Research
Interests:
In many activities of daily life, we purposefully direct our attention toward a stimulus of interest. For example, suppose we are trying to console a distraught friend at a noisy party. The party activities may be very distracting, making it necessary for us to concentrate fully on each word spoken by our serious friend, while at the same time trying to ignore all of the party’s diversions. This is a task of selective attention. The research conducted in Dr. Melara’s laboratory investigates the psychological and physiological processes supporting selective attention in humans. These studies measure the psychophysical (signal detection, reaction time) and electrophysiological (event-related potentials) activity of human participants as they perform tasks of visual, auditory, or cross-modal selective attention. The goal of his research is to develop formal models of human attentional systems, models that explicitly link on-line physiological processing to momentary behavioral performance.
Currently, Dr. Melara is exploring four issues regarding selective attention.
1. Experience and training. Practice at focusing on task-relevant information and at ignoring task-irrelevant information enables humans to be efficient and accurate in performing cognitive tasks. Research in Dr. Melara’s laboratory demonstrates that both recent and past experiences can have dramatic and lasting effects on selective attention, altering both task performance and the electrophysiological responses of the brain. Experience-dependent changes in brain activity have been shown to persist for months after training.
2. Inhibitory processing. Selective attention involves not only focusing on targeted information, but also at disregarding distractor information. Suppressing distractors may involve an active inhibitory process in the brain. Dr. Melara and his colleagues have collected electrophysiological measures to distractors, tracking the time course and the magnitude of inhibitory activity. He has incorporated inhibitory processes into a formal model of attention effects in the Stroop task, a classic selective attention task in which observers focus on the colors of distracting color words (e.g., the word RED in green).
3. Working memory. Attention does not operate as a process unto itself. Attention can be strongly influenced by the information held in recent memory. A response to a current target can be affected by memory of a recent distractor. Dr. Melara has examined the characteristics of working memory that interfere with selective attention success. He finds that the discriminability of distractors in memory is a powerful force in disrupting attention to targets.
4. Cross-modal perception. When attending to targets in one sensory modality (e.g., vision), it often is relatively easy to ignore distractors in a different modality (e.g., audition). However, humans also easily recognize relations between the senses, such as between bright colors and high-pitched sounds. These are called synesthetic correspondences. Dr. Melara has explored how selective attention is affected by these cross-modal correspondences. He finds that, despite their metaphorical nature, such correspondences are recognized early, during the stages of perceptual processing.

Dr. Melara testing a participant in a selective attention task.
Recent
Publications
Melara, Robert D.,
Chen, Sufen, Wang, Huijun. (2005). Inhibiting change: Effects of
memory on auditory selective attention. Cognitive Brain Research,
25, 431 – 442.
Sabri, Merav; Melara, Robert D.; Algom, Daniel. (2004).
Neural correlates of auditory sensory memory and automatic
change detection. NeuroImage 21, 69– 74
Melara, Robert D.; Algom, Daniel,
(2003). Driven by Information: A Tectonic Theory of Stroop Effects. Psychological Review, Vol
110(3), 422-471
Melara, Robert D.; Rao, Aparna; Tong, Yunxia. (2002).
The duality of selection: Excitatory and inhibitory processes in auditory
selection attention. Journal of Experimental Psychology: Human Perception
and Performance, Vol 28(2), 279-306.
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