دوره زمانی توجه برای تصاویر تهدید کننده در اضطراب خصلتی کم و زیاد

Cognitive studies about anxiety suggest that the interplay between automatic and strategic biases in attention to threat is related to the persistence of fear. In the present study, the time-course of attention to pictures with varying threat levels was investigated in high trait anxious (HTA, n=21n=21) and low trait anxious (LTA, n=22n=22) students. In a visual probe detection task, high and mild threat pictures were presented at three durations: 100, 500, and 1250 ms. Results indicated that all individuals attended to the high threat pictures for the 100 ms condition. Differential responding between HTA and LTA individuals was found for the 500 ms condition: only HTA individuals showed an attentional bias for mild threatening stimuli. For the 1250 ms condition, the HTA individuals attended away from high and mild threat pictures. The observed pattern of differential attention to threatening pictures may explain the persistence of fear in HTA individuals

In the last 20 years, there has been a strong interest in the cognitive processing of threat in high trait anxious (HTA) and low trait anxious (LTA) individuals. Cognitive theories about anxiety propose that HTA individuals have cognitive vulnerabilities at the level of attentive processing of threat that may maintain anxiety, and may even lead to the development of clinical anxiety disorders (Beck, Emery, & Greenberg, 1985; Eysenck, 1992; Williams, Watts, MacLeod, & Mathews, 1988). In particular, the interplay between automatic and strategic biases in attention to threat has been associated with the persistence of fear (Mogg & Bradley, 1998). A prominent idea about attentional processing of threat in HTA individuals is the “vigilance–avoidance” pattern (Mathews, 1990; Mogg, Mathews, & Weinman, 1987). HTA individuals initially attend to threat, but this is often followed by attentional avoidance of threat. It has been hypothesized that this pattern of vigilance and avoidance maintains anxiety. First, the initial vigilance for threat is responsible for the frequent detection of (potential) threat in the environment, and therefore results in frequent episodes of fear and anxiety. Second, attentional avoidance may lead to a short-term inhibition of fear and anxiety, but may—ironically—lead to more fear and anxiety in the long term. Indeed, attentional avoidance is related to brief exposure to threat and interferes with habituation to threat (Rachman, 1998). Although early cognitive models viewed attentional biases as essentially abnormal, more recent models of attention to threat (e.g., Eccleston & Crombez, 1999; Mathews & Mackintosh, 1998; Mogg & Bradley, 1998) have stressed the adaptive value of both initial attention to threat and strategic attentional avoidance. Initial attention to threat facilitates rapid response to danger and is an evolutionary hard-wired mechanism (see Öhman, Flykt, & Esteves, 2001). It is normal to direct attention to highly threatening (HT) information. Critical differences between HTA and LTA may, however, emerge when information is more ambiguous or only mildly threatening (MT). For instance, when walking through a city, big dogs may immediately attract the attention of HTA individuals, while LTA individuals will pay little attention to these animals. However, if a ferocious dog runs toward a person, barking aggressively, and showing its teeth, all individuals will immediately attend to this threat. In line with aforementioned models of threat, several studies observed that both HTA and LTA individuals selectively attended to HT pictures, and that only HTA individuals selectively attended to MT pictures (Mogg et al., 2000; Wilson & MacLeod, 2003). Other studies have repeatedly found that HTA individuals show an attentional bias toward MT information (e.g., threatening words) compared with LTA individuals (for reviews, see Mogg & Bradley, 1998; Williams et al., 1988). In some situations, attentional avoidance of threatening stimuli may also be adaptive. Obviously, stimuli outside the laboratory that are HT and require prompt action will not be avoided. However, when a threatening stimulus does not require immediate responding, attentional avoidance may be a strategy to maintain goal-directed behavior ( Eccleston & Crombez, 1999; Mogg & Bradley, 1998) or to regulate mood ( Ellenbogen, Schwartzman, Stewart, & Walker, 2002). Whether avoidance occurs, may critically depend upon the intensity of threat. If the threat value is low, individuals may not feel the need to avert their attention from the stimulus. It is possible that only stimuli with high threat value will elicit attentional avoidance. Research about the time-course of the vigilance–avoidance pattern has revealed mixed results, especially relating to attentional avoidance. In these studies often the visual dot probe task is used.1 In the dot probe task (MacLeod, Mathews, & Tata, 1986), a threatening and a neutral stimulus (words or pictures) are simultaneously presented at two different spatial locations on a screen. After the omission of this stimulus pair, a dot probe immediately appears at the location of one of the stimuli. The participant is required to respond to the location of the probe as fast as possible. Responding on trials where a probe follows at the same location as a threatening stimulus (“congruent” trial) is compared with responding on trials where a probe is presented at the opposite location of a threatening stimulus (“incongruent” trial). It is typically found that responding to probes on congruent trials is faster than to probes on incongruent trials, indicating that attention was located to the location of the threatening stimulus. Mogg, Bradley, de Bono, and Painter (1997) were one of the first to investigate the time-course of attention to threatening words in HTA and LTA. They used three presentation durations (100, 500, and 1250 ms). Results revealed no differential attentive processing of threatening words between HTA and LTA individuals at any of the presentation durations. A second study investigated the time-course of attention toward emotional faces (500 and 1250 ms; Bradley, Mogg, Falla, & Hamilton, 1998): an attentional bias toward threatening faces was found in HTA individuals for the 500 ms condition, but for the 1250 ms condition there was no difference in attention to threat between HTA and LTA individuals. Two recent studies, however, have found evidence for attentional avoidance in HTA individuals. First, in the eye-registration study of Rohner (2002) attentional avoidance of angry facial expression was found in HTA individuals at approximately 1500 ms. Second, in a recent study the time-course of attentive processing of pictures with varying threat levels (MT and HT) was examined in a dot probe task with two picture presentations: 500 and 1500 ms (Mogg, Bradley, Miles, & Dixon, 2004). In this study, further evidence was found for initial selective attention for HT pictures in HTA individuals. At the longer picture presentation there were no differences in attentive processing of threat between the HTA and LTA group. However, a blood-injury fearful subgroup of the HTA individuals showed attentional avoidance of HT pictures. The main objective of this study was to further explore the time-course of attention in a dot probe study. Our procedure was largely similar to the one of Mogg et al. (2004). There were some differences. First, we added a very brief picture presentation condition (100 ms). The 500 ms picture presentation of the Mogg et al. study may not be optimal to investigate automatic attentional biases, as it already allows several attentional shifts between locations. In the present experiment, three presentation conditions were used: 100, 500, and 1250 ms. Second, we wanted to investigate specific subcomponents of attention to threat because it may provide a more detailed understanding of the nature of attentional bias in HTA individuals. In the dot probe task, it is possible to differentiate between attentional capture by threat and the difficulty to disengage attention from threat (Koster, Crombez, Verschuere, & De Houwer, 2004). Attentional capture by threat is related to faster responding on congruent threatening trials than on neutral baseline trials. Disengagement difficulties are related to retarded responding on incongruent threatening trials in comparison with responses on neutral baseline trials. Several hypotheses were formulated based upon current models of attention to threat (Mathews & Mackintosh, 1998; Mogg & Bradley, 1998) and previous research (Mogg et al., 2000; Wilson & MacLeod, 2003). For the 100 and 500 ms condition, we expected to find selective attention to HT pictures in HTA and LTA individuals, and selective attention for MT pictures only in HTA individuals. For the 1250 ms condition, we had no clear hypotheses: The vigilance–avoidance hypothesis predicts stronger avoidance of threat in the HTA individuals. However, functional views on attentional avoidance predict that attentional avoidance of threat may be useful in regulating mood and, thus, will be observed in LTA as well as HTA individuals.