Effects of motor congruence on visual working memory

Grounded-cognition theories suggest that memory shares processing resources with perception and action. The motor system could be used to help memorize visual objects. In two experiments, we tested the hypothesis that people use motor affordances to maintain object representations in working memory. Participants performed a working memory task on photographs of manipulable and nonmanipulable objects. The manipulable objects were objects that required either a precision grip (i.e., small items) or a power grip (i.e., large items) to use. A concurrent motor task that could be congruent or incongruent with the manipulable objects caused no difference in working memory performance relative to nonmanipulable objects. Moreover, the precision- or power-grip motor task did not affect memory performance on small and large items differently. These findings suggest that the motor system plays no part in visual working memory.     

Repetition blindness and repetition priming: Effects of featural differences between targets and distractors on RSVP dual-target search

In six experiments, we investigated the influence of featural differences between targets and distractors on the detection and identification of dissimilar and repeated targets in conditions that typically produce an attentional blink and repetition blindness (when a target is repeated). Rapid serial visual presentation streams were presented that contained letter targets and distractors that were either letters or digits. The targets and the distractors were either the same color or a different color and were presented either in the same font or in a differentfont. Dual-target performance on nonrepeat trials was strongly enhanced when the targets were colored. In addition, when subjects used either the color or the font cues to select the targets, there was benefit of repetition on dual-target report, instead of repetition blindness. The results suggest that featural differences between targets and distractors play an important role in registering stimuli as distinct objects.     

Object manipulability affects children’s and adults’ conceptual processing

Research on kinds of concepts indicates that children use perceptual and functional information differently to form natural and artifact concepts. Beyond object domain, object manipulability appears to be a decisive factor in adult conceptual processing. Thus, the effect of object manipulability on conceptual processing was tested in 5- and 7-year-olds and adults using a picture matching task. Reaction times for identifying conceptual relations on the basis of perceptual similarity (e.g., jacket-coat) and contextual/functional information (e.g., jacket-hanger) were analyzed according to object manipulability and domain. Both children and adults were faster to identify contextual/functional relations for manipulable than for nonmanipulable objects. Conversely, they were faster to identify perceptual similarity relations for nonmanipulable than for manipulable objects, particularly for natural concepts. Results reveal an early distinction between concepts of manipulable and nonmanipulable objects. Implications for further research on concept formation and for embodied views of concepts are discussed.     

Motor affordance and its role for visual working memory: evidence from fMRI studies

We examined the role of motor affordances of objects for working memory retention processes. Three experiments are reported in which participants passively viewed pictures of real world objects or had to retain the objects in working memory for a comparison with an S2 stimulus. Brain activation was recorded by means of functional magnetic resonance imaging (fMRI). Retaining information about objects for which hand actions could easily be retrieved (manipulable objects) in working memory activated the hand region of the ventral premotor cortex (PMC) contralateral to the dominant hand. Conversely, nonmanipulable objects activated the left inferior frontal gyrus. This suggests that working memory for objects with motor affordance is based on motor programs associated with their use. An additional study revealed that motor program activation can be modulated by task demands: Holding manipulable objects in working memory for an upcoming motor comparison task was associated with left ventral PMC activation. However, retaining the same objects for a subsequent size comparison task led to activation in posterior brain regions. This suggests that the activation of hand motor programs are under top down control. By this they can flexibly be adapted to various task demands. It is argued that hand motor programs may serve a similar working memory function as speech motor programs for verbalizable working memory contents, and that the premotor system mediates the temporal integration of motor representations with other task-relevant representations in support of goal oriented behavior.     

Repetition blindness for novel objects

When visual stimuli (letters, words or pictures of objects) are presented sequentially at high rates (8–12 items/s), observers have difficulty in detecting and reporting both occurrences of a repeated item: This is repetition blindness. Two experiments investigated the effects of repetition of novel objects, and whether the representations bound to episodic memory tokens that yield repetition blindness are viewpoint dependent or whether they are object centred. Subjects were shown coloured drawings of simple three‐dimensional novel objects, and rate of presentation (Experiment 1) and rotation in depth (Experiment 2) were manipulated. Repetition blindness occurred only at the higher rate (105 ms/item), and was found even for stimuli differing in orientation. We conclude that object‐centred representations are bound to episodic memory tokens, and that these are constructed prior to object recognition operating on novel as well as known objects. These results are contrasted with those found with written materials, and implications for explanations of repetition blindness are considered.     

Repetition blindness and illusory conjunctions: errors in binding visual types with visual tokens.

Repetition blindness (Kanwisher, 1986, 1987) has been defined as the failure to detect or recall repetitions of words presented in rapid serial visual presentation (RSVP). The experiments presented here suggest that repetition blindness (RB) is a more general visual phenomenon, and examine its relationship to feature integration theory (Treisman & Gelade, 1980). Experiment 1 shows RB for letters distributed through space, time, or both. Experiment 2 demonstrates RB for repeated colors in RSVP lists. In Experiments 3 and 4, RB was found for repeated letters and colors in spatial arrays. Experiment 5 provides evidence that the mental representations of discrete objects (called "visual tokens" here) that are necessary to detect visual repetitions (Kanwisher, 1987) are the same as the "object files" (Kahneman & Treisman, 1984) in which visual features are conjoined. In Experiment 6, repetition blindness for the second occurrence of a repeated letter resulted only when the first occurrence was attended to. The overall results suggest that a general dissociation between types and tokens in visual information processing can account for both repetition blindness and illusory conjunctions.     

Aging and posture in the memory of manipulable objects

ABSTRACT

Thirty healthy elderly participants (mean age = 77.3) learned the names of manipulable and nonmanipulable objects while adopting a control posture (hands in front of them) or an interfering posture (holding their hands behind their back). Results on a recall task showed a postural interference (PI) effect, with the interfering posture reducing the memory of manipulable objects, but not of nonmanipulable ones. The effect was similar to the Postural Interference effect previously observed in young adults, although with a lower performance. These results call into question the embodied theory hypothesis that the deterioration of memory in aging is related to the decline of the sensorimotor system.     

Language-based access to gestural components of conceptual knowledge

We report two experiments in which production of articulated hand gestures was used to reveal the nature of gestural knowledge evoked by sentences referring to manipulable objects. Two gesture types were examined: functional gestures (executed when using an object for its intended purpose) and volumetric gestures (used when picking up an object simply to move it). Participants read aloud a sentence that referred to an object but did not mention any form of manual interaction (e.g., Jane forgot the calculator) and were cued after a delay of 300 or 750 ms to produce the functional or volumetric gesture associated with the object, or a gesture that was unrelated to the object. At both cue delays, functional gestures were primed relative to unrelated gestures, but no significant priming was found for volumetric gestures. Our findings elucidate the types of motor representations that are directly linked to the meaning of words referring to manipulable objects in sentences.     

Gesturing and naming: the use of functional knowledge in object identification

Studies using functional imaging show reliable activation of premotor cortex when observers view manipulable objects. This result has led to the view that knowledge of object function, particularly the actions associated with the typical use of objects, may play a causal role in object identification. To obtain relevant evidence regarding this causal role, we asked subjects to learn gesture-color associations and then attempt to identify objects presented in colors denoting functional gestures that were congruent or incongruent with the objects' use. A strong congruency effect was observed when subjects gestured the use of an object, but not when they named an object. We conclude that our procedure constitutes a sensitive measure of the recruitment and causal role of functional knowledge and that this recruitment is not present during object naming. Preliminary evidence, however, indicates that gestures evoked by the volumetric shape of an object do contribute to object naming.     

Is motor knowledge part and parcel of the concepts of manipulable artifacts? Clues from a case of upper limb aplasia

The sensory-motor theory of conceptual representations assumes that motor knowledge of how an artifact is manipulated is constitutive of its conceptual representation. Accordingly, if we assume that the richer the conceptual representation of an object is, the easier that object is identified, manipulable artifacts that are associated with motor knowledge should be identified more accurately and/or faster than manipulable artifacts that are not (everything else being equal). In this study, we tested this prediction by investigating the identification of manipulable artifacts in an individual, DC, who was totally deprived of hand motor experience due to upper limb aplasia. This condition prevents him from interacting with most manipulable artifacts, for which he thus has no motor knowledge at all. However, he had motor knowledge for some of them, which he routinely uses with his feet. We contrasted DC’s performance in a timed picture naming task for manipulable artifacts for which he had motor knowledge versus those for which he had no motor knowledge. No detectable advantage on DC’s naming performance was found for artifacts for which he had motor knowledge compared to those for which he did not. This finding suggests that motor knowledge is not part of the concepts of manipulable artifacts.     

Orientation-invariant object recognition: evidence from repetition blindness

The question of whether object recognition is orientation-invariant or orientation-dependent was investigated using a repetition blindness (RB) paradigm. In RB, the second occurrence of a repeated stimulus is less likely to be reported, compared to the occurrence of a different stimulus, if it occurs within a short time of the first presentation. This failure is usually interpreted as a difficulty in assigning two separate episodic tokens to the same visual type. Thus, RB can provide useful information about which representations are treated as the same by the visual system. Two experiments tested whether RB occurs for repeated objects that were either in identical orientations, or differed by 30, 60, 90, or 180 degrees . Significant RB was found for all orientation differences, consistent with the existence of orientation-invariant object representations. However, under some circumstances, RB was reduced or even eliminated when the repeated object was rotated by 180 degrees , suggesting easier individuation of the repeated objects in this case. A third experiment confirmed that the upside-down orientation is processed more easily than other rotated orientations. The results indicate that, although object identity can be determined independently of orientation, orientation plays an important role in establishing distinct episodic representations of a repeated object, thus enabling one to report them as separate events.     

Is a pre-change object representation weakened under correct detection of a change?

We investigated whether a pre-change representation is inhibited or weakened under correct change detection. Two arrays of six objects were rapidly presented for change detection in three experiments. After detection, the perceptual identification of degraded stimuli was tested in Experiments 1 and 2. The weakening of a pre-change representation was not observed under correct detection. The repetition priming effect was observed for a pre-change object and the magnitude was equivalent to the effect for a post-change object. Under change blindness, repetition priming for a pre-change representation was observed when detection did not require report of location in Experiment 1 and was not observed when location was required to be reported in Experiment 2. The results of Experiment 3 showed that a pre-change representation was recognized at a higher rate under correct detection than under change blindness, reflecting a stronger rather than a weaker pre-change representation in the former context.     

Testing the embodied account of object naming: A concurrent motor task affects naming artifacts and animals

Embodied theories of object representation propose that the same neural networks are involved in encoding and retrieving object knowledge. In the present study, we investigated whether motor programs play a causal role in the retrieval of object names. Participants performed an object-naming task while squeezing a sponge with either their right or left hand. The objects were artifacts (e.g. hammer) or animals (e.g. giraffe) and were presented in an orientation that favored a grasp or not. We hypothesized that, if activation of motor programs is necessary to retrieve object knowledge, then concurrent motor activity would interfere with naming manipulable artifacts but not non-manipulable animals. In Experiment 1, we observed naming interference for all objects oriented towards the occupied hand. In Experiment 2, we presented the objects in more ‘canonical orientations’. Participants named all objects more quickly when they were oriented towards the occupied hand. Together, these interference/facilitation effects suggest that concurrent motor activity affects naming for both categories. These results also suggest that picture-plane orientation interacts with an attentional bias that is elicited by the objects and their relationship to the occupied hand. These results may be more parsimoniously accounted for by a domain-general attentional effect, constraining the embodied theory of object representations. We suggest that researchers should scrutinize attentional accounts of other embodied cognitive effects.     

Spatial Repetition Blindness Is Modulated by Selective Attention to Color or Shape

Subjects reported either the colors or shapes of two simultaneous masked letters. Our first study found that they were less accurate when the reported features were identical ("repetition blindness," or RB), while repetition along the unreported dimension had no effect. Three follow-up studies confirmed that when the same dimension was judged (overtly or covertly) for both stimuli, performance was only affected by repetition along that dimension. However, when different dimensions were judged for the two stimuli, performance was affected by repetition on both dimensions. These findings support new conclusions about both RB and visual attention. First, RB depends critically on visual attention, rather than simply on the stimulus presented or the overt response required. Second, while attention can be restricted to a single visual dimension, this is efficient only when the same dimension is selected for both objects. Selecting the color of one object and the shape of another simultaneous object results in both dimensions being accessed for both objects.     

Motor resources in peripersonal space are intrinsic to spatial encoding: Evidence from motor interference

The aim of this study was to explore the role of motor resources in peripersonal space encoding: are they intrinsic to spatial processes or due to action potentiality of objects? To answer this question, we disentangled the effects of motor resources on object manipulability and spatial processing in peripersonal and extrapersonal spaces. Participants had to localize manipulable and non-manipulable 3-D stimuli presented within peripersonal or extrapersonal spaces of an immersive virtual reality scenario. To assess the contribution of motor resources to the spatial task a motor interference paradigm was used. In Experiment 1, localization judgments were provided with the left hand while the right dominant arm could be free or blocked. Results showed that participants were faster and more accurate in localizing both manipulable and non-manipulable stimuli in peripersonal space with their arms free. On the other hand, in extrapersonal space there was no significant effect of motor interference. Experiment 2 replicated these results by using alternatively both hands to give the response and controlling the possible effect of the orientation of object handles. Overall, the pattern of results suggests that the encoding of peripersonal space involves motor processes per se, and not because of the presence of manipulable stimuli. It is argued that this motor grounding reflects the adaptive need of anticipating what may happen near the body and preparing to react in time.     

SEEING TWO AS ONE:

Abstract -Object tokens are episodic visual representations that mediate the ability to track visual events as they move about and change over time. Multiple tokens also allow the viewer to individuate multiple instances of a single type of object. In the present study, we established a functional link for object tokens in two seemingly disparate visual phenomena: apparent motion and repetition blindness [RB]. In RB, repeated items are more difficult to perceive than unre-peated items. Using displays in which two sets of alphanumeric characters streamed in opposite directions across a computer screen in apparent motion, we found increased RB for targets appearing within a single apparent motion stream, relative to targets in different apparent motion streams. The results are inconsistent with refractory period or memory retrieval accounts of RB and support the role of object tokens in both apparent motion and RB.     

Sound naming in neurodegenerative disease

Modern cognitive neuroscientific theories and empirical evidence suggest that brain structures involved in movement may be related to action-related semantic knowledge. To test this hypothesis, we examined the naming of environmental sounds in patients with corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP), two neurodegenerative diseases associated with cognitive and motor deficits. Subjects were presented with 56 environmental sounds: 28 sounds were of objects that required manipulation when producing the sound, and 28 sounds were of objects that required no manipulation. Subjects were asked to provide the name of the object that produced the sound and also complete a sound-picture matching condition. Subjects included 33 individuals from four groups: CBD/PSP, Alzheimer disease, frontotemporal dementia, and normal controls. We hypothesized that CBD/PSP patients would exhibit impaired naming performance compared with controls, but the impairment would be most apparent when naming sounds associated with actions. We also explored neural correlates of naming environmental sounds using voxel-based morphometry (VBM) of brain MRI. As expected, CBD/PSP patients scored lower on environmental sounds naming (p < 0.007) compared with the controls. In particular, the CBD/PSP patients scored the lowest when naming sounds of manipulable objects (p < 0.05), but did not show deficits in naming sounds of non-manipulable objects. VBM analysis across all groups showed that performance in naming sounds of manipulable objects correlated with atrophy in the left pre-motor region, extending from area six to the middle and superior frontal gyrus. These results indicate an association between impairment in the retrieval of action-related names and the motor system, and suggest that difficulty in naming manipulable sounds may be related to atrophy in the pre-motor cortex. Our results support the hypothesis that retrieval of action-related semantic knowledge involves motor regions in the brain.     

Turning objects on their heads: the influence of the stored axis on object individuation

We used repetition blindness (RB) as a measure of object recognition and compared the pattern of RB obtained for objects with a well-established upright orientation (mono-oriented objects) and those without a usual upright orientation (polyoriented objects), when the critical objects were either in identical orientations or differed by 30 degrees, 60 degrees, 90 degrees, or 180 degrees. Overall, we found robust RB despite differences in orientation, consistent with the idea that object recognition, as indexed by RB, is largely independent of orientation. However, whereas for polyoriented objects RB was obtained in all orientation conditions, for mono-oriented objects there was no RB between upright and upside-down versions of the stimuli. These findings suggest that the usual orientation of an object-when it exists-is stored in memory and can facilitate orientation processing when the principal axis of a viewed object is aligned with the stored axis orientation. This, in turn, allows for more rapid and successful construction of distinct episodic representations of an object, thus alleviating RB.     

Repetition blindness depends on perceptual capture and token individuation failure

A visual prime succeeded by a brief target produces a paradox. Namely, target repetition yields poorer identification accuracy and shorter duration judgments than unrelated prime-target pairs. Experiment 1 manipulated stimulus onset asynchrony to learn when repetition blindness is maximized. Experiments 2 and 3 manipulated expectancy of repetitions through changes in the proportion of repeated trials and instructions, respectively. Results indicate that repetition blindness is influenced by subject strategies and that the change is not mediated by response bias. Experiment 4 showed that increasing the spatial distance between prime and target reduced but did not eliminate repetition blindness. The current data support joint explanation of repetition blindness in terms of perceptual capture (prime-target fusion) and token individuation failure (problems in encoding episodic reoccurrences of an event).