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Face-gender discrimination modulated by attentional load
Leila Reddy, Patrick Wilken, Christof Koch

Recent work in our laboratory has shown that rapid natural-scene categorization (animal vs. non-animal) can be done with little or no attentional cost (Li et al.). For this study, we investigated the attentional cost associated with a task requiring fine discrimination of stimuli sharing similar features: discrimination of face gender. Subjects were required to perform a face gender discrimination task (face database obtained from MPI, Germany) either alone or concurrently with an attentionally demanding task (5-letter T/L discrimination). Both letters and images were masked following presentation ( SOA 106ms for faces, variable for letters, ranging from 173ms to 200ms). Face gender discrimination performance was significantly lower in the dual-task condition compared to the single-task condition, demonstrating that performance in this task is modulated by attentional load(Figure2). On the other hand, it is interesting to notice that percentage correct in the dual-task condition was still highly above chance level, implying that in the near absence of attention, observers can distinguish the gender of a face to some extent. This property is surprising from a computational point of view since subjects cannot distinguish between the letters T and L under precisely the same conditions, as shown recently in our group.

Figure 1. Normalized average performance for 3 subjects with 2 different image sets. Each point is a subject's average dual task performance normalized according to his/her single task performance. Normalized values are obtained by a linear scaling which maps the average single task performance to 100%, leaving chance at 50%. A significant decrease in performance is observed for each subject in the dual task condition compared to the single task condition. Image sets were randomly chosen from the face database used. Blue circles: image set 1, Red circles: image set 2.

References

Brain Areas Specific for Attentional Load in a Motion Tracking Task. Jovicich, J., Peters, R. J., Koch, C., Braun, J., Chang, L., & Ernst, T. (2001). (submitted)

Category-specific visual responses of single neurons in the human medial temporal lobe. Kreiman, G., Koch, C., & Fried, I. (2000). Nature Neuroscience, 3(9), 946-953.

Attentional capacity is undifferentiated: Concurrent discrimination of form, color, and motion. Lee, D.K., Koch, C., & Braun, J. (1999). Perception and Psychophysics, 61(7), 1241-1255.

Rapid Natural Scene Categorization Without Attention. Li, F., VanRullen, R., Koch, C., & Perona, P. (2001). (in preparation)

Tracking multiple independent targets: evidence for a parallel tracking mechanism. Pylyshyn, Z. W., & Storm, R. W. (1988). Spatial Vision, 3(3), 179-197.