Abstract: It is widely reported that emotional negative stimuli are processed preferentially relative to positive and neutral stimuli. But there are also many other studies that do not find the processing differences between nega-tive and positive stimuli. This divergence might result from the different attention levels among studies. Some researchers suggest that when attention resources are extremely scarce, organisms can not respond discrimi-nately to negative and positive information. Thus, one may ask whether negative stimuli must be treated prefer-entially if plenty of attention is available.
The current study manipulated attention by a cue-target paradigm. In the valid cueing condition, subjects could obtain sufficient attention resources, while in the invalid cueing condition, resources were relatively insufficient. It was noteworthy that both attention levels in the current experiment were far greater than the attention scarceness that was mentioned before. Positive, neutral and negative pictures from the International Affective Picture System and the Chinese Affective Picture System were transformed into upper and lower adjacent patchworks of a normal scene and its inverted copy. Seventeen undergraduate students participated in the study. They were instructed to pay attention to the structure of the patchworks and to judge whether the normal scene was located in the upper or lower part of the whole patchwork. This implicit task was used to avoid the task relevance effect.
The behavioral data showed that the response accuracy in the valid cueing condition was significantly higher than that in the invalid cueing condition. Amplitudes of P1, N1, P2 and N2 components were also modu-lated by attention level. Significant interactions between emotion and attention were found in LPC difference waves. In the sufficient attention condition, there was no obvious difference between ‘positive minus neutral’ and ‘negative minus neutral’. In contrast, the LPC amplitude of ‘negative minus neutral’ was significantly larger than that of ‘positive minus neutral’ when the attention resource was relatively inadequate.
This study suggests that when enough attention resources are available, positive information can be proc-essed in the same way as negative information, i.e., negativity bias does not necessarily show up in circum-stances of sufficient attention. The processing superiority of negative events is more likely to take effect in situations where attention resources are not adequate. The phenomenon that emotional processing is modulated by attention is a manifestation of adaptation to environments. More work, such as manipulating attention sys-tematically to observe the influence on emotional processing, is needed to explore this issue further.

Key words: emotional negativity bias, attention, implicit emotional task, late positive component