A Markerless Pose Estimator Applicable to Limbless Animals.

The analysis of kinematics, locomotion, and spatial tasks relies on the accurate detection of animal positions and pose. Pose and position can be assessed with video analysis programs, the "trackers." Most available trackers represent animals as single points in space (no pose information available) or use markers to build a skeletal representation of pose. Markers are either physical objects attached to the body (white balls, stickers, or paint) or they are defined in silico using recognizable body structures (e.g., joints, limbs, color patterns). Physical markers often cannot be used if the animals are small, lack prominent body structures on which the markers can be placed, or live in environments such as aquatic ones that might detach the marker. Here, we introduce a marker-free pose-estimator (LACE Limbless Animal traCkEr) that builds the pose of the animal de novo from its contour. LACE detects the contour of the animal and derives the body mid-line, building a pseudo-skeleton by defining vertices and edges. By applying LACE to analyse the pose of larval Drosophila melanogaster and adult zebrafish, we illustrate that LACE allows to quantify, for example, genetic alterations of peristaltic movements and gender-specific locomotion patterns that are associated with different body shapes. As illustrated by these examples, LACE provides a versatile method for assessing position, pose and movement patterns, even in animals without limbs.

Cross-Modal Integration of Reward Value during Oculomotor Planning.

Reward value guides goal-directed behavior and modulates early sensory processing. Rewarding stimuli are often multisensory, but it is not known how reward value is combined across sensory modalities. Here we show that the integration of reward value critically depends on whether the distinct sensory inputs are perceived to emanate from the same multisensory object. We systematically manipulated the congruency in monetary reward values and the relative spatial positions of co-occurring auditory and visual stimuli that served as bimodal distractors during an oculomotor task performed by healthy human participants (male and female). The amount of interference induced by the distractors was used as an indicator of their perceptual salience. Our results across two experiments show that when reward value is linked to each modality separately, the value congruence between vision and audition determines the combined salience of the bimodal distractors. However, the reward value of vision wins over the value of audition if the two modalities are perceived to convey conflicting information regarding the spatial position of the bimodal distractors. These results show that in a task that highly relies on the processing of visual spatial information, the reward values from multiple sensory modalities are integrated with each other, each with their respective weights. This weighting depends on the strength of prior beliefs regarding a common source for incoming unisensory signals based on their congruency in reward value and perceived spatial alignment.

Sex difference in attractiveness perceptions of strong and weak male walkers.

OBJECTIVES: Men and women accurately assess male physical strength from facial and body morphology cues. Women's assessments of male facial attractiveness, masculinity, and dominance correlate positively with male physical strength. A positive relationship also has been reported between physical strength and attractiveness of men's dance movements. Here, we investigate men's and women's attractiveness, dominance, and strength assessments from brief samples of male gait. METHODS: Handgrip strength (HGS) was measured in 70 heterosexual men and their gait was motion-captured. Men and women judged 20 precategorized strong (high HGS) and weak (low HGS) walkers on attractiveness, dominance, and strength, and provided a measure of their own HGS. RESULTS: Both men and women judged strong walkers higher on dominance and strength than weak walkers. Women but not men judged strong walkers more attractive than weak walkers. These effects were independent of observers' physical strength. CONCLUSIONS: Male physical strength is conveyed not only through facial and body morphology, but also through body movements. We discuss our findings with reference to studies suggesting that physical strength provides information about male quality in contexts of inter- and intrasexual selection. Am. J. Hum. Biol. 28:913-917, 2016. © 2016Wiley Periodicals, Inc.