Object-based Encoding Research Articles

Object-based encoding constrains storage in visual working memory.

The fundamental unit of visual working memory (WM) has been debated for decades. WM could be object-based, such that capacity is set by the number of individuated objects, or feature-based, such that capacity is determined by the total number of feature values stored. The present work examined whether object- or feature-based models would best explain how multifeature objects (i.e., color/orientation or color/shape) are encoded into visual WM. If maximum capacity is limited by the number of individuated objects, then above-chance performance should be restricted to the same number of items as in a single-feature condition. By contrast, if the capacity is determined by independent storage resources for distinct features-without respect to the objects that contain those features-then successful storage of feature values could be distributed across a larger number of objects than when only a single feature is relevant. We conducted four experiments using a whole-report task in which subjects reported both features from every item in a six-item array. The crucial finding was that above-chance recall-for both single- and multifeatured objects-was restricted to the first three or four responses, while the later responses were best modeled as guesses. Thus, whole-report with multifeature objects reveals a distribution of recalled features that indicates an object-based limit on WM capacity. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Object-based encoding in visual working memory: A critical revisit.

Visual working memory (VWM) is responsible for the temporal retention and manipulation of visual information. It has been suggested that VWM employs an object-based encoding (OBE) manner to extract highly discriminable information from visual perception: Whenever one feature dimension of the objects is selected for entry into VWM, the other task-irrelevant highly discriminable dimension is also extracted into VWM involuntarily. However, the task-irrelevant feature in OBE studies might reflect a high capacity fragile VWM (FVWM) trace that stores maskable sensory representations. To directly compare the VWM storage hypothesis and the FVWM storage hypothesis, we used a unique characteristic of FVWM that the representations in FVWM could be erased by backward masks presented at the original locations of the memory array. We required participants to memorise the orientations of three coloured bars while ignoring their colours, and presented backward masks during the VWM maintenance interval. In four experiments, we consistently observed that the OBE occurs regardless of the presentation of the backward masks, except when even the task-relevant features in VWM were significantly interrupted by immediate backward masks, suggesting that the task-irrelevant features of objects are stored in VWM rather than in FVWM.

To OBE or Not To OBE? Revisiting Object-based Encoding (OBE) in in Visual Working Memory

It has been suggested that visual working memory (VWM) adopts an object-based encoding (OBE) manner to extract perceptual information into VWM. That is, whenever even one feature-dimension is selected for entry into VWM, the others are also extracted automatically. Almost all extant studies revealing OBE were conducted by probing an "irrelevant-change distracting effect", in which a change of stored irrelevant-feature dramatically affects the change detection performance of the target feature. However, the existence of irrelevant feature change may affect the participants' processing manner, leading to a false positive result. In the current study, we conducted a strict examination of OBE in VWM, by keeping the irrelevant feature of the memory item constant while probing whether task-irrelevant feature can guide the early deployment of attention in visual search. In particular, we required the participants to memorize an object's color while ignoring shape. Critically, we inserted a visual search task into the maintenance phase of VWM, and the participants searched for a target line among distractor lines, each embedded within a different object. One object in the search display could match the shape, the color or both dimensions of the memory item, but this object never contained the target line. Relative to a neutral baseline (no match between the memory and the search displays), we found that the search time was significantly prolonged in all the three match conditions. Moreover, this pattern was not modulated by the exposure time of memory array (100 or 1000ms), suggesting that similar to the task-relevant feature color, the task-irrelevant shape was also extracted into VWM, and hence affected the search task in a top-down manner. Therefore, the OBE exists in VWM. Meeting abstract presented at VSS 2016

Object-based Encoding in Visual Working Memory: Evidence from Memory-driven Attentional Capture.

Visual working memory (VWM) adopts a specific manner of object-based encoding (OBE) to extract perceptual information: Whenever one feature-dimension is selected for entry into VWM, the others are also extracted. Currently most studies revealing OBE probed an ‘irrelevant-change distracting effect’, where changes of irrelevant-features dramatically affected the performance of the target feature. However, the existence of irrelevant-feature change may affect participants’ processing manner, leading to a false-positive result. The current study conducted a strict examination of OBE in VWM, by probing whether irrelevant-features guided the deployment of attention in visual search. The participants memorized an object’s colour yet ignored shape and concurrently performed a visual-search task. They searched for a target line among distractor lines, each embedded within a different object. One object in the search display could match the shape, colour, or both dimensions of the memory item, but this object never contained the target line. Relative to a neutral baseline, where there was no match between the memory and search displays, search time was significantly prolonged in all match conditions, regardless of whether the memory item was displayed for 100 or 1000 ms. These results suggest that task-irrelevant shape was extracted into VWM, supporting OBE in VWM.

Prolonged focal attention without binding: Tracking a ball for half a minute without remembering its color

Conventional theories of cognition focus on attention as the primary determinant of working memory contents. However, here we show that about one third of observers could not report the color of a ball that they had just been specifically attending for 5–59s. This counterintuitive result was obtained when observers repeatedly counted the passes of one of two different colored balls among actors in a video and were then unexpectedly asked to report the color of the ball that they had just tracked. Control trials demonstrated that observers’ color report performance increased dramatically once they had an expectation to do so. Critically, most of the incorrect color responses were the distractor ball color, which suggested memory storage without binding. Therefore, these results, together with other recent findings argued against two opposing theories: object-based encoding and feature-based encoding. Instead, we propose a new hypothesis by suggesting that the failure to report color is because participants might only activate the color representation in long-term memory without binding it to object representation in working memory.

Binding biological motion and visual features in working memory.

Working memory mechanisms for binding have been examined extensively in the last decade, yet few studies have explored bindings relating to human biological motion (BM). Human BM is the most salient and biologically significant kinetic information encountered in everyday life and is stored independently from other visual features (e.g., colors). The current study explored 3 critical issues of BM-related binding in working memory: (a) how many BM binding units can be retained in working memory, (b) whether involuntarily object-based binding occurs during BM binding, and (c) whether the maintenance of BM bindings in working memory requires attention above and beyond that needed to maintain the constituent dimensions. We isolated motion signals of human BM from non-BM sources by using point-light displays as to-be-memorized BM and presented the participants colored BM in a change detection task. We found that working memory capacity for BM-color bindings is rather low; only 1 or 2 BM-color bindings could be retained in working memory regardless of the presentation manners (Experiments 1-3). Furthermore, no object-based encoding took place for colored BM stimuli regardless of the processed dimensions (Experiments 4 and 5). Central executive attention contributes to the maintenance of BM-color bindings, yet maintaining BM bindings in working memory did not require more central attention than did maintaining the constituent dimensions in working memory (Experiment 6). Overall, these results suggest that keeping BM bindings in working memory is a fairly resource-demanding process, yet central executive attention does not play a special role in this cross-module binding.

Object-based encoding in visual working memory: A life span study

Recent studies on development of visual working memory (VWM) predominantly focus on VWM capacity and spatial-based information filtering in VWM. Here we explored another new aspect of VWM development: object-based encoding (OBE), which refers to the fact that even if one feature dimension is required to be selected into VWM, the other irrelevant dimensions are also extracted. We explored the OBE in children, young adults, and old adults, by probing an "irrelevant-change distracting effect" in which a change of stored irrelevant feature dramatically affects the performance of task-relevant features in a change-detection task. Participants were required to remember two or four simple colored shapes, while color was used as the relevant dimension. We found that changes to irrelevant shapes led to a significant distracting effect across the three age groups in both load conditions; however, children showed a greater degree of OBE than did young and old adults. These results suggest that OBE exists in VWM over the life span (6-67 years), yet continues to develop along with VWM.

Robust object-based encoding in visual working memory.

Recently, researchers have begun to investigate how nonspatial perceptual information is extracted into visual working memory (VWM), focusing particularly on object-based encoding (OBE). That is, whenever even one feature-dimension is selected for entry into VWM, the others are also extracted automatically. While there is evidence supporting robust OBE in VWM, some researchers have argued that it is restricted to certain conditions, suggesting that OBE might be weak. The current study analyzed the experimental differences between prior studies revealing OBE and the ones that failed, and suggested that there were three critical differences in the experimental settings. Studies supporting robust OBE predominantly were conducted by probing an "irrelevant-change distracting effect," in which a change of stored irrelevant-feature dramatically affects performance. To examine whether OBE in VWM is robust or weak, we manipulated these three aspects under the irrelevant-change distracting effect to check whether OBE could be erased. In three experiments, we found similar degrees of the distracting effect between the experimental condition (controlling these factors) and the control condition; this suggests that these factors do not affect OBE. We conclude that robust OBE exists in VWM.

Induced Roelofs effect in reaching

Event Abstract Back to Event Induced Roelofs effect in reaching Bahareh Taghizadeh1 and Alexander Gail1, 2* 1 German Primate Center, Germany 2 Bernstein Center for Computational Neuroscience, Germany Goal-directed reaching requires accurate localization of the target object. But the localization of visual objects is prone to illusions induced by the visual context. In the induced Roelofs effect (IRE), the position of a task irrelevant visual object induces a shift in the localization of the visual target object. This is true when subjects have to indicate the position of the target object relative to an array of reference positions, e.g. by response keys or by pointing to it with delay. In contrast, when subjects in the same task indicate the position of the target object by pointing to it without instructed delay or by directly reaching towards it with or without delay, no IRE is induced [1]. This discrepancy was taken as evidence for separate visuospatial representations for direct sensorimotor processing compared to spatial cognitive processing [2]. Here we test if an IRE can also be induced for reaching movement towards the target stimulus, which would argue against such strictly separate processing. We asked human subjects to perform reaches towards visual target stimuli in the frontoparallel plane. Each trial started with a brief appearance of a reference array (RA) of five horizontally arranged boxes which indicated the potential target positions. Then the target and a surrounding task-irrelevant visual frame were flashed, followed by a decision array (DA) immediately after the cue/frame offset. The DA was identical to the RA, but could be placed at different positions on the screen. While keeping ocular fixation, subjects had to reach towards the DA box which corresponded to the RA box in which they had seen the flashed target. The results showed a reliable IRE for reaching. In our task the reach goal needed to be defined relative to a task-relevant object, i.e. in an object-based reference frame, while in previous experiments the reach goal was directly defined by the target objects. The results suggest that during object-based encoding of motor goal locations, the information of additional task-irrelevant objects can induce systematic mis-localizations of the reach goal. This finding argues against strictly separate visuospatial representations for direct sensorimotor processing compared to spatial cognitive processing.

Neural fate of unattended features in object-based encoding

Neural fate of unattended features in object-based encoding

P2P Object-based adaptivE Multimedia Streaming (POEMS)

Peer-to-peer (P2P) paradigm has recently gained tremendous attraction and is widely used for content distribution and sharing. The future multimedia communication applications have to support the user's needs, the terminal capabilities, the content specification and the underlying networking technologies. They should be network-aware, topology-aware, and end-user-centric. Thus, in this paper, we use the characteristics of the object-based encoding scheme and P2P network topology to propose adaptive content delivery architecture for P2P networks. We propose an efficient mechanism for transmission of real-time content over P2P networks, called POEMS (P2P Object-based adaptivE Multimedia Streaming). This object-based audio-visual quality adaptive mechanism over P2P networks is media-aware, network-aware, and user-centric that is carried-out through (1) selection of appropriate sending peers willing to participate in the streaming mechanism, (2) organization of sending peers by constructing an overlay network to facilitate content delivery and adaptation, (3) dynamicity management of peers when some peer enters or leaves the system to maintain an acceptable level of perceived video quality, and (4) ensuring the end-to-end QoS (Quality of Services) by orchestrating the overall streaming mechanism. The obtained results demonstrate that combining content adaptation using object-based encoding and advance network-aware peers selection based on peer monitoring leads to intelligent, efficient, and large-scale support of multimedia services over complex network architectures.

A configural effect in visual short-term memory for features from different parts of an object

Previous studies have shown that change detection performance is improved when the visual display holds features (e.g., a colour and an orientation) that are grouped into different parts of the same object compared to when they are all spatially separated (Xu, 2002a, 2002b). These findings indicate that visual short-term memory (VSTM) encoding can be "object based". Recently, however, it has been demonstrated that changing the orientation of an item could affect the spatial configuration of the display (Jiang, Chun, & Olson, 2004), which may have an important influence on change detection. The perceptual grouping of features into an object obviously reduces the amount of distinct spatial relations in a display and hence the complexity of the spatial configuration. In the present study, we ask whether the object-based encoding benefit observed in previous studies may reflect the use of configural coding rather than the outcome of a true object-based effect. The results show that when configural cues are removed, the object-based encoding benefit remains for features (i.e., colour and orientation) from different parts of an object, but is significantly reduced. These findings support the view that memory for features from different parts of an object can benefit from object-based encoding, but the use of configural coding significantly helps enlarge this effect.

Semantic video analysis for adaptive content delivery and automatic description

We present an encoding framework which exploits semantics for video content delivery. The video content is organized based on the idea of main content message. In the work reported in this paper, the main content message is extracted from the video data through semantic video analysis, an application-dependent process that separates relevant information from non relevant information. We use here semantic analysis and the corresponding content annotation under a new perspective: the results of the analysis are exploited for object-based encoders, such as MPEG-4, as well as for frame-based encoders, such as MPEG-1. Moreover, the use of MPEG-7 content descriptors in conjunction with the video is used for improving content visualization for narrow channels and devices with limited capabilities. Finally, we analyze and evaluate the impact of semantic video analysis in video encoding and show that the use of semantic video analysis prior to encoding sensibly reduces the bandwidth requirements compared to traditional encoders not only for an object-based encoder but also for a frame-based encoder.

Low-Complexity MPEG-4 Shape Encoding towards Realtime Object-Based Applications

Although frame-based MPEG-4 video services have been successfully deployed since 2000, MPEG-4 video coding is now facing great competition in becoming a dominant player in the market. Object-based coding is one of the key functionalities of MPEG-4 video coding. Realtime object-based video encoding is also important for multimedia broadcasting for the near future. Object-based video services using MPEG-4 have not yet made a successful debut due to several reasons. One of the critical problems is the coding complexity of object-based video coding over frame-based video coding. Since a video object is described with an arbitrary shape, the bitstream contains not only motion and texture data but also shape data. This has introduced additional complexity to the decoder side as well as to the encoder side. In this paper, we have analyzed the current MPEG-4 video encoding tools and proposed efficient coding technologies that reduce the complexity of the encoder. Using the proposed coding schemes, we have obtained a 56 percent reduction in shape-coding complexity over the MPEG-4 video reference software (Microsoft version, 2000 edition).