An evaluation of early and late stage attentional processing of positive and negative information in dysphoria

Abstract

Depressive disorders may be characterised by hyperattention toward negative information, hypoattention toward positive information, or a combination of both processing biases. In two studies, a dot-probe task was utilised to better ascertain the specific direction and time-course of these biases. In both studies, the dysphoric group showed significantly less attentional allocation toward positive stimuli than the non-dysphoric group. In study two, the dysphoric group also showed greater attentional allocation toward depression-specific stimuli. Importantly, the bias toward depression-specific stimuli, and the bias away from positive stimuli, were uncorrelated with each other. It may be that both biases can act as sufficient, but not necessary, characteristics of dysphoric processing. An additional possibility is that the relative level of each bias type may best characterise dysphoric processing. Each of these possibilities is discussed in turn.

Acknowledgements

This research was supported by the Social Sciences and Humanities Research Council of Canada.

We gratefully acknowledge Chad Ebesutani and Laura Elinson for their help with data collection, and a number of anonymous reviewers for their excellent feedback.

Notes

¹It is important to recognise the benefits and drawbacks of our approach of using positive − neutral and negative–neutral trials, rather than integrated positive–negative trials. As was pointed out by an anonymous reviewer, our use of separate positive–neutral and negative–neutral trials could serve to minimise a true correlation between positive and negative attentional biases. While acknowledging this, given that not all situations need be characterised by the presence of both positive and negative stimuli, and because almost no situation (and perhaps no situation) could be characterised by the presence of only positive and negative stimuli, use of mixed positive-negative trials in the absence of any non-valent stimuli, could cause an equal enhancement of the true correlation. Future research would benefit from a careful analysis of the benefits and drawbacks of each approach.

²Before calculating attentional bias scores, we entered the raw RT data into a 2×2×2×2×2 ANOVA with valence (positive, negative), duration (500 ms, 1500 ms), picture location (left, right), and probe location (left, right) as within-subject variables, and dysphoria (high, low) as a between-subject variable. Significant main effects of picture location, F(1, 70) = 7.97, p<.01, duration, F(1, 70) = 178.25, p<.001 and valence, F(1, 70) = 88.30, p<.001 were identified. Of particular note, the predicted four-way interaction of dysphoria × valence × picture location × probe location reached significance, F(1, 70) = 4.83, p=.03, which provided the basis for the calculation of the attentional bias scores used in the remainder of the analyses. The five-way interaction involving duration did not reach significance, F(1, 70) = 1.46, p>.2.

³Interpretation of these covariate analyses need be made with caution. Miller and Chapman (2001) have pointed out that using a covariate that is highly correlated with the measure of interest may regress out substantial variance, and may leave a variable with little in common with the original construct. With appropriate caution, we believe these covariate analyses remain useful, however, we also believe it important to note these issues of interpretation.

⁴For these continuous analyses, all participants including those with BDI scores between 6 and 10 were included in the analyses. Results remained similar when excluding this group, however, the nature of continuous analyses required inclusion of the full sample of participants.

⁵Once again, before calculating attentional bias scores, we entered the raw RT data into a 2×2×2×2×2 ANOVA with valence (positive, negative), duration (200 ms, 1500 ms), picture location (left, right), and probe location (left, right) as within-subject variables, and dysphoria (high, low) as a between-subject variable. Significant main effects of duration, F(1, 63) = 479.80, p<.001, and valence, F(1, 63) = 15.01, p<.001 were identified. The predicted four-way interaction of dysphoria×valence×picture location × probe location reached significance, F(1, 63) = 9.93, p=.002, which provided the basis for the calculation of the attentional bias scores used in the remainder of the analyses. The five-way interaction involving duration did not reach significance, F(1, 63) = 1.66, p=.20.