Integration of perceptual information in word access

According to experiential theories of language comprehension, perceptual information plays an essential role when word meanings are accessed. We conducted four experiments to investigate how different types of perceptual information such as colour and shape are combined during word access. One possibility is that the colour and shape of a word's referent are activated independently from one another and are combined in an additive manner. Alternatively, words might activate perceptual representations via a multiplicative integration of colour and shape. Experiment 1 established that participants follow a multiplicative similarity rule when they judge the similarity of schematic pictures to actual fruits and vegetables. In Experiments 2 to 4, participants performed a classification task, a lexical decision task, or a word-naming task on names of fruits and vegetables that were superimposed on a background picture. Responses were facilitated only when both colour and shape of the picture matched the word's referents. Response times were associated negatively with mean similarity ratings and the consistency of these ratings obtained in the first experiment. These results suggest a multiplicative integration of different types of perceptual information during word access.     

The emergence of words: attentional learning in form and meaning

Children improve at word learning during the 2nd year of life—sometimes dramatically. This fact has suggested a change in mechanism, from associative learning to a more referential form of learning. This article presents an associative exemplar-based model that accounts for the improvement without a change in mechanism. It provides a unified account of children's growing abilities to (a) learn a new word given only 1 or a few training trials ("fast mapping"); (b) acquire words that differ only slightly in phonological form; (c) generalize word meanings preferentially along particular dimensions, such as object shape (the "shape bias"); and (d) learn 2nd labels for already-named objects, despite a persisting resistance to doing so ("mutual exclusivity"). The model explains these improvements in terms of increased attention to relevant aspects of form and meaning, which reduces memory interference. The interaction of associations and reference in word learning is discussed.     

Detection of change in shape: an advantage for concavities

Shape representation was studied using a change detection task. Observers viewed two individual shapes in succession, either identical or one a slightly altered version of the other, and reported whether they detected a change. We found a dramatic advantage for concave compared to convex changes of equal magnitude. Observers were more accurate when a concavity along the contour was introduced, or removed, compared to a convexity. This result sheds light on the underlying representation of visual shape, and in particular the central role played by part-boundaries. Moreover, this finding shows how change detection methodology can serve as a useful tool in studying the specific form of visual representations.     

Determination of visual figure and ground in dynamically deforming shapes

Figure/ground assignment - determining which part of the visual image is foreground and which background - is a critical step in early visual analysis, upon which much later processing depends. Previous research on the assignment of figure and ground to opposing sides of a contour has almost exclusively involved static geometric factors - such as convexity, symmetry, and size - in non-moving images. Here, we introduce a new class of cue to figural assignment based on the motion of dynamically deforming contours. Subjects viewing an animated, deforming shape tended to assign figure and ground so that articulating curvature extrema - i.e., "hinging" vertices - had negative (concave) contour curvature. This articulating-concavity bias is present when all known static cues to figure/ground are absent or neutral in each of the individual frames of the animation, and even seems to override a number of well-known static cues when they are in opposition to the motion cue. We propose that the phenomenon reflects the visual system's inbuilt expectations about the way shapes will deform - specifically, that deformations tend to involve rigid parts articulating at concavities.     

What constrains children's learning of novel shape terms?

In this study, 3-year-olds matched on vocabulary score were taught three new shape terms by one of three types of linguistic contrast: corrective, semantic, or referential. A 5-week training paradigm implemented four training sessions and four assessment sessions. Corrective contrast ("This is concave, it is not square," where square is the child's label for the target) produced more learning than did either semantic or referential contrast. In addition, regardless of group, more was learned about those targets that were classified more variably at pretest. Avoidance of lexical overlap (i.e., using more than one term for the same dimension) might make it more difficult for children to learn new dimensional adjectives, and a "shape bias" might make learning shape terms easier. However, children's expectations about the speaker's communicative intent interacted with the potential benefits of contrast in the semantic condition, and children in that group learned no more than did controls.     

Are summary statistics enough? Evidence for the importance of shape in guiding visual search

Peripheral vision outside the focus of attention may rely on summary statistics. We used a gaze-contingent paradigm to directly test this assumption by asking whether search performance differed between targets and statistically-matched visualizations of the same targets. Four-object search displays included one statistically-matched object that was replaced by an unaltered version of the object during the first eye movement. Targets were designated by previews, which were never altered. Two types of statistically-matched objects were tested: One that maintained global shape and one that did not. Differences in guidance were found between targets and statistically-matched objects when shape was not preserved, suggesting that they were not informationally equivalent. Responses were also slower after target fixation when shape was not preserved, suggesting an extrafoveal processing of the target that again used shape information. We conclude that summary statistics must include some global shape information to approximate the peripheral information used during search.     

Curious Objects: How Visual Complexity Guides Attention and Engagement

Some things look more complex than others. For example, a crenulate and richly organized leaf may seem more complex than a plain stone. What is the nature of this experience—and why do we have it in the first place? Here, we explore how object complexity serves as an efficiently extracted visual signal that the object merits further exploration. We algorithmically generated a library of geometric shapes and determined their complexity by computing the cumulative surprisal of their internal skeletons—essentially quantifying the “amount of information” within each shape—and then used this approach to ask new questions about the perception of complexity. Experiments 1–3 asked what kind of mental process extracts visual complexity: a slow, deliberate, reflective process (as when we decide that an object is expensive or popular) or a fast, effortless, and automatic process (as when we see that an object is big or blue)? We placed simple and complex objects in visual search arrays and discovered that complex objects were easier to find among simple distractors than simple objects are among complex distractors—a classic search asymmetry indicating that complexity is prioritized in visual processing. Next, we explored the function of complexity: Why do we represent object complexity in the first place? Experiments 4–5 asked subjects to study serially presented objects in a self-paced manner (for a later memory test); subjects dwelled longer on complex objects than simple objects—even when object shape was completely task-irrelevant—suggesting a connection between visual complexity and exploratory engagement. Finally, Experiment 6 connected these implicit measures of complexity to explicit judgments. Collectively, these findings suggest that visual complexity is extracted efficiently and automatically, and even arouses a kind of “perceptual curiosity” about objects that encourages subsequent attentional engagement.     

In situ stress relaxation mechanism of a superelastic NiTi shape memory alloy under hydrogen charging

On account of its good biocompatibility, superelastic Ni–Ti arc wire alloys have been successfully used in orthodontic clinics. Nevertheless, delayed fracture in the oral cavity caused by hydrogen diffusion can be observed. The in situ stress relaxation susceptibility of a Ni–Ti shape memory alloy towards hydrogen embrittlement has been examined with respect to the current densities and imposed deformations. Orthodontic wires have been relaxed at different martensite volume fractions using current densities of 5, 10 and 20 A/m² at 20 °C. The in situ relaxation stress shows that, for an imposed strain at the middle of the austenite–martensite transformation, the specimen fractures at the martensite–austenite reverse transformation. However, for an imposed strain at the beginning of the austenite–martensite plateau, the stress decreases in a similar way to the full austenite structure. Moreover, the stress plateau has been recorded at the reverse transformation for a short period. For the fully martensite structure, embrittlement occurs at a higher stress value. This behaviour is attributed to the interaction between the in situ austenite phase expansion and the diffusion of hydrogen in the different volume fractions of the martensite phase, produced at an imposed strain.     

Conscious Vision for Action Versus Unconscious Vision for Action?

David Milner and Melvyn Goodale’s dissociation hypothesis is commonly taken to state that there are two functionally specialized cortical streams of visual processing originating in striate (V1) cortex: a dorsal, action‐related “unconscious” stream and a ventral, perception‐related “conscious” stream. As Milner and Goodale acknowledge, findings from blindsight studies suggest a more sophisticated picture that replaces the distinction between unconscious vision for action and conscious vision for perception with a tripartite division between unconscious vision for action, conscious vision for perception, and unconscious vision for perception. The combination excluded by the tripartite division is the possibility of conscious vision for action. But are there good grounds for concluding that there is no conscious vision for action? There is now overwhelming evidence that illusions and perceived size can have a significant effect on action ( Bruno & Franz, 2009 ; Dassonville & Bala, 2004 ; Franz & Gegenfurtner, 2008 ; McIntosh & Lashley, 2008 ). There is also suggestive evidence that any sophisticated visual behavior requires collaboration between the two visual streams at every stage of the process ( Schenk & McIntosh, 2010 ). I nonetheless want to make a case for the tripartite division between unconscious vision for action, conscious vision for perception, and unconscious vision for perception. My aim here is not to refute the evidence showing that conscious vision can affect action but rather to argue (a) that we cannot gain cognitive access to action‐guiding dorsal stream representations, and (b) that these representations do not correlate with phenomenal consciousness. This vindicates the semi‐conservative view that the dissociation hypothesis is best understood as a tripartite division.     

Developmental differences in shape processing

Considerable evidence indicates that shape similarity plays a major role in object recognition, identification and categorization. However, little is known about shape processing and its development. Across four experiments, we addressed two related questions. First, what makes objects similar in shape? Second, how does the processing of shape similarity develop? We specifically asked whether children and adults determine shape similarity by using categories (e.g., straight vs. curved), as proposed by Biederman (1987), or whether they treat all shape variability uniformly, as proposed by Ullman (1998). Findings from Experiments 1 and 2 suggest that adults and 7-year-olds generally engage in a process in which they impose categories on shape variation and judge objects that fall within those categories as being similar in shape. Four-year-olds are far less likely to engage in such a process. Experiments 3 and 4 address whether 4-year-olds are more likely to treat shape similarity categorically (as older children and adults do) when the objects are given familiar names, functions, and internal properties. Naming did lead to more advanced treatment of shape similarity in some cases. Overall, these findings provide evidence of developmental differences in shape processing and suggest that knowledge of abstract properties of objects may affect the calculation of shape similarity.