Microsaccadic responses in a bimodal oddball task

In a visual oddball task the presentation of rare targets induces a prolonged microsaccadic inhibition as compared to standards. Here, we replicated this effect also in the auditory modality. In addition, although auditory standards induced a more limited modulation of microsaccadic frequency as compared to visual standards, auditory oddballs induced a prolonged microsaccadic inhibition. With bimodal standard stimuli the microsaccadic response was determined by the attended modality, resembling that produced by attended unimodal stimuli. The present findings support the idea that the microsaccadic response to oddball and standard stimuli is partly driven by cognitive mechanisms common to both the visual and the auditory modality, and that microsaccades can be used as an implicit behavioral measure of ongoing cognitive processes.     

The speed and accuracy of material recognition in natural images

We studied the time course of material categorization in natural images relative to superordinate and basic-level object categorization, using a backward-masking paradigm. We manipulated several low-level features of the images—including luminance, contrast, and color—to assess their potential contributions. The results showed that the speed of material categorization was roughly comparable to the speed of basic-level object categorization, but slower than that of superordinate object categorization. The performance seemed to be crucially mediated by low-level factors, with color leading to a solid increase in performance for material categorization. At longer presentation durations, material categorization was less accurate than both types of object categorization. Taken together, our results show that material categorization can be as fast as basic-level object categorization, but is less accurate.     

Free-ranging dogs assess the quantity of opponents in intergroup conflicts

In conflicts between social groups, the decision of competitors whether to attack/retreat should be based on the assessment of the quantity of individuals in their own and the opposing group. Experimental studies on numerical cognition in animals suggest that they may represent both large and small numbers as noisy mental magnitudes subject to scalar variability, and small numbers (≤4) also as discrete object-files. Consequently, discriminating between large quantities, but not between smaller ones, should become easier as the asymmetry between quantities increases. Here, we tested these hypotheses by recording naturally occurring conflicts in a population of free-ranging dogs, Canis lupus familiaris, living in a suburban environment. The overall probability of at least one pack member approaching opponents aggressively increased with a decreasing ratio of the number of rivals to that of companions. Moreover, the probability that more than half of the pack members withdrew from a conflict increased when this ratio increased. The skill of dogs in correctly assessing relative group size appeared to improve with increasing the asymmetry in size when at least one pack comprised more than four individuals, and appeared affected to a lesser extent by group size asymmetries when dogs had to compare only small numbers. These results provide the first indications that a representation of quantity based on noisy mental magnitudes may be involved in the assessment of opponents in intergroup conflicts and leave open the possibility that an additional, more precise mechanism may operate with small numbers.