred; significance for this interaction was found in the noun probe condition, F(l, 49) = 14.32, p <.017, but not in the other-name condition, F(7, 63) = 2.26, p >.017, or the own-name condition, F(7, 56) = 2.78, p >.017. Although no AB was revealed in the other-name and ownname conditions, planned means comparisons demonstrated that the mean percentage of correct responses for Positions 2, 3, and 4 in the own-name condition was significantly greater than that for the same positions in the other-name condition, f(168) = 3.93, p <.01. The mean percentage of correct responses for these positions in the other-name condition was significantly greater than that for the same positions in the noun condition, f(168) = 21.18, p <.01. The individual false-alarm rates for probe detection ranged from 0 to 25% in the three probe conditions (see Table 1). Data showing false-alarm rates in excess of 2 SDs above the mean in this experiment and in the remaining experiments in this report were excluded from analysis. We

6 508 SHAPIRO, CALDWELL, AND SORENSEN Serial Probe Position Figure 2. Group mean percentage of trials in which the probe was correctly identified, plotted as a function of the relative serial position of the probe in Experiment 1. The stream consisted of four-letter nouns in all cases, exp = experimental conditions (participants had to identify the target and then detect the probe); cntl = control conditions (participants only had to detect the probe). performed a two-way Probe Type X Condition ANOVA on the false-alarm rates. A significant condition effect was found, F(l, 24) = 4.69, p <.05, with false alarms in the experimental condition (M = 13.06%) being more frequent than false alarms in the control condition (M = 6.94%). There was no significant difference in false alarms across probe types. Target errors for the three probe conditions ranged from 5 to 36.9% (M = 18.3%) in the own-name condition, from 6.3 to 45% (M = 20.1%) in the other-name condition, and from 6.3 to 26.9% (M = 16.3%) in the noun condition. An ANOVA of these rates yielded no significant differences. In this experiment and in the remaining experiments in this report, data for participants missing more than 30% of targets were excluded from analysis. Discussion The results of this experiment demonstrated the absence of an AB when the probe was the participant's own name and a significant attenuation of the AB when the probe was another person's name. A noun probe yielded the typical AB outcome (e.g., see Shapiro, Raymond, & Arnell, 1994). The results obtained with these two conditions represent potentially very significant findings and provide a clue to explain the AB effect, as all published attempts to use patterned stimuli to attenuate the AB effect have been unsuccessful (cf. Shapiro & Raymond, 1994). 3 Although the first finding was anticipated, the second was unexpected and raises the possibility of an alternative explanation for the results. Participants may have been able to detect the name probes (both their own and other names) because these probes were from a category different from that of the distractors. Furthermore, the near-ceiling effects revealed in the own-name and other-name control groups may have obscured our ability to observe an AB effect with these probe conditions. The purpose of the second experiment was to examine these possibilities. Experiment 2 In Experiment 2, a participant was asked to detect his or her own name, another person's name, or a noun within a stream of names. If the results of Experiment 1 can be explained by a category shift, then results similar to those obtained in the own-name and other-name conditions in Experiment 1 should be obtained in the noun condition in Experiment 2. We also hoped that the increased difficulty of the two critical probe tasks (own name and other name) in this manipulation would remove any concerns about ceiling effects in the control groups. Method Design. The design of this experiment was the same as that of Experiment 1, with condition (control vs. experimental) and probe position (Positions 1-8) being repeated measures variables and probe type (own name, other name, and noun) being a betweensubjects variable. Participants. Twenty-seven students from the University of Calgary (21 women and 6 men), ranging in age from 17 to 21 years old, voluntarily participated in this experiment. As in Experiment 1, there were 9 participants for each of the three probe type conditions. Students who participated in the own-name probe condition had four-letter names. Stimuli and apparatus. The stimuli and apparatus were identical to those used in Experiment 1, except that the distractor and target words were common four-letter names (half typically feminine names and half typically masculine names) instead of nouns. Procedure. The procedure used in Experiment 1 was also used in this experiment. In the first probe condition, the participant's own name was the probe; in the second condition, the probe was another name; and in the third condition, the probe was a noun. Unlike in Experiment 1, in which the same feminine or masculine name was used for all participants in the other-name condition, in the present experiment the names used in the other-name condition were matched to those of the participants in the own-name condition (e.g., if Bill was used in the own-name condition, then Bill was used in the other-name condition). In the noun condition, the same noun was used for all participants. In the experimental condition, 3 Experiments reported at the 34th annual meeting of the Psychonomics Society by Raymond, Caldwell, and Shapiro (1993) and by Shapiro, Moroz, and Raymond (1993) revealed factors other than pattern similarity that were able to attenuate the AB effect, but a discussion of these factors is beyond the scope of this article.

7 NAMES AND THE ATTENTIONAL BLINK 509 Table 1 False-Alarm Rates for the Probe in Each of the Probe Conditions in Experiments 1-4 Own name Other name Noun Experiment Experimental Control Experimental Control Experimental Control 1 M Range 2 M Range 3 M Range 4 M Range Note Data are reported as percentages we asked participants to identify the white target name, guessing if unsure, and to detect the presence or absence of the probe. In the control condition, we told participants to ignore the white target name and to state whether the probe was present or absent. Results The mean percentages of trials in which the probe was correctly detected were calculated with only trials in which the target was identified correctly. Figure 3 shows the group mean percentage of trials in which the probe was correctly detected as a function of relative serial probe position for each of the three probe types. A Condition X Serial Probe Position X Probe Type ANOVA revealed a significant main effect of condition, F(l, 24) = 90.60, p <.01; a main effect of relative serial probe position, F(7, 168) = 21.42, p <.01; and a main effect of probe type, F(2, 24) = 15.02, p <.01. The three-way interaction of Condition X Probe Position X Probe Type was also significant, F(14, 168) = 1.78, p <.05. We again analyzed this interaction further by performing separate Condition X Serial Position ANOVAs for each of the probe types, using the Bonferroni adjustment to control the error rates. A significant Condition X Serial Position interaction would indicate that an AB had occurred. As in Experiment 1, the Condition X Position interaction was not significant in the own-name condition, F(7, 63) = 1.98, p >.017, but was significant in the noun condition, F(7, 42) = 3.59, p <.017. However, whereas this interaction was not significant for the other-name condition in Experiment 1, it was significant for the other-name condition in this experiment, F(7, 63) = 10.50, p <.017. Thus, the primary difference between Experiments 1 and 2 was that no AB was found in the other-name condition with a abstractor stream of nouns, but an AB was found in the other-name condition when the stream consisted of names. In both stream conditions, no AB was found with the own-name probe condition, and a deep AB was found with the noun probe condition. In this experiment, the individual false-alarm rates for probe detection ranged from 0 to 28.75% in the three probe conditions (see Table 1). We performed a two-way Probe Type X Condition ANOVA on the false-alarm rates; no significant condition or probe type effects were found. Target errors for the three probe conditions ranged from 5 to 35.6% (M = 19.9%) in the own-name condition, from 6.9 to 28.8% (Af = 18.6%) in the other-name condition, and from 6.9 to 28.8% (M = 19.5%) in the noun condition. An ANOVA of these rates yielded no significant differences SO Serial Probe Position Figure 3. Group mean percentage of trials in which the probe was correctly identified, plotted as a function of the relative serial position of the probe in Experiment 2. The stream consisted of four-letter names in all cases, exp experimental conditions (participants had to identify the target and then detect the probe); cntl = control conditions (participants only had to detect the probe).

8 510 SHAPIRO, CALDWELL, AND SORENSEN The concern expressed in the Discussion section of Experiment 1 was that a ceiling effect might obscure our ability to observe an AB effect in the own-name and othername control groups. Although Figure 3 suggests that a similar problem may have existed in Experiment 2, we performed a number of analyses to counter this concern. First, we conducted a Serial Probe Position X Probe Type ANOVA for the control condition and found no differences among the control conditions for the three probe types. Second, we computed the 95% confidence interval on the basis of mean probe performance in the own-name control group, the group closest to the ceiling and for which a ceiling effect would be the most damaging to our central claim concerning the lack of an AB effect. At no position did the upper boundary of this interval reach 100%. Third, we performed for each participant a correlation analysis between overall AB magnitude (experimental condition) and probability of correct probe detection (control condition) in the own-name group. A significant correlation would suggest that more attenuation of the AB could be predicted by the ease of probe detection. A relatively minor correlation (r =.3) was obtained, making this assumption somewhat unlikely. Finally, the most compelling evidence was the failure to find a significant interaction in the ownname group when we performed a Serial Probe Position X Condition ANOVA. This lack of interaction suggests that there was no AB effect in this group. Thus, even if there were a ceiling effect in the control group, the lack of an AB effect in the own-name group stands in sharp contrast to the pronounced AB effect in the other-name and noun groups and in many studies by Shapiro and colleagues (Raymond et al., 1992; Shapiro, 1994; Shapiro, Raymond, & Arnell, 1994). Discussion The results of Experiment 2 were similar to those of Experiment 1. There was a complete attenuation of the AB effect in the own-name condition, but in the other-name and noun conditions, the AB effect was similar to that obtained in other studies (cf. Shapiro & Raymond, 1994). The only difference between Experiments 1 and 2 was evident in the other-name condition: Experiment 1 revealed an attenuation of the typical AB effect magnitude, but Experiment 2 did not. Although there may have been some benefit from category dissimilarity in the detection of a name (in contrast to a noun) probe when nouns were used as the distractor stream, this explanation can no longer fully account for the pattern of results seen in Experiment 2. The observed outcome that the own-name condition still did not reveal an AB effect even when the probe was detected from among categorically similar probes suggests that some other process must be going on. Further evidence that the effect was not attributable to category dissimilarity was revealed when the noun condition in Experiment 2 continued to reveal an AB effect, despite the difference in category. Experiment 3 The results of the first two experiments suggested that own-name probes do not yield an AB, even though othername and noun probes do. There are two possible accounts of this outcome. The first is that detecting one's own name is such an attentionally undemanding task as to put little drain on already taxed (i.e., by the target) attentional resources. On the basis of a simple capacity theory, such an account predicts that the use of one's own name as a target may yield a task so easy as to leave sufficient attention to attenuate the AB to any probe, assuming that target and probe tasks are reciprocally demanding of attentional resources. The second account of the failure of one's own name to yield an AB is based on the assumption that the target task demands a disproportionate amount of resources. Thus, even though a probe stimulus with a low threshold will survive the AB (e.g., one's own name), the same stimulus used as a target may nevertheless yield an AB to a different probe stimulus with a more typical threshold. A model incorporating this assumption and other necessary assumptions is proposed in the General Discussion section. The purpose of the next two experiments was to attempt to determine which of these two accounts is more valid. Method Design. The design of Experiment 3 was similar to that of the two preceding experiments, with the exception of the different target types. Thus, condition (control vs. experimental), probe position (Positions 1-7), 4 and target type (own name or other name) were all repeated measures variables. Participants. Eight students from the University of Calgary (5 women and 3 men), ranging in age from 18 to 33 years old, voluntarily participated in this experiment. Each student participated in all conditions. All students had four-letter names. Stimuli and apparatus. The stimuli and apparatus were identical to those used in Experiment 2, with the distractor words being common four-letter names (half typically feminine names and barf typically masculine names), the target being either the participant's own name or another name (feminine name for female participants and masculine name for male participants), and the probe being a noun (same noun for all participants). Procedure. The procedure used in the two preceding experiments was also used in this experiment, except that the two conditions (experimental and control) were completed by the same participants on separate days. In the experimental condition, we asked participants to identify the white target name and to detect the presence or absence of the probe (black noun). In the control condition, we told participants to ignore the white target name and to state whether the probe was present or absent. Results and Discussion The mean percentages of trials in which the probe was correctly detected were calculated with only trials in which 4 Only seven probe positions were used in Experiment 3 in an effort to reduce the total number of trials in which participants took part.

9 NAMES AND THE ATTENTIONAL BLINK 511 the target was identified correctly. Figure 4 shows the group mean percentage of trials in which the probe was correctly detected as a function of relative serial probe position for the two target types (own name and other name). A Condition X Serial Probe Position X Target Type ANOVA revealed a significant main effect of condition, F(l, 7) = 9.03, p <.05; a main effect of relative serial probe position, F(l, 42) = 6.49, p <.01; and a significant Condition X Serial Position interaction, F(7, 42) = 5.47, p <.01. The effect of target type (own or other name) was not significant. In this experiment, false-alarm rates for probe detection ranged from 0 to 15.7% over the two target types, with no significant differences between conditions (see Table 1). Target errors ranged from 0 to 14.3% in the two experimental conditions. Again, there was no significant difference between the own-name and other-name conditions. The results of Experiment 3 showed that both one's own name and another name yielded equal AB effects when these stimuli were used as targets in a rapid serial visual presentation task. When these same stimuli were used as probes (Experiments 1 and 2), the other-name condition revealed an AB, whereas the own-name condition did not. The results of Experiment 3 thus support the second of the two alternative theoretical accounts offered hi the introduction to this experiment. To reiterate, the data support the own name exp - - otter name exp own name cull other none end Serial Probe Position Figure 4. Group mean percentage of trials in which the probe was correctly identified, plotted as a function of the relative serial position of the probe in Experiment 3. The stream consisted of four-letter names in all cases, exp = experimental conditions (participants had to identify the target and then detect the probe); end - control conditions (participants only had to detect the probe). view that target and probe tasks play nonequivalent roles in the production of the AB. The role played by each of these tasks is discussed in the General Discussion section. Experiment 4 The interference model of the AB (Shapiro & Raymond, 1994; Shapiro, Raymond, & Arnell, 1994) suggests that, in addition to the roles played by the target and the probe, the T+1 item also plays a significant role in the production of the AB. Such a model was required by the empirical finding that removal of the T+1 item from the stream did not yield an AB effect (Raymond et al., 1992). Thus, Experiment 4 was designed to assess the role of the T+1 item by making it either the participant's own name or another name. If one's own name used as the T+l item is not attentionally demanding, as suggested by the first of the two possible accounts, then this condition should yield a pattern of results similar to that yielded by the condition in which the T+1 item is absent. Method Design. In Experiment 4, condition (control vs. experimental), probe position (Positions 2-7), 3 and T+l item type (own name or other name) were all repeated measures variables. Participants. Nine students from the University of Calgary (6 women and 3 men), ranging in age from 18 to 28 years old, voluntarily participated in this experiment. As in Experiment 3, each student participated in all conditions. All students had fourletter names. Stimuli and apparatus. The stimuli and apparatus were identical to those used in Experiment 3, with the distractor and target words being common four-letter names (half typically feminine names and half typically masculine names), the probe being a noun (same noun for all participants), and the T+1 item being either the participant's own name or another name (feminine name for female participants and masculine name for male participants). Procedure. The procedure used in Experiment 3 was also used in this experiment, with both conditions being completed on the same day. In the experimental condition, we asked participants to identify the white target name (from the list of 10 names used in Experiments 1, 2, and 3) and to detect the presence or absence of the probe (black noun). In the control condition, we told participants to ignore the white target name and to state whether the probe was present or absent. Results and Discussion The mean percentages of trials in which the probe was correctly detected were calculated with only trials in which the target was identified correctly. Figure 5 shows the group mean percentage of trials in which the probe was correctly detected as a function of relative serial probe position for the two T+l item types (own name and other name). A Condition X Serial Probe Position X T+1 Item Type 5 Six probe positions were analyzed in Experiment 4 because of the T+1 stimulus being fixed, as necessitated by the intent of this experiment.

10 512 SHAPIRO, CALDWELL, AND SORENSEN General Discussion Serial Probe Position Figure 5. Group mean percentage of trials in which the probe was correctly identified, plotted as a function of the relative serial position of the probe in Experiment 4. The stream consisted of four-letter names in all cases, exp = experimental conditions (participants had to identify the target and then detect the probe); end = control conditions (participants only had to detect the probe). ANOVA revealed a significant main effect of condition, F(l, 7) == 25.93, p <.01; a main effect of relative serial probe position, F(5, 35) = 10.35, p <.01; and a significant Condition X Serial Position interaction, F(5, 35) = 12.69, p <.01. The effect of T+1 item type (own or other name) was not significant. In this experiment, false-alarm rates for probe detection ranged from 0 to 31.7% over the two T+1 item types, with no significant differences between conditions (see Table 1). Target errors ranged from 5 to 32.5% in the two experimental conditions. Again, there was no significant difference between the own-name and other-name conditions. The results of Experiment 4 showed that both one's own name and another name yielded the same magnitude of an AB when used as T+l items. Because the T+l item has been shown to play a role in the production of the AB, we used the occurrence of the different T+1 items to test the plausibility of the two accounts of the AB outlined in the introduction to Experiment 3. The present results may be viewed as a refutation of the first of the two alternative accounts, as may the results of Experiment 3. That is, one's own name does not require such little attention as to exert no effect on the production of the AB. As mentioned earlier, the first alternative account might predict no AB effect, as was the case when the T+1 item was absent (Raymond et al., 1992), but an AB effect was clearly demonstrated in Experiment 4. Experiments 1-4 were designed to test predictions from the interference model purporting to explain the AB, as proposed by Shapiro and his colleagues (cf. Shapiro, 1994; Shapiro & Raymond, 1994; Shapiro, Raymond, & Amell, 1994), by use of the same target and probe stimuli hi different critical roles and relationships. This model predicts that the AB is caused by interference between the target and the probe and possibly also from the T+l item and the stimulus item that immediately follows the probe as they compete for entry to or retrieval from a VSTM. Although these experiments do not afford us the opportunity to resolve the entry versus retrieval issue, for argument's sake we adopt a position advocating an entry bottleneck. Perhaps most important, the results of these experiments confirm that the nature of the probe task is an important factor in the AB; participants were successful at detecting their own name as a second target (probe) in a rapid serial visual presentation stream but were significantly less successful at detecting either another person's name or a noun. These experiments also lead to the conclusion that a nonequivalent role is played by the target and the probe in the production of the AB. We showed that whereas the use of one's own name as a probe did not yield an AB, the use of the same stimulus as a target did yield an AB. The failure of one's own name used as the probe to yield an AB effect provides important additional evidence that the early-selection account proposed by Raymond et al. (1992) may not be an entirely adequate explanation for the AB. Instead, a late-selection account of our results may prove more satisfactory. As summarized in die introduction to this article, Moray (1959) showed that one's own name was able to survive a divided attention task. Treisman's (1960) account of this outcome argued that this special stimulus possesses a low threshold for recognition, enabling it to survive a weak foray into retrieval space by the unattended channel. A notion similar to Treisman's concept of threshold can be conjoined with the interference theory to account for our data. In conjunction with the finding of Shapiro, Raymond, and Arnell (1994) that targets without pattern information do not yield a detection deficit, we offer the following revised account of the AB. We propose that the presence of a visual target in the rapid serial visual presentation stream initiates an attentional episode into which the target and likely the T+l item are drawn. Such an episode engages an object identification mechanism for a substantial amount of time, by our estimates for as much as 500 ms. Other findings in support of this contention (e.g., Duncan, Ward, & Shapiro, 1994) indeed suggest that conventional models of serial visual search must be replaced by limited-capacity parallel models. After the occurrence of the target, the occurrence of the probe initiates a second attentional episode into which the probe and perhaps its immediate successor are drawn. Thus, the target and probe tasks result in four or possibly even more stimuli competing for entry into a VSTM. As proposed originally by Shapiro, Raymond, and Amell (1994) but elaborated on here, each competing stimulus

11 NAMES AND THE ATTENTIONAL BLINK 513 possesses a different weighting according to its salience, which is determined by a goodness-of-fit match between target and probe templates and the level of word logogen activation. Two candidate mechanisms are hypothesized to account for the reduced level of probe word logogen activation as a consequence of the target task. 6 The first candidate and perhaps the one most consistent with the interference hypothesis proposed by Shapiro and his colleagues (cf. Shapiro, 1994; Shapiro & Raymond, 1994; Shapiro, Raymond, & Arnell, 1994) argues in favor of the probe logogen being fully activated but decaying because of the passage of time commencing with the onset of target processing. A second but equally plausible candidate argues that the probe logogen is less than fully activated, again because of target processing preceding that of the probe. The latter is more of a perceptual explanation, whereas the former is more of a temporal decay account. The result, however, is the same insofar as the level of probe activation is reduced relative to that occurring in the control condition when the target is not attended. Reduced probe activation, for whatever reason, renders the probe more susceptible to interference from other processed stream stimuli. Thus, the critical difference between these two mechanisms is the degree of probe activation at the moment at which the probe is encountered. Stimulus salience, especially for words, is hypothesized to be determined according to these same rules but may be adjusted in the manner described by Treisman (1960). Treisman suggested that every word in her hypothetical construct of a dictionary possesses its own threshold. Successful recall of a word occurs only when its threshold is exceeded. The dictionary could be thought of as the goodness-of-fit matching criterion referred to above. In line with this notion, we suggest that certain words possess a permanently lower threshold (and thus a higher salience), as in the case of a person's own name or a signal for danger. We further argue that the consequence of this higher salience is less interference between the probe stimulus and other competing items in VSTM. The interference hypothesis just described is consistent with the finding that a temporal gap target judgment in the experiments of Shapiro, Raymond, and Amell (1994) did not yield an AB effect, because a target stimulus not containing pattern information would have been expected to reduce the potential for interference. 7 However, contrary to the specific predictions made by Shapiro, Raymond, and Arnell (1994), the present data suggest that not all targets and probes containing pattern information interfere with one another in such a way as to prevent probe detection. It appears that semantic content can effectively circumvent the interference normally created by two patterned stimuli. Similar findings of the importance of semantic content have been reported recently by Luck, Vogel, and Shapiro (1996); Maki, Frigen, and Paulson (in press); and Shapiro, Driver, Ward, and Sorensen (in press). Thus, a slight modification of the interference model as described above appears adequate to account for the data from both current and previous experiments. An interesting interaction worthy of brief discussion is the finding that other-name (as probe) targets did not reveal an AB when required to be detected from a noun stream (Experiment 1) but did reveal an AB when required to be detected from a name stream (Experiment 2). Noun probes, however, exhibited an AB regardless of whether they were detected in a noun or a name stream. 8 Although this interaction is worthy of experimentation, we venture the following account of this category effect The finding that noun probes showed an AB under all circumstances tested simply reveals the basic AB effect: After correct target identification, most probes surfer a reduced detection criterion for approximately 500 ms. The finding that other-name probes showed the AB effect only when searched for in a name (but not noun) stream suggests that other names possess a higher salience for detection than do nouns; such a salience difference, in combination with the category difference (names vs. nouns), may serve to explain the observed interaction. A finding consistent with this interpretation has been reported by Taylor & Hamm (in press). One's own name, by this same account, possesses an even higher salience allowing for its detection regardless of the distractor stream. 6 We thank Tom Can for a series of discussions that served to clarify this point of view. 7 Alternatively, a temporal judgment may be processed in a part of the brain not occupied with visual information processing, thereby circumventing interference for a completely different reason. 8 We thank an anonymous reviewer for drawing our attention to this point. References Broadbent, D. E. (1958). Perception and communication. London: Pergamon Press. Broadbent, D. E., & Broadbent, M. H. P. (1987). From detection to identification: Response to multiple targets in rapid serial visual presentation. Perception & Psychophysics, 42, Cherry, E. C. (1953). Some experiments on the recognition of speech, with one and with two ears. Journal of the Acoustical Society of America, 25, Duncan, J., & Humphreys, G. (1989). Visual search and stimulus similarity. 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