ASPECT AND AKTIONSART OF SECONDARY ASPECTUAL VERBS IN SERBIAN

The aim of the paper is to investigate aspectual value of secondary aspectual verb phrase in Serbian in terms of both grammatical and lexical aspect (Aktionsart). The present analysis focuses on two secondary aspectualizers krenuti and stati, which when used as lexical verbs have the opposite meanings related to motion in space, but when they appear as phase construction heads both verbs modify the opening segment of the aspectual event. The central idea of the proposal is that event types in general largely depend on temporal structures which need to be contextualized before they are formally identifiable. In other words, contrary to traditional approaches which define lexical aspect as inherent to verb meaning, we claim that each verb form (or any lexical and/or grammatical form for that matter) has an underlying meaning through which it entertains systematic relations with other forms in a language (Hirtle 1982:40). We start form aspectual and Aktionsart features of krenuti and stati as verb lexemes, then move onto the level of syntax to identify the co-compositional aspect of the overall phase construction via event structure and event segmentation mechanisms. Finally, the present paper aims to examine different uses of the two secondary aspectual verbs, along with the different types of events they can denote in order to bring to light the potential meanings which give rise to the various contextual senses of the aspectual construction. The reported results of the analysis were checked on the Corpus of Contemporary Serbian Language (SrpKor 2013). Key words: aspectual constructions, Aktionsart, aspectual event, temporal structure, secondary aspectualizer, event segmentation, event co-composition

Time changes: Timing contexts support event segmentation in associative memory

We tend to mentally segment a series of events according to perceptual contextual changes, such that items from a shared context are more strongly associated in memory than items from different contexts. It is also known that timing context provides a scaffold to structure experiences in memory, but its role in event segmentation has not been investigated. We adapted a previous paradigm, which was used to investigate event segmentation using visual contexts, to study the effects of changes in timing contexts on event segmentation in associative memory. In two experiments, we presented lists of 36 items in which the interstimulus intervals (ISIs) changed after a series of six items ranging between 0.5 and 4 s in 0.5 s steps. After each list, participants judged which one of two test items were shown first (temporal order judgment) for items that were either drawn from the same context (within an ISI) or from consecutive contexts (across ISIs). Further, participants judged from memory whether the ISI associated to an item lasted longer than a standard interval (2.25 s) that was not previously shown (temporal source memory). Experiment 2 further included a time-item encoding task. Results revealed an effect of timing context changes in temporal order judgments, with faster responses (Experiment 1) or higher accuracy (Experiment 2) when items were drawn from the same context, as opposed to items drawn from across contexts. Further, in both experiments, we found that participants were well able to provide temporal source memory judgments based on recalled durations. Finally, replicated across experiments, we found subjective duration bias, as estimated by psychometric curve fitting parameters of the recalled durations, correlated negatively with within-context temporal order judgments. These findings show that changes in timing context support event segmentation in associative memory.

Narrative event segmentation in the cortical reservoir

Recent research has revealed that during continuous perception of movies or stories, humans display cortical activity patterns that reveal hierarchical segmentation of event structure. Thus, sensory areas like auditory cortex display high frequency segmentation related to the stimulus, while semantic areas like posterior middle cortex display a lower frequency segmentation related to transitions between events. These hierarchical levels of segmentation are associated with different time constants for processing. Likewise, when two groups of participants heard the same sentence in a narrative, preceded by different contexts, neural responses for the groups were initially different and then gradually aligned. The time constant for alignment followed the segmentation hierarchy: sensory cortices aligned most quickly, followed by mid-level regions, while some higher-order cortical regions took more than 10 seconds to align. These hierarchical segmentation phenomena can be considered in the context of processing related to comprehension. In a recently described model of discourse comprehension word meanings are modeled by a language model pre-trained on a billion word corpus. During discourse comprehension, word meanings are continuously integrated in a recurrent cortical network. The model demonstrates novel discourse and inference processing, in part because of two fundamental characteristics: real-world event semantics are represented in the word embeddings, and these are integrated in a reservoir network which has an inherent gradient of functional time constants due to the recurrent connections. Here we demonstrate how this model displays hierarchical narrative event segmentation properties beyond the embeddings alone, or their linear integration. The reservoir produces activation patterns that are segmented by a hidden Markov model (HMM) in a manner that is comparable to that of humans. Context construction displays a continuum of time constants across reservoir neuron subsets, while context forgetting has a fixed time constant across these subsets. Importantly, virtual areas formed by subgroups of reservoir neurons with faster time constants segmented with shorter events, while those with longer time constants preferred longer events. This neurocomputational recurrent neural network simulates narrative event processing as revealed by the fMRI event segmentation algorithm provides a novel explanation of the asymmetry in narrative forgetting and construction. The model extends the characterization of online integration processes in discourse to more extended narrative, and demonstrates how reservoir computing provides a useful model of cortical processing of narrative structure.

Neural event segmentation of continuous experience in human infants

Although sensory input is continuous, we perceive and remember discrete events. Event segmentation has been studied extensively in adults, but little is known about how the youngest minds experience the world. The main impediment to studying event segmentation in infants has been a reliance on explicit parsing tasks that are not possible at this age. fMRI has recently proven successful at measuring adult event segmentation during task-free, naturalistic perception. Applied to infants, this could reveal the nature of their event segmentation, from low-level sensory transients to high-level cognitive boundaries. We collected fMRI data from 25 adults and 25 infants less than one year of age watching the same short movie. Neural events were defined by the stability of voxel activity patterns. In adults, we replicated a hierarchical gradient of event timescales, from shorter events in early visual regions to longer events in later visual and narrative regions. In infants, however, longer events were found throughout the brain, including in a second dataset. Infant event structure fit adult data and vice versa, but adult behavioral boundaries were differently expressed in adult and infant brains. These findings have implications for the nature of infant experience and cognition.