The effect of spatial and nonspatial contextual information on visual object memory

Recent research has found visual object memory can be stored as part of a larger scene representation rather than independently of scene context. The present study examined how spatial and nonspatial contextual information modulate visual object memory. Two experiments tested participants’ visual memory by using a change detection task in which a target object's orientation was either the same as it appeared during initial viewing or changed. In addition, we examined the effect of spatial and nonspatial contextual manipulations on change detection performance. The results revealed that visual object representations can be maintained reliably after viewing arrays of objects. Moreover, change detection performance was significantly higher when either spatial or nonspatial contextual information remained the same in the test image. We concluded that while processing complex visual stimuli such as object arrays, visual object memory can be stored as part of a comprehensive scene representation, and both spatial and nonspatial contextual changes modulate visual memory retrieval and comparison.     

Electrophysiological evidence for colour effects on the naming of colour diagnostic and noncolour diagnostic objects

In this study, we investigated the level of visual processing at which surface colour information improves the naming of colour diagnostic and noncolour diagnostic objects. Continuous electroencephalograms were recorded while participants performed a visual object naming task in which coloured and black-and-white versions of both types of objects were presented. The black-and-white and the colour presentations were compared in two groups of event-related potentials (ERPs): (1) The P1 and N1 components, indexing early visual processing; and (2) the N300 and N400 components, which index late visual processing. A colour effect was observed in the P1 and N1 components, for both colour and noncolour diagnostic objects. In addition, for colour diagnostic objects, a colour effect was observed in the N400 component. These results suggest that colour information is important for the naming of colour and noncolour diagnostic objects at different levels of visual processing. It thus appears that the visual system uses colour information, during naming of both object types, at early visual stages; however, for the colour diagnostic objects naming, colour information is also recruited during the late visual processing stages.     

Independent effects of colour on object identification and memory

We examined the effects of colour on object identification and memory using a study–test priming procedure with a coloured-object decision task at test (i.e., deciding whether an object is correctly coloured). Objects were selected to have a single associated colour and were either correctly or incorrectly coloured. In addition, object shape and colour were either spatially integrated (i.e., colour fell on the object surface) or spatially separated (i.e., colour formed the background to the object). Transforming the colour of an object from study to test (e.g., from a yellow banana to a purple banana) reduced priming of response times, as compared to when the object was untransformed. This utilization of colour information in object memory was not contingent upon colour falling on the object surface or whether the resulting configuration was of a correctly or incorrectly coloured object. In addition, we observed independent effects of colour on response times, whereby coloured-object decisions were more efficient for correctly than for incorrectly coloured objects but only when colour fell on the object surface. These findings provide evidence for two distinct mechanisms of shape–colour binding in object processing.     

Representing object colour in language comprehension

Embodied theories of cognition hold that mentally representing something red engages the neural subsystems that respond to environmental perception of that colour. This paper examines whether implicit perceptual information on object colour is represented during sentence comprehension even though doing so does not necessarily facilitate task performance. After reading a sentence that implied a particular colour for a given object, participants were presented with a picture of the object that either matched or mismatched the implied colour. When asked if the pictured object was mentioned in the preceding sentence, people's responses were faster when the colours mismatched than when they matched, suggesting that object colour is represented differently to other object properties such as shape and orientation. A distinction between stable and unstable embodied representations is proposed to allow embodied theories to account for these findings.     

See an object,hear an object file: Object correspondence transcends sensory modality

An important task of perceptual processing is to parse incoming information into distinct units and to keep track of those units over time as the same, persisting representations. Within the study of visual perception, maintaining such persisting object representations is helped by “object files”—episodic representations that store (and update) information about objects' properties and track objects over time and motion via spatiotemporal information. Although object files are typically discussed as visual, here we demonstrate that object–file correspondence can be computed across sensory modalities. An object file can be initially formed with visual input and later accessed with corresponding auditory information, suggesting that object files may be able to operate at a multimodal level of perceptual processing.     

Establishing object correspondence across eye movements: Flexible use of spatiotemporal and surface feature information

Visual input is frequently disrupted by eye movements, blinks, and occlusion. The visual system must be able to establish correspondence between objects visible before and after a disruption. Current theories hold that correspondence is established solely on the basis of spatiotemporal information, with no contribution from surface features. In five experiments, we tested the relative contributions of spatiotemporal and surface feature information in establishing object correspondence across saccades. Participants generated a saccade to one of two objects, and the objects were shifted during the saccade so that the eyes landed between them, requiring a corrective saccade to fixate the target. To correct gaze to the appropriate object, correspondence must be established between the remembered saccade target and the target visible after the saccade. Target position and surface feature consistency were manipulated. Contrary to existing theories, surface features and spatiotemporal information both contributed to object correspondence, and the relative weighting of the two sources of information was governed by the demands of the task. These data argue against a special role for spatiotemporal information in object correspondence, indicating instead that the visual system can flexibly use multiple sources of relevant information.     

True and false memory for colour names versus actual colours: Support for the visual distinctiveness heuristic in memory for colour information

In a colour variation of the Deese–Roediger–McDermott (DRM) false memory paradigm, participants studied lists of words critically related to a nonstudied colour name (e.g., “blood, cherry, scarlet, rouge … ”); they later showed false memory for the critical colour name (e.g., “red”). Two additional experiments suggest that participants generate colour imagery in response to such colour-related DRM lists. First, participants claim to experience colour imagery more often following colour-related than standard non-colour-related DRM lists; they also rate their colour imagery as more vivid following colour-related lists. Second, participants exhibit facilitative priming for critical colours in a dot selection task that follows words in the colour-related DRM list, suggesting that colour-related DRM lists prime participants for the actual critical colours themselves. Despite these findings, false memory for critical colour names does not extend to the actual colours themselves (font colours). Rather than leading to source confusion about which colours were self-generated and which were studied, presenting the study lists in varied font colours actually worked to reduce false memory overall. Results are interpreted within the framework of the visual distinctiveness hypothesis.     

Infants' emerging ability to represent occluded object motion

The emerging ability to represent an oscillating moving object over occlusions was studied in 7-21-week-old infants. The object moved at 0.25 Hz and was either occluded at the center of the trajectory (for 0.3 s) or at one turning point (for 0.7 s). Each trial lasted for 20 s. Both eye and head movements were measured. By using two kinds of motion, sinusoidal (varying velocity) and triangular (constant velocity), infants' ability to take velocity change into account when predicting the reappearance of the moving object was tested. Over the age period studied, performance at the central occluder progressed from almost total ignorance of what happened to consistent predictive behavior. From around 12 weeks of age, infants began to form representations of the moving object that persisted over temporary occlusions. At around 5 months of age these representations began to incorporate the dynamics of the represented motion. Strong learning effects were obtained over single trials, but there was no evidence of retention between trials. The individual differences were profound.     

The impact of extrafoveal information on visual short-term memory for object position

The role of extrafoveal information in visual short-term memory has been investigated relatively little, and, in most existing studies, using verbalisable stimuli susceptible to the recruitment of long-term memory (LTM). In addition, little is known about the impact of extrafoveal information available pre- and posttarget foveation, as it is typical to provide extrafoveal information prior to the foveation of memory targets. In this study, two object-position recognition experiments were conducted (each with two conditions) to establish the impact of extrafoveal information provided before and after the foveation of memory targets. Stimuli comprised 1/f noise discs that minimised the recruitment of LTM by eliminating verbal and semantic cues. Overall, a greater hit rate was found where extrafoveal information was available; however, performance analyses in which extrafoveal information was considered relative to the temporal lag at which target stimuli were foveated reveals both costs and benefits. A beneficial effect arose only where extrafoveal information was provided after the target had been foveated, but not prior to target foveation. Findings are discussed in terms of recency and extrafoveal perception effects, incorporating a postfoveation object-file refresh mechanism.     

The properties of object representations constructed during visual search in natural scenes

To investigate properties of object representations constructed during a visual search task, we manipulated the proportion of trials/task within a block: In a search-frequent block, 80% of trials were search tasks; remaining trials presented a memory task; in a memory-frequent block, this proportion was reversed. In the search task, participants searched for a toy car (Experiments 1 and 2) or a T-shape object (Experiment 3). In the memory task, participants had to memorize objects in a scene. Memory performance was worse in the search-frequent block than in the memory-frequent block in Experiments 1 and 3, but not in Experiment 2 (token change in Experiment 1; type change in Experiments 2 and 3). Experiment 4 demonstrated that lower performance in the search-frequent block was not due to eye-movement behaviour. Results suggest that object representations constructed during visual search are different from those constructed during memorization and they are modulated by type of target.     

Visual working memory for dynamic objects: Impaired binding between object feature and location

In daily life, people frequently need to observe dynamic objects and temporarily maintain their representations in visual working memory (VWM). The present study explored the mechanism underlying the binding between perceptual features and locations of dynamic objects in VWM. In three experiments, we measured and compared the memory performance for feature-location binding of multiple dynamic and static objects. The results showed that the feature-location binding was impaired for the dynamic objects compared with the static objects. The impairment persisted when the global spatial configuration of the objects remained intact during the motion, as well as when the binding task was relatively easy, such as binding between single-feature objects and coarse locations. The results indicate that object features and locations are not maintained in VWM as well-integrated object files; rather, the formation of feature-location binding may require additional processes, which are disrupted by the constant change of locations in dynamic circumstances. We propose a consolidation process as possible underlying mechanism, and discuss factors that may influence the strength of feature-location binding in dynamic circumstances.     

Use of colour for language processing during reading

The study examined whether literal correspondence is necessary for the use of visual features during word recognition and text comprehension. Eye movements were recorded during reading and used to change the colour of dialogue when it was fixated. In symbolically congruent colour conditions, dialogue of female and male characters was shown in orchid and blue, respectively. The reversed assignment was used in incongruent conditions, and no colouring was applied in a control condition. Analyses of oculomotor activity revealed Stroop-type congruency effects during dialogue reading, with shorter viewing durations in congruent than incongruent conditions. Colour influenced oculomotor measures that index the recognition and integration of words, indicating that it influenced multiple stages of language processing.     

The role of temporal synchrony in perceptual object formation and updating

The appearance and disappearance of an object in the visual field is accompanied by changes to multiple visual features at the object's location. When features at a location change asynchronously, the cue of common onset and offset becomes unreliable, with observers tending to report the most recent pairing of features. Here, we use these last feature reports to study the conditions that lead to a new object representation rather than an update to an existing representation. Experiments 1 and 2 establish that last feature reports predominate in asynchronous displays when feature durations are brief. Experiments 3 and 4 demonstrate that these reports also are critically influenced by whether features can be grouped using nontemporal cues such as common shape or location. The results are interpreted within the object-updating framework (Enns, Lleras, & Moore, 2010), which proposes that human vision is biased to represent a rapid image sequence as one or more objects changing over time.     

Eccentricity biases of object categories are evident in visual working memory

In high-order object areas, face-selective areas prefer centrally presented stimuli, whereas building-selective areas prefer peripherally presented stimuli (Levy et al., 2001). We investigated whether this eccentricity bias was also evident in visual working memory. In Experiment 1, we found that working memory performance for faces decreased towards the periphery while the performance for buildings remained unchanged across different eccentricities. To rule out the possibility that lower level features influence these results, we manipulated the spatial frequency of faces and buildings (Experiment 2) and the spatial layout information of the buildings (Experiment 3). In both of the experiments, we replicated the results of Experiment 1, even when these lower level features of stimuli were controlled. Consistent with previous findings, the current results suggest that each object category is processed in a different manner depending on the eccentricity. This eccentricity bias is likely the result of how the high-order object areas represent different object categories.     

The development of visual short-term memory for multifeature items during middle childhood

Visual short-term memory (VSTM) research suggests that the adult capacity is limited to three or four multifeature object representations. Despite evidence supporting a developmental increase in capacity, it remains unclear what the unit of capacity is in children. The current study employed the change detection paradigm to investigate both the capacity and nature of the representations of VSTM in 7-year-olds, 10-year-olds, and adults. Two experimental conditions were used to compare memory performance for single-feature objects with that for multifeature objects. Results provided further and more convincing evidence for a developmental increase in VSTM. Furthermore, the “loading up” of features in the multifeature condition was found to incur no significant performance deficit in all age groups. These findings are explained in terms of a developmental increase in the number of integrated multifeature object representations in VSTM.     

Attention to distinguishing features in object recognition

This study advances the hypothesis that, in the course of object recognition, attention is directed to distinguishing features: visual information that is diagnostic of object identity in a specific context. In five experiments, observers performed an object categorization task involving drawings of fish (Experiments 1–4) and photographs of natural sea animals (Experiment 5). Allocation of attention to distinguishing and non-distinguishing features was examined using primed-matching (Experiment 1) and visual probe (Experiments 2, 4, 5) methods, and manipulated by spatial precuing (Experiment 3). Converging results indicated that in performing the object categorization task, attention was allocated to the distinguishing features in a context-dependent manner, and that such allocation facilitated performance. Based on the view that object recognition, like categorization, is essentially a process of discrimination between probable alternatives, the implications of the findings for the role of attention to distinguishing features in object recognition are discussed.     

The relationship between object files and conscious perception

Object files (OFs) are hypothesized mid-level representations which mediate our conscious perception of persisting objects-e.g. telling us 'which went where'. Despite the appeal of the OF framework, not previous research has directly explored whether OFs do indeed correspond to conscious percepts. Here we present at least one case wherein conscious percepts of 'which went where' in dynamic ambiguous displays diverge from the analogous correspondence computed by the OF system. Observers viewed a 'bouncing/streaming' display in which two identical objects moved such that they could have either bounced off or streamed past each other. We measured two dependent variables: (1) an explicit report of perceived bouncing or streaming; and (2) an implicit 'object-specific preview benefit' (OSPB), wherein a 'preview' of information on a specific object speeds the recognition of that information at a later point when it appears again on the same object (compared to when it reappears on a different object), beyond display-wide priming. When the displays were manipulated such that observers had a strong bias to perceive streaming (on over 95% of the trials), there was nevertheless a strong OSPB in the opposite direction-such that the object files appeared to have 'bounced' even though the percept 'streamed'. Given that OSPBs have been taken as a hallmark of the operation of object files, the five experiments reported here suggest that in at least some specialized (and perhaps ecologically invalid) cases, conscious percepts of 'which went where' in dynamic ambiguous displays can diverge from the mapping computed by the object-file system.     

Object representations maintain attentional control settings across space and time

Previous research has revealed that we create and maintain mental representations for perceived objects on the basis of their spatiotemporal continuity. An important question is what type of information can be maintained within these so-called object files. We provide evidence that object files retain specific attentional control settings for items presented inside the object, even when it disappears from vision. The objects were entire visual search displays consisting of multiple items moving into and out of view. It was demonstrated that search was speeded when the search target position was repeated from trial to trial, but especially so when spatiotemporal continuity suggested that the entire display was the same object. We conclude that complete spatial attentional biases can be stored in an object file.     

Categorical perception of colour in the left and right visual field is verbally mediated: evidence from Korean

In this study we demonstrate that Korean (but not English) speakers show Categorical perception (CP) on a visual search task for a boundary between two Korean colour categories that is not marked in English. These effects were observed regardless of whether target items were presented to the left or right visual field. Because this boundary is unique to Korean, these results are not consistent with a suggestion made by Drivonikou [Drivonikou, G. V., Kay, P., Regier, T., Ivry, R. B., Gilbert, A. L., Franklin, A. et al. (2007) Further evidence that Whorfian effects are stronger in the right visual field than in the left. Proceedings of the National Academy of Sciences 104, 1097-1102] that CP effects in the left visual field provide evidence for the existence of a set of universal colour categories. Dividing Korean participants into fast and slow responders demonstrated that fast responders show CP only in the right visual field while slow responders show CP in both visual fields. We argue that this finding is consistent with the view that CP in both visual fields is verbally mediated by the left hemisphere language system.