Conceived and designed the experiments: YW JT FF. Performed the experiments: JT ZM XG. Analyzed the data: JT ZM. Contributed reagents/materials/analysis tools: JT ZM. Wrote the paper: YW JT ZM FF.
The authors have declared that no competing interests exist.
By combining binocular suppression technique and a probe detection paradigm, we investigated attentional bias to invisible stimuli and its gender difference in both high trait anxiety (HTA) and low trait anxiety (LTA) individuals. As an attentional cue, happy or fearful face pictures were presented to HTAs and LTAs for 800 ms either consciously or unconsciously (through binocular suppression). Participants were asked to judge the orientation of a gabor patch following the face pictures. Their performance was used to measure attentional effect induced by the cue. We found gender differences of attentional effect only in the unconscious condition with HTAs. Female HTAs exhibited difficulty in disengaging attention from the location where fearful faces were presented, while male HTAs showed attentional avoidance of it. Our results suggested that the failure to find attentional avoidance of threatening stimuli in many previous studies might be attributed to consciously presented stimuli and data analysis regardless of participants' gender. These findings also contributed to our understanding of gender difference in anxiety disorder.
Generalized anxiety disorder (GAD) is an anxiety disorder that is characterized by excessive, uncontrollable and often irrational worry about everyday things, which is disproportionate to the actual source of worry
Cognitive theories about generalized anxiety disorders propose that patients or 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
Researchers usually used a dot-probe detection paradigm
Many studies have demonstrated that attentional bias could be induced by an unconsciously presented cue
This drawback can be overcome by another psychophysical method – binocular rivalry. When two incompatible pictures are presented to the two eyes that cannot be merged to a single visual percept, binocular rivalry occurs. Observer's perception switches back and forth between the two incompatible pictures, that is, they compete for perceptual dominance
We suspect that the failure to find attentional avoidance of threatening stimuli in many previous studies might be, at least partially, attributed to data analysis regardless of participants' gender. Many researches have indicated that there are gender differences in attention to and appraising of threat, which means females are more sensitive to threat-related cues than males and tend to overestimate the level of danger
In addition, many previous studies on attentional bias used an unbalanced gender ratio. For example, Koster et al.
In summary, the main object of our study is to examine attentional bias and its gender difference at unconscious level for both HTA and LTA individuals. We predict that, at unconscious level, only HTA females might exhibit an attentional bias towards fearful faces.
The experiment was conducted in accordance with general ethical guidelines in psychology. We have obtained written informed consent from all participants and the process was approved by the ethics committee in Peking University. In
HTAMean (SD) | LTAMean (SD) | df | t | P | |
Female | 56.67(11.18) | 28.58(7.08) | 22 | 7.35 | <0.001 |
Male | 58.50(11.29) | 26.33(9.32) | 22 | 7.61 | <0.001 |
Thirty-two images were selected from the Chinese Affective Picture System (CAPS)
Stimuli were presented on a 17-inch SAMSUNG monitor (1280×1024). The two eyes' images were displayed side-by-side on the monitor and fused using a mirror stereoscope mounted on a chinrest. A frame (10.7°×10.7°) that extended beyond the outer border of the stimulus and fixation point was presented to facilitate stable convergence of the two eyes' images. The viewing distance was 40 cm. Each trial began with fixation on a central cross (0.8°×0.8°) presented to each eye. In the invisible condition, a pair of identical high contrast dynamic noise patches was presented to the observer's dominant eye and a pair of intact and scrambled images to the non-dominant eye (see
The left image was presented to the non-dominant eye and the right image was presented to the dominant eye.
Total 256 trials were randomized across experimental conditions, including position of face image (left or right to the fixation point), position of the gabor probe (left or right to the fixation point), face emotion (fearful or happy), face gender (male or female) and visibility (visible or invisible). These trials were divided into four blocks, 64 trials for each block.
Before the experiment, participants practiced 50 trials for the invisible condition to get familiar with the experimental procedure. Those who reported seeing face images in the invisible condition were excluded from the experiment.
For the independent variables, the between-subject variables were group (high trait anxiety vs. low trait anxiety) and gender (female vs. male). The within-subject variables were emotion (fearful vs. happy) and visibility (visible vs. invisible). The dependent variable was the orientation discrimination accuracy of the gabor patch. The working hypothesis was that if there were attentional effects (either bias or avoidance) induced by the emotional pictures as a cue, the discrimination accuracy would be increased or decreased. We quantified attentional effect as the discrimination accuracy of the gabor probe presented at the position of the intact image minus the discrimination accuracy of the gabor probe presented at the position of the scrambled image, following the method in Jiang et al. (2006)
A positive value of attentional effect indicated attentional bias, which meant that attention was oriented toward emotional images, and a negative value indicated attentional avoidance, which meant that attention was oriented away from emotional images. Attentional effects were analyzed separately for the visible condition and the invisible condition, and the later one was one of the focuses of this study.
Attentional effects by happy and fearful faces in HTA and LTA groups are presented in
The results indicated no significant main effect or interaction. Error bars denote 1 SEM calculated across subjects.
Attentional effects by happy and fearful faces in HTA and LTA groups are presented in
The results indicated a gender difference of attentional effect induced by emotional pictures. And the gender difference of attentional effect was dependent on anxiety state. Error bars denote 1 SEM calculated across subjects.
A similar 2 (face emotion)×2 (anxiety state)×2 (gender) mixed-design ANOVA showed a significant interaction between emotion and gender (F (1, 44) = 6.59,
In
The experiment was conducted in accordance with general ethical guidelines in psychology. We have obtained written informed consent from all participants and the process was approved by the ethics committee in Peking University. Participants were also recruited from the pool of 1200 college students at Peking University. 18 HTA females and 18 HTA males participated in the experiment. The range of their age was 19–26 years, and their STAI-TAI scores were in
Female | Male | t | P | |
HTA | 52.83(9.77) | 52.83(6.64) | 0.00 | 1.00 |
Neutral face images were also from the Chinese Affective Picture System (CAPS)
A between-subject independent variable was gender (female vs. male). Within-subject independent variables were emotion (fearful vs. neutral vs. happy) and visibility (visible vs. invisible). Data were analyzed separately for the visible condition and invisible condition.
Attentional effects by neutral, happy and fearful faces in the HTA group were presented in
Female participants exhibited attentional bias to fearful faces, while male participants exhibited attentional avoidance of fearful faces. This result supported that there was gender difference in HTA population. Additionally, we did not find attentional effects by both neutral and happy faces. Error bars denote 1 SEM calculated across subjects.
No significant effects were found in the visible condition. In the invisible condition, the interaction of gender and emotion was significant (F (2, 33) = 5.6,
Using binocular suppression to render face images invisible, we found that invisible fearful faces could alter the distribution of spatial attention in HTA individuals. The attentional effect was gender-dependent. Specifically, HTA males showed attentional avoidance of invisible fearful faces, but HTA females showed attentional bias towards them. No significant attentional effect was found in the visible condition, in LTA individuals, and with neutral and happy face images.
Consistent with previous studies
In the invisible condition, HTA male participants exhibited attention avoidance of fearful faces, which can be considered to have some positive values. Recent models about attention to threat
Our study emphasizes two important issues in psychopathological researches. One is consciousness manipulation, the other is gender difference. Previous studies
We demonstrated the existence of gender difference in anxiety population and suggested the importance of balancing participants' gender in future studies. Previous studies used anxious participants with different ratios of genders, which generated distinctive conclusions. Our study adopted equal numbers of female and male participants and found significant, but different, attentional effects for each gender. Future studies should consider gender difference as an important factor in anxiety research.
In conclusion, we found attentional effects induced by fearful faces at unconscious level, and the effects were distinct for male and female participants. These findings may contribute to our understanding of gender difference in anxiety disorder.