Mating behaviour of the lizard Ameiva ameiva in Brazil

The courtship and copulation behaviours of the lizard Ameiva ameiva is described from field observations made at various locations in Brazil. In males, the main behaviours observed during one observation of courtship were head bobbing, circling and walking over the females, rubbing his body against the female, mounting, and dismounting. Females generally remain passive throughout courtship. The reproductive behaviour of A. ameiva resembles that of other teiids, however males exhibit some behavioural peculiarities, such as circling the female to restrict her movements, no cloacal rubbing against the ground, and no biting during copulation.

Beat perception in polyrhythms: Time is structured in binary units

In everyday life, we group and subdivide time to understand the sensory environment surrounding us. Organizing time in units, such as diurnal rhythms, phrases, and beat patterns, is fundamental to behavior, speech, and music. When listening to music, our perceptual system extracts and nests rhythmic regularities to create a hierarchical metrical structure that enables us to predict the timing of the next events. Foot tapping and head bobbing to musical rhythms are observable evidence of this process. In the special case of polyrhythms, at least two metrical structures compete to become the reference for these temporal regularities, rendering several possible beats with which we can synchronize our movements. While there is general agreement that tempo, pitch, and loudness influence beat perception in polyrhythms, we focused on the yet neglected influence of beat subdivisions, i.e., the least common denominator of a polyrhythm ratio. In three online experiments, 300 participants listened to a range of polyrhythms and tapped their index fingers in time with the perceived beat. The polyrhythms consisted of two simultaneously presented isochronous pulse trains with different ratios (2:3, 2:5, 3:4, 3:5, 4:5, 5:6) and different tempi. For ratios 2:3 and 3:4, we additionally manipulated the pitch of the pulse trains. Results showed a highly robust influence of subdivision grouping on beat perception. This was manifested as a propensity towards beats that are subdivided into two or four equally spaced units, as opposed to beats with three or more complex groupings of subdivisions. Additionally, lower pitched pulse trains were more often perceived as the beat. Our findings suggest that subdivisions, not beats, are the basic unit of beat perception, and that the principle underlying the binary grouping of subdivisions reflects a propensity towards simplicity. This preference for simple grouping is widely applicable to human perception and cognition of time.

Beat Perception in Polyrhythms: Time is Structured in Binary Units

In everyday life, we group and subdivide time to understand the sensory environment surrounding us. Our perceptual system establishes hierarchical structures by nesting different groups of time intervals. Organizing time in units such as diurnal rhythms, phrases, and beat patterns, is fundamental to everyday behavior, speech, and music. When listening to music, we extract rhythmic regularities to create a hierarchical metrical structure that enables us to predict the timing of the next events. Foot tapping and head bobbing to musical rhythms are observable evidence of this process. In the special case of polyrhythms, at least two metrical structures compete to become the reference for these temporal regularities, rendering several possible beats with which we can synchronize our movements. While there is general agreement that tempo, pitch, and loudness influence beat perception in polyrhythms, we focused on the yet neglected influence of beat subdivisions. In three online experiments, 300 participants listened to a range of polyrhythms and tapped their index fingers in time with the perceived beat. The polyrhythms consisted of two simultaneously presented isochronous pulse trains with different ratios (2:3, 2:5, 3:4, 3:5, 4:5, 5:6) and different tempi. For ratios 2:3 and 3:4, we additionally manipulated the pitch of the pulse trains. Results showed a highly robust influence of subdivision grouping on beat perception manifested as a propensity towards beats that are subdivided into two or four equally spaced units, as opposed to beats with three or more complex groupings of subdivisions. Additionally, lower pitched pulse trains were more likely to be perceived as the beat. Our findings suggest that subdivisions, not beats, are the basic unit of beat perception, and that the principle underlying the binary grouping of subdivisions reflects a propensity towards simplicity. This preference for simple grouping is widely applicable to human perception and cognition of time.

Introductory gestures before songbird vocal displays are shaped by learning and biological predispositions

Numerous animal displays begin with introductory gestures. For example, lizards start their head-bobbing displays with introductory push-ups, and many songbirds begin their vocal displays by repeating introductory notes (INs) before producing their learned song. Among songbirds, the acoustic structure and the number of INs produced before song vary considerably between individuals in a species. While similar variation in songs between individuals is a result of learning, whether variations in INs are also due to learning remains poorly understood. Here, using natural and experimental tutoring with male zebra finches, we show that mean IN number and IN acoustic structure are learned from a tutor. Interestingly, IN properties and how well INs were learned, were not correlated with the accuracy of song imitation and only weakly correlated with some features of songs that followed. Finally, birds artificially tutored with songs lacking INs still repeated vocalizations that resembled INs, before their songs, suggesting biological predispositions in IN production. These results demonstrate that INs, just like song elements, are shaped both by learning and biological predispositions. More generally, our results suggest mechanisms for generating variation in introductory gestures between individuals while still maintaining the species-specific structure of complex displays like birdsong.

Nocturnal visual displays and call description of the cascade specialist glassfrog Sachatamia orejuela

Although most male frogs call to attract females, vocalizations alone can be ineffective long-range signals in certain environments. To increase conspicuousness and counter the background noise generated by rushing water, a few frog species around the world have evolved visual communication modalities in addition to advertisement calls. These species belong to different families on different continents: a clear example of behavioural convergent evolution. Until now, long-distance visual signalling has not been recorded for any species in the glassfrog family (Centrolenidae). Sachatamia orejuela, an exceptionally camouflaged glassfrog species found within the spray zone of waterfalls, has remained poorly studied. Here, we document its advertisement call for the first time — the frequency of which is higher than perhaps any other glassfrog species, likely an evolutionary response to its disruptive acoustic space — as well as a sequence of non-antagonistic visual signals (foot-flagging, hand-waving, and head-bobbing) that we observed at night.

I walk, therefore I am: a multidimensional study on the influence of the locomotion method upon presence in virtual reality

A defining virtual reality (VR) metric is the sense of presence, a complex, multidimensional psychophysical construct that represents how intense is the sensation of actually being there, inside the virtual environment (VE), forgetting how technology mediates the experience. Our paper explores how locomotion influences presence, studying two different ways of artificial movement along the VE: walking-in-place (through head bobbing detection) and indirect walking (through touchpad). To evaluate that influence, a narrative-neutral maze was created, from where 41 participants (N=41) had to escape. Measuring presence is a controversial topic since there is not a single, objective measure but a wide range of metrics depending on the different theoretical basis. For this reason, we have used for the first time, representative metrics from all three traditional dimensions of presence: subjective presence (SP) (self-reported through questionnaires), behavioral presence (BP) (obtained from unconscious reactions while inside the VE), and physiological presence (PP) [usually measured using heart rate or electrodermal activity (EDA)]. SP was measured with the ITC-SOPI questionnaire, BP by collecting the participants’ reactions, and PP by using a bracelet that registered EDA. The results show two main findings: (i) There is no correlation between the different presence metrics. This opens the door to a simpler way of measuring presence in an objective, reliable way. (ii) There is no significant difference between the two locomotion techniques for any of the three metrics, which shows that the authenticity of VR does not rely on how you move within the VE.

Introductory gestures before songbird vocal displays are shaped by learning and biological predispositions

ABSTRACTIntroductory gestures are present at the beginning of many animal displays. For example, lizards start their head-bobbing displays with introductory push-ups and animal vocal displays begin with introductory notes. Songbirds also begin their vocal displays by repeating introductory notes (INs) before producing their learned song and these INs are thought to reflect motor preparation. Between individuals of a given species, the acoustic structure of INs and the number of times INs are repeated before song varies considerably. While similar variation in songs between individuals is known to be a result of learning, whether INs are also learned remains poorly understood. Here, using natural and experimental tutoring with male zebra finches, we show that mean IN number and IN acoustic structure are learned from a tutor, independent of song learning. We also reveal biological predispositions in IN production; birds artificially tutored with songs lacking INs still repeated a short-duration syllable, thrice on average, before their songs. Overall, these results show that INs, just like elements in song, are shaped both by learning and biological predispositions and suggest multiple, independent, learning processes underlying the acquisition of complex vocal displays.

Immediate Release of Vitreomacular Traction After Pneumatic Vitreolysis Followed by the Drinking Bird Technique

Purpose: To report a case of release of vitreomacular traction (VMT) in a patient with a full thickness macular hole (FTMH) immediately following pneumatic vitreolysis (PV) combined with head bobbing movements. Methods: A 71-year-old female with VMT and an FTMH presented with blurred vision for 2 months to the level of 20/400. At her 1-month follow-up visit, PV was performed using C3F8 gas and she was instructed to perform the drinking bird technique for ten minutes. Results: Optical coherence tomography performed ten minutes after PV with head bobbing showed VMT release and a smaller FTMH. Visual acuity improved to 20/150 immediately afterwards and to 20/80 two months later. Conclusions: Using the drinking bird technique for a continuous period of time immediately following PV may encourage rapid VMT release. PV may be a feasible option for patients with VMT and FTMH who do not want surgery.