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Temporal perception does not always correspond to objective time. Several factors contribute to distort perceived timing of stimuli. This work investigates the effect of repeated stimulus presentation (either a sound or a light) on perceived timing of a subsequent audiovisual pair. At the beginning of each trial, a series of sounds or lights is presented with a constant interval. One final stimulus is presented either rhythmically or with a temporal shift. In a psychophysical task, participants judged whether the last stimulus in the sequence is presented before or after a temporal probe in the other modality. Results indicate two types of effects. First, the last stimulus of the sequence appears to be delayed with respect to the probe in the other modality. Second, deviations from regular rhythm tend to be perceptually compensated. Overall, perceived stimulus timing is shown to be affected by the temporal context, and the effect is consistent with a change in perceptual latency. The change depends on the modality of the repeated stimulus and can be explained as a combined effect of an temporal adaptation (i.e., slowing down perception) plus a temporal expectation acting on the slightly arrhythmic stimuli.

In: Seeing and Perceiving

An isochronous sequence is a series of repeating events with the same inter-onset-interval. A common finding is that as the length of a sequence increases, so does temporal sensitivity to irregularities — that is, the detection of deviations from isochrony is better with a longer sequence. Several theoretical accounts exist in the literature as to how the brain processes sequences for the detection of irregularities, yet there remains to be a systematic comparison of the predictions that such accounts make. To compare the predictions of these accounts, we asked participants to report whether the last stimulus of a regularly-timed sequence appeared ‘earlier’ or ‘later’ than expected. Such task allowed us to separately analyse bias and performance. Sequences lengths (3, 4, 5 or 6 beeps) were either randomly interleaved or presented in separate blocks. We replicate previous findings showing that temporal sensitivity increases with longer sequence in the interleaved condition but not in the blocked condition (where performance is higher overall). Results also indicate that there is a consistent bias in reporting whether the last stimulus is isochronous (irrespectively of how many stimuli the sequence is composed of). Such result is consistent with a perceptual acceleration of stimuli embedded in isochronous sequences. From the comparison of the models’ predictions we determine that the improvement in sensitivity is best captured by an averaging of successive estimates, but with an element that limits performance improvement below statistical optimality. None of the models considered, however, provides an exhaustive explanation for the pattern of results found.

In: Timing & Time Perception
Timing and Time Perception: Procedures, Measures, and Applications is a one-of-a-kind, collective effort to present the most utilized and known methods on timing and time perception. Specifically, it covers methods and analysis on circadian timing, synchrony perception, reaction/response time, time estimation, and alternative methods for clinical/developmental research. The book includes experimental protocols, programming code, and sample results and the content ranges from very introductory to more advanced so as to cover the needs of both junior and senior researchers. We hope that this will be the first step in future efforts to document experimental methods and analysis both in a theoretical and in a practical manner.

Contributors are: Patricia V. Agostino, Rocío Alcalá-Quintana, Fuat Balcı, Karin Bausenhart, Richard Block, Ivana L. Bussi, Carlos S. Caldart, Mariagrazia Capizzi, Xiaoqin Chen, Ángel Correa, Massimiliano Di Luca, Céline Z. Duval, Mark T. Elliott, Dagmar Fraser, David Freestone, Miguel A. García-Pérez, Anne Giersch, Simon Grondin, Nori Jacoby, Florian Klapproth, Franziska Kopp, Maria Kostaki, Laurence Lalanne, Giovanna Mioni, Trevor B. Penney, Patrick E. Poncelet, Patrick Simen, Ryan Stables, Rolf Ulrich, Argiro Vatakis, Dominic Ward, Alan M. Wing, Kieran Yarrow, and Dan Zakay.

A field survey was conducted in a highly degraded barren environment in Sicily in order to investigate herpetofaunal community composition and structure, habitat use (niche breadth and overlap) and relative abundance of a snake predator and two species of lizard prey. The site was chosen because it has a simple community structure and thus there is potentially less ecological complexity to cloud any patterns observed. We found an unexpectedly high overlap in habitat use between the two closely related lizards that might be explained either by a high competition for space or through predator-mediated co-existence i.e. the prevention of the competitive exclusion of one lizard over the other. We also found a strong positive correlation between predator density and tail damage in lizards and we suggest that tail damage is a direct consequence of snake activity (because no other natural predators occur in the area).

Open Access
In: Contributions to Zoology


Long-term ecological studies are important for understanding wild populations’ dynamics and processes and the actual factors that can determine their decline. Here, we report the results of a 28-years-long (1992–2019) monitoring of three distinct populations of a tortoise, Testudo hermanni, in Central Italy, with an emphasis on their population abundance trends and on the eventual variation in their habitat use across years and among the study areas. Samplings were conducted by Visual Encounter Survey (VES) methodology, and using a suite of statistical analyses including correlations and Generalized Linear Models analyses. Our data showed a statistically significant decline in tortoise sightings through time, and concurrently also a variation in habitat use by tortoises. In all the three study areas, we observed a significant increase of tortoise sighting frequency in the habitat type characterized by high (>taller than 200 cm) shrubby and wooded vegetation. Since our analyses revealed no significant change in the habitat type availability by year in each study area, we suggest that T. hermanni was increasingly selecting closed vegetation spots throughout the years. We hypothesize that this observed trend of shift in habitat selection could be due to lowering their body temperatures to prevent overheating. So, the selection of more covered spots would be a thermal ecology adaptive consequence of the ongoing global warming.

In: Animal Biology