بررسی جانبداری پردازش اطلاعات در عنکبوت هراسی با استفاده از پارادایم سریع ارائه بصری سریالی

Empirical research has demonstrated the existence of attentional biases towards threat in anxiety disorders. Paradigms commonly used to assess attentional biases have failed to demonstrate consistent findings as well as reveal the specific features of attentional biases. The current study investigated the utility of the rapid serial visual presentation paradigm in assessing attentional biases among 40 undergraduate students with high spider phobia (SP) symptoms and 40 undergraduate students with low SP symptoms. Results revealed that across participants, threatening information was processed in a facilitated and automatic manner and resulted in an immediate (i.e., within 120 ms) attentional capture. Following immediate attentional capture, however, only high SP participants exhibited an attentional alertness towards subsequent stimuli following threat presentation. These results extend traditional attentional bias literature, and theoretical implications are discussed.

Contemporary models of anxiety (e.g., Beck & Clark, 1997; Mogg & Bradley, 1998) posit cognitive biases towards threat. Additionally, these observed cognitive biases have been theorized to be a process by which anxiety disorders are maintained (Amir, Elias, Klumpp, & Przeworski, 2003; Mogg & Bradley, 1998). Cognitive biases have been observed in the domains of interpretation (Becker & Rinck, 2004; Brendle & Wenzel, 2004), memory (Coles & Heimberg, 2002; Sawchuk, Lohr, Lee, & Tolin, 1999), and particularly frequently in attention (e.g., Amir, Coles, & Foa, 2002). Attentional biases in anxiety have commonly been observed in empirical research using a modified Stroop task (Stroop, 1935). In this experiment, participants are presented with anxiety related words displayed in varying colors. Participants are asked to ignore the semantic content of the word and verbally report the color as fast as possible without sacrificing accuracy. Attentional biases are inferred from increased response latencies towards anxiety related words compared to response latencies towards neutral-valenced words. Attention is theorized to be immediately allocated to the threat stimulus, which interferes with the color-naming task and subsequently results in heightened response latencies (e.g., Bryant & Harvey, 1995). The attentional bias as demonstrated through higher response latencies in the Stroop task has been found across anxiety disorders, including posttraumatic stress disorder (PTSD; Bryant & Harvey, 1995; McNally, Kaspi, Bradley, & Zeitlin, 1990), generalized anxiety disorder (GAD; Becker, Rinck, Margraf, & Roth, 2001), social phobia (McNeil, Ries, Taylor, & Boone, 1995), snake phobia (Wikstrom, Lundh, Westerlund, & Hogman, 2004), and panic disorder (PD; Buckley, Blanchard, & Hickling, 2002). Additionally, research suggests that attentional biases identified in the Stroop task are towards threat stimuli relevant to the diagnoses, as opposed to threat in general (e.g., Becker et al., 2001), albeit inconsistently (e.g., Buckley et al., 2002). Another common paradigm with which attentional biases are investigated is the dot-probe paradigm (MacLeod, Mathews, & Tata, 1986). In the original version of the task (MacLeod et al., 1986), two stimulus words are presented, one above the other, on a computer screen for 500 ms. Participants are asked to read the top word, thus necessitating attentional allocation to the top word and not the bottom word. A probe then replaces either the top or bottom word and the participants are instructed to press a key as soon as they detect the presence of the probe. Attentional biases are inferred from faster response times towards probes replacing threat words compared to probes replacing other word types. Later versions of the task (e.g., Koster, Crombez, Verschuere, & De Houwer, 2004; Mogg, Bradley, Bono, & Painter, 1997) do not require the participant to read the top word and instead the participant determines in which location, top or bottom, the probe occurs. Research using versions of this paradigm have also identified attentional biases across anxiety disorders, including PD (e.g., Horenstein & Segui, 1997), GAD (e.g., Bradley, Mogg, White, Groom, & de Bono, 1999), social phobia (e.g., Pishyar, Harris, & Menzies, 2004), and PTSD (e.g., Bryant & Harvey, 1997). The Stroop and dot-probe literature support the existence of attentional biases. Researchers have more recently begun to investigate the specific features of attentional biases. Using the Stroop task and other cognitive measures, researchers have attempted to distinguish between automatic and strategic processing, and also to differentiate facilitated attention to threatening stimuli versus difficulty in disengagement from threatening stimuli. The studies mentioned thus far have used the unmasked Stroop task, in which the stimuli appear continuously until the participants respond. The masked Stroop task, however, presents the stimulus word quickly (e.g., 20 ms) and is backwardly masked by another stimulus in order to preclude conscious and strategic semantic processing. Buckley et al. (2002) hypothesized that the masked Stroop task exclusively assesses automatic processing; the unmasked condition, however, presents the stimulus word for an extended period of time, which allows both initial automatic processing and further semantic and strategic processing. Assessing Stroop task performance in the masked versus unmasked condition has been one avenue through which strategic versus automatic processing has been investigated. This line of research has yielded equivocal results. Some studies have found strategic, but not automatic processing, in snake phobia (e.g., Wikstrom et al., 2004), social phobia (e.g., Amir et al., 2002), PTSD (e.g., Bryant & Harvey, 1995), and PD (Buckley et al., 2002). In contrast, some studies have found both automatic and strategic processing in GAD (Bradley, Mogg, Millar, & White, 1995), PTSD (Harvey, Bryant, & Rapee, 1996), spider phobia (van den Hout, Tenney, Huygens, & de Jong, 1997), and also in elevated trait anxiety (van Honk et al., 2001). There appears to be a consistent finding of strategic processing biases and a less robust finding of automatic processing biases. Similar to the dilemma of distinguishing whether attentional biases are automatic, strategic, or both, there is also a dilemma of distinguishing whether the characteristics of attentional biases are comprised of facilitated attention to, or difficulty disengaging attention from, threatening information. On one hand, increased response latencies in the Stroop task may occur because threatening semantic information draws attention away from the color (i.e., facilitated attention). On the other hand, the observed increased response latencies may occur because of difficulty removing attention from threatening semantic content. Both stimuli may be processed and attended to in a similar fashion (i.e., no facilitated attention towards threat), but it is difficult to disengage attention from threat. This line of research has also yielded equivocal results. Studies using various assessment tasks (e.g., visual search, Posner, and odd-one-out tasks) reveal difficulty in disengagement and no facilitated attention (e.g., Amir et al., 2003; Fox, Russo, Bowles, & Dutton, 2001; Rinck, Becker, Kellermann, & Roth, 2003), facilitated attention but no difficulty in disengagement (Pflugshaupt et al., 2004), and evidence of both facilitated attention and difficulty in disengagement (Byrne & Eysenck, 1995; Miltner, Krieschel, Hecht, Trippe, & Weiss, 2004; Rinck, Reinecke, Ellwart, Heuer, & Becker, 2005). Research investigating the specific features of attentional biases has yielded equivocal results. Failure to find consistent results is not the only limitation in attentional bias research. Another limitation is that the paradigms used most frequently have occasionally failed to detect the existence of attentional biases in the Stroop (Devineni, Blanchard, Hickling, & Buckley, 2004; Moritz et al., 2004 and Sawchuk et al., 1999) and dot-probe tasks (Horenstein & Segui, 1997; Wenzel & Holt, 1999). These studies highlight the inconsistencies in demonstrating attentional biases. A probable explanation is that the current paradigms used to assess attentional biases lack sensitivity to consistently identify the existence of attentional biases. This inadequacy of paradigms used to assess attentional biases is a third limitation in attentional bias research. The paradigms traditionally employed (Stroop, dot-probe, Posner, homograph, and visual search tasks) use behavioral response latency as a dependent measure. This is an indirect measure of attention: using the latency between stimulus onset and behavioral response as an indicator of attentional processes assumes that nothing else is occurring during that latency which could also account for the latency. Investigating attentional biases with a new paradigm that does not have the same limitations as traditional paradigms is a necessity in attentional bias research. One possible paradigm is the rapid serial visual presentation (RSVP) paradigm, a paradigm from the cognitive-experimental literature (e.g., Raymond, Shapiro, & Arnell, 1992). In this paradigm, a stream of approximately 20 stimuli (e.g., words, letters, numbers) is presented on a computer screen such that a subsequent stimulus replaces the previous stimulus, all stimuli appear in the same location, and all stimuli appear for the same duration (approximately 100 ms). At some point in the stream (usually 8–11 stimuli into the stream), a target stimulus appears. This word usually appears in a different color from the other stimuli, thus making it stand out, and can vary across trials. At some point in the stream following the target, a probe may occur. The probe appears in the same color as the distracter stimuli and remains constant across trials. The probe can appear in one of nine probe positions (i.e., probe position 1 means the probe directly follows the target, probe position 2 means that the probe appears with one distracter item between the target and probe, etc.). There are two conditions in the RSVP paradigm: control and experimental. In the control condition, participants are told to ignore the target stimulus and only asked to detect the presence of the probe. Detection of the probe usually occurs with approximately 95 percent accuracy in all probe positions (e.g., Shapiro, Caldwell, & Sorensen, 1997). In the experimental condition, participants are asked to identify the target stimulus and also detect the presence of the probe. Relative to the control condition, accuracy of probe detection in the experimental condition in positions 2–5 is decreased following target identification. The decrease in performance in the experimental condition relative to the control condition is termed an attentional blink (AB). The control condition shows that when not attending to the target, probe detection accuracy is nearly perfect; therefore, the probe detection deficit observed in the experimental condition is due to identification of the target. The RSVP paradigm experimentally manipulates the latency between the onset of the target and the probe and measures the accuracy at which the probe is detected following target identification. This paradigm allows an investigation of the accuracy at which probe detection occurs as a function of the latency between the two stimuli (e.g., accuracy at 120 ms after the target versus accuracy at 240 ms after the target). This is in contrast to traditional paradigms that measure speed of behavior, and thus the RSVP measures information processing via experimental manipulation instead of through traditional response latency. As such, the RSVP paradigm offers a new avenue through which to assess attentional biases that does not have the limitations of traditional attentional bias assessments. Currently, there are three articles investigating the effect of an anxiety related stimulus on the size of the AB. Arend and Botella (2002) found that emotional target words (e.g., thief) reduced the attentional blink among high-trait anxious individuals compared to low-trait anxious individuals. Ogawa and Suzuki (2004) manipulated the valence of the probe using non-clinical participants and found that detection of negatively valenced probes was equal in the experimental and control conditions. In other words, the AB was eliminated in the negative probe condition. Keil and Ihssen (2004) used a modified RSVP procedure in which participants were asked to identify two target words appearing in green that occur within a stream of distracters. Results indicated that target 1 identification was not affected by emotionality, but target 2 identification was greater for emotionally charged words. Results of these studies have implications for attentional bias research. As mentioned, the traditional paradigms used to assess attentional biases measure the latency of a behavior. Results from the RSVP literature indicate that when the latency between a threatening and neutral stimulus is experimentally manipulated while the accuracy of detection of the neutral stimulus is measured as a function of its temporal proximity to the threatening stimulus, the opposite of traditional attentional biases is found. Data from the Stroop, dot-probe, Posner, visual search, and homograph tasks show that attention is either drawn to or captured by threatening stimuli, and data from these bodies of literature would indicate that in the RSVP paradigm, attention would be captured by the target word and subsequently attenuate probe detection. Ostensibly opposite results were found in the anxiety-RSVP literature. These three anxiety-RSVP studies suffer from two main limitations. First, Arend and Botella (2002) did not include the control condition of the RSVP, which is important in operationally defining the AB. Second, samples were either non-clinical or trait-anxious, and as such, it cannot be clear that the threatening stimuli used in the studies adequately sampled from the participants’ domains of fear. Because of these limitations in the anxiety-RSVP literature, the present study investigated RSVP performance in individuals with low and high symptoms of an anxiety disorder with a limited domain of threat. Due to the inferential nature of traditional attentional bias paradigms as well as the evidence from the anxiety-RSVP literature, it is hypothesized that high-anxious individuals have a shorter AB compared to non-anxious individuals. If results from this study also indicate a shorter AB, it will provide adequate evidence with which to discuss possible explanations for why traditional attentional bias paradigms have different results than findings from the anxiety-RSVP literature.