Centre for Visual Cognition, School of Psychology, University of Southampton, Southampton, United Kingdom.
J Exp Psychol Appl. 2010 Jun;16(2):133-44. doi: 10.1037/a0019569.
Previous studies have demonstrated a dual-target cost in visual search. In the current study, the relationship between search for one and search for two targets was investigated to examine the effects of target prevalence and practice. Color-shape conjunction stimuli were used with response time, accuracy and signal detection measures. Performance was lower in dual-target search compared with the combined performance for two independent single-target searches. The cost in response time slope disappeared with practice, but the cost in accuracy remained. Sensitivity was lower and the decision criterion more conservative in dual-target search than in single-target searches, suggesting that the representation of the target was less effective in dual-target search than in single-target search. Manipulation of target prevalence induced a bias in favor of the more likely correct response: target-present responses were likely under high target prevalence and target-absent responses were likely under low target prevalence. The prevalence effect was greater in dual-target search than single-target search, causing the dual-target cost to be larger under target prevalences that differed from 50%. These findings are important for applied tasks in which targets appear rarely and can differ from each other. For example, the low target prevalence in X-ray security searches may magnify the dual-target cost implicated in previous research with X-ray images (see Menneer, Cave, & Donnelly, 2009). Such a result would increase the need for security personnel to consider alternatives to dual-target search, such as specialization in detecting one target type or training to encourage independent searches for each target.
先前的研究已经证明了视觉搜索中的双重目标代价。在本研究中，我们调查了搜索一个和两个目标之间的关系，以检验目标出现率和练习的影响。使用颜色-形状联合刺激，并结合反应时间、准确性和信号检测测量指标来进行实验。与两个独立的单一目标搜索的综合表现相比，双重目标搜索的表现更低。随着练习，反应时间斜率的代价消失了，但准确性的代价仍然存在。在双重目标搜索中，敏感性更低，决策标准更保守，这表明在双重目标搜索中，目标的表示不如在单一目标搜索中有效。目标出现率的操纵诱导了对更可能正确的反应的偏好：在高目标出现率下，目标存在的反应更有可能，而在低目标出现率下，目标不存在的反应更有可能。在双重目标搜索中，这种流行效应大于单一目标搜索，导致在与 50%不同的目标出现率下，双重目标代价更大。这些发现对于应用任务很重要，因为在这些任务中，目标很少出现，并且彼此不同。例如，在 X 射线安全搜索中，目标出现的低流行率可能会放大先前研究中 X 射线图像所涉及的双重目标代价（参见 Menneer、Cave 和 Donnelly，2009）。这样的结果将增加安全人员考虑替代双重目标搜索的必要性，例如专注于检测一种目标类型或培训以鼓励对每个目标进行独立搜索。
