The development of lexical competition in written- and spoken-word competition

Efficient word recognition depends on the ability to overcome competition from overlapping words. The nature of the overlap depends on the input modality: spoken words have temporal overlap from other words that share phonemes in the same positions, whereas written words have spatial overlap from other words with letters in the same places. It is unclear how these differences in input format affect the ability to recognize a word and the types of competitors that become active while doing so. This study investigates word recognition in both modalities in children between 7 and 15. Children complete a visual-world paradigm eye-tracking task that measures competition from words with several types of overlap, using identical word lists between modalities. Results showed correlated developmental changes in the speed of target recognition in both modalities. Additionally, developmental changes were seen in the efficiency of competitor suppression for some competitor types in the spoken modality. These data reveal some developmental continuity in the process of word recognition independent of modality, but also some instances of independence in how competitors are activated. Stimuli, data and analyses from this project are available at: https://osf.io/eav72

Evolving the capacity for socially guided vocal learning in songbirds: a preliminary study

Socially guided vocal learning, the ability to use contingent reactions from social partners to guide immature vocalizations to more mature forms, is thought to be a rare ability known to be used only by humans, marmosets and two unrelated songbird species (brown-headed cowbirds and zebra finches). However, this learning strategy has never been investigated in the vast majority of species that are known to modify their vocalizations over development. We propose a novel, preliminary evolutionary modelling approach that uses ecological, reproductive and developmental traits to predict which species may incorporate social influences as part of their vocal learning system. We demonstrate our model using data from 28 passerines. We found three highly predictive traits: temporal overlap between sensory (memorization) and sensorimotor (practice) phases of song learning, song used for mate attraction, and social gregariousness outside the breeding season. Species with these traits were distributed throughout the clade, suggesting that a trait-based approach may yield new insights into the evolution of learning strategies that cannot be gleaned from phylogenetic relatedness alone. Our model suggests several previously uninvestigated and unexpected species as likely socially guided vocal learners and offers new insight into the evolution and development of vocal learning. This article is part of the theme issue ‘Vocal learning in animals and humans’.

Co-Occurrence of Domestic Dogs and Gastropod Molluscs in Public Dog-Walking Spaces and Implications for Infection with Angiostrongylus vasorum: A Preliminary Study

Angiostrongylusvasorum is a helminth parasite of domestic dogs that is increasing in range and prevalence. Its lifecycle requires terrestrial gastropod mollusc (“gastropod”) intermediate hosts, but research is lacking regarding contact risk in situ. We studied co-occurrence between dogs and gastropods in dog-walking spaces in an A. vasorum hotspot in southern England, United Kingdom, with the aim of quantifying environmental and spatio-temporal overlap. We surveyed 390 quadrats and 180 point-counts along 3 km transects at seven sites, yielding 1672 gastropod and 763 dog observations. Common gastropods comprised Arion, Cornu, Monacha, Deroceras, Tandonia, Cochlicella, and Trochulus species. Habitat was the most important factor structuring both gastropod and dog presence and abundance. Likelihood ratio comparisons from conditional probability trees revealed that dogs were 15× more likely to be present on hardstanding surfaces than other habitats but were also present on natural and amenity grassland. Presence of gastropod species associated with high A. vasorum prevalence was 65.12× more likely in woodland/scrub and 62.17× more likely in amenity grassland than other habitats. For gastropods overall, high abundance was 5.82× more likely in woodland/scrub and natural grassland. The findings suggest co-occurrence is highest in amenity and natural grassland, but infection risk is greatest in amenity grassland and woodland/scrub.

The Overnight Retention of Novel Metaphors Associates With Slow Oscillation–Spindle Coupling but Not With Respiratory Phase at Encoding

Accumulating evidence emphasizes the relevance of oscillatory synchrony in memory consolidation during sleep. Sleep spindles promote memory retention, especially when occurring in the depolarized upstate of slow oscillation (SO). A less studied topic is the inter-spindle synchrony, i.e. the temporal overlap and phasic coherence between spindles perceived in different electroencephalography channels. In this study, we examined how synchrony between SOs and spindles, as well as between simultaneous spindles, is associated with the retention of novel verbal metaphors. Moreover, we combined the encoding of the metaphors with respiratory phase (inhalation/exhalation) with the aim of modulating the strength of memorized items, as previous studies have shown that inhalation entrains neural activity, thereby benefiting memory in a waking condition. In the current study, 27 young adults underwent a two-night mixed-design study with a 12-h delayed memory task during both sleep and waking conditions. As expected, we found better retention over the delay containing sleep, and this outcome was strongly associated with the timing of SO–spindle coupling. However, no associations were observed regarding inter-spindle synchrony or respiratory phase. These findings contribute to a better understanding of the importance of SO–spindle coupling for memory. In contrast, the observed lack of association with inter-spindle synchrony may emphasize the local nature of spindle-related plasticity.

Information theory-based approach towards studying anti-coincidence detection via graded amplitude dendritic action potentials.

In contrast to typical all or none action potential, recent discovery of graded amplitude action potentials in cortical neurons enabled the dendrites to perform XOR computation, previously thought to be performed only at network level. Thus, these special neurons can perform anti-coincidence detection at the dendritic level, but a lot is unanswered about this phenomenon. Can such experimentally observed dendritic action potential generating system transmit information about stimuli having varying degrees of temporal overlap? Can the system add to the repertoire of computations performed at dendritic level by enhancing the information transmission about varying amplitude stimuli? In this information theory-based study done in single compartment and two-compartment dendritic models, it is shown that such a system can indeed transmit information about the temporal overlap of stimuli as well as amplitudes of stimuli even at high input noise levels. First, the calculation of mutual information between single stimulus and response i.e. I(S;R) with varying noise showed that the information about temporally overlapping nature of stimuli is precisely transmitted by such a system. Secondly, the time evolution of mutual information was simulated through data from the system and it positively reinforced the above-mentioned result. Next, varying amplitude input stimuli was provided to the system and calculation of mutual information between two stimuli and one response i.e. I(S1,S2;R) with varying noise levels revealed that such a system optimally transmits the information about stimuli even at high noise levels. Finally, calculation of this information measurement with respect to time in an experiment with constant overlap but varying input amplitude again positively reinforced the result.

Diet and activity pattern of leopard in relation to prey in tropical forest ecosystem

Understanding the predator–prey relationship is essential for implementing effective conservation management practices on threatened species. Leopard is a threatened apex mammalian predator that plays a crucial role in ecosystem functions in India’s tropical forest. We assessed the diet and activity pattern of leopards in relation to their prey using diet analysis and camera trapping data from Similipal Tiger Reserve, eastern India. Our results indicated that leopard prefers medium-sized prey such as wild pig, common langur and barking deer represented 60% of the total biomass consumed collectively. Results of 6413 camera trap night in 187 locations revealed that leopards showed cathemeral activity pattern and exhibited positive co-occurrence pattern and significant spatial and temporal overlap with their main prey, the wild pig. However, leopards showed very low spatial and temporal overlap with the second main prey, the common langur. Leopards avoided humans and showed low spatial and temporal overlap with humans. Our findings reveal that a trade-off might drive leopard activity between consuming prey and avoiding anthropogenic disturbances like human activity.

The Impact of Synchronized Tactile Stimulation on Joint Attention in 11-Month-Old Infants

Infants explore the world through many combinations of sight, sound, smell, taste and touch. A recent theory known as the “intersensory redundancy hypothesis” posits that the temporal overlap of stimulation across different sense modalities drives selective attention in infancy. Social communication typically involves visual, auditory and tactile cues for infants. Although infrequently studied, rhythmic touch is thought to be inherently rewarding; if manipulated within a social context, it may be able to reinforce joint attention. Given that joint attention is fundamental to the development of social communication, this study investigated the convergent effects of visual, auditory and tactile cues on the expression of joint attention in 10 infants between 11 to 12 months of age. The addition of synchronized (but not asynchronous) tactile stimulation to natural communication cues was associated with higher performance on a joint attention measure (i.e. more frequent responses to parental requests). Implications for autism are discussed.

The Impact of Synchronized Tactile Stimulation on Joint Attention in 11-Month-Old Infants

Infants explore the world through many combinations of sight, sound, smell, taste and touch. A recent theory known as the “intersensory redundancy hypothesis” posits that the temporal overlap of stimulation across different sense modalities drives selective attention in infancy. Social communication typically involves visual, auditory and tactile cues for infants. Although infrequently studied, rhythmic touch is thought to be inherently rewarding; if manipulated within a social context, it may be able to reinforce joint attention. Given that joint attention is fundamental to the development of social communication, this study investigated the convergent effects of visual, auditory and tactile cues on the expression of joint attention in 10 infants between 11 to 12 months of age. The addition of synchronized (but not asynchronous) tactile stimulation to natural communication cues was associated with higher performance on a joint attention measure (i.e. more frequent responses to parental requests). Implications for autism are discussed.

Spatiotemporal context modulates encoding and retrieval of overlapping events

Overlap between events can lead to interference due to a tradeoff between encoding the present event and retrieving the past event. Temporal context information -- 'when' something occurred, a defining feature of episodic memory -- can cue retrieval of a past event. However, the influence of temporal overlap, or proximity in time, on the mechanisms of interference are unclear. Here, by identifying brain states using scalp electroencephalography (EEG) from male and female human subjects, we show the extent to which temporal overlap promotes interference and induces retrieval. In this experiment, subjects were explicitly directed to either encode the present event or retrieve a past, overlapping event while perceptual input was held constant. We find that the degree of temporal overlap between events leads to selective interference. Specifically, greater temporal overlap between two events leads to impaired memory for the past event selectively when the top-down goal is to encode the present event. Using pattern classification analyses to measure neural evidence for a retrieval state, we find that greater temporal overlap leads to automatic retrieval of a past event, independent of top-down goals. Critically, the retrieval evidence we observe likely reflects a general retrieval mode, rather than retrieval success or effort. Collectively, our findings provide insight into the role of temporal overlap on interference and memory formation.