Hemispheric asymmetries in phonological processing.

In Serbo-Croat, lexical decision to phonologically bivalent letter strings is slowed relative to their phonologically unique counterparts. This feature was exploited in order to assess the linguistic capacity of the two hemispheres. Lexical decision to laterally presented words and pseudowords revealed a right visual field advantage for both males and females in words and pseudowords. But the demands of phonological processing were not met in the same way by the two hemispheres, the two hemispheres did not respond in the same way in the two sexes, and the pattern of these differences was opposite for words and pseudowords.

Eigenvalues of the inertia tensor and exteroception by the "muscular sense".

Muscle spindles and Golgi tendon organs constitute the receptor foundation to the "muscle sense." Muscle sensitivity has long been assumed relevant to the non-visual perception of the positions and motions of the body's segments and of the properties of hand-held objects. Dynamic touch is the label given to the particular kind of tactile exteroperception that involves a non-spatial input from muscles and tendons. When a hand-held object is wielded, hefted, carried and so on, the hand movements, together with the physical properties of the object, produce torques and angular motions that change in time with the movement. There is, however, an unchanging quantity that relates the variable torques and angular motions, namely, the object's inertia for rotation about a fixed point in the wrist. Our research revealed that the non-visual perception of the length of a wielded object by dynamic touch is a function of muscular sensitivity to the principal moments or eigenvalues of the inertia tensor. Across four experiments, variations in object length were accompanied by variations in width, spatial and material heterogeneity, the relation of the tensorial components to mass, and geometric shape. Subjects had no foreknowledge of the variations in object dimensions. Perceived lengths of occluded objects were reported by adjusting a visible marker so that its position corresponded to the position of the felt end of the object. In each experiment, perceived length was closely related to actual length and uniquely constrained by the major and minor eigenvalues of the inertia tensor. The present results, in conjunction with previous research, suggest that the inertia tensor provides the domains for two sets of functions realized by the "muscular sense," one consisting of the principal moments of inertia or eigenvalues, which map on to perceived object magnitudes (e.g. length, weight), and one consisting of the principal directions or eigenvectors, which map on to perceived relations between hand and object (e.g. position of grasp). The significance of information-perception specificity over cognitive mechanisms is underlined and perspectives on dynamic touch and its underlying muscular sensitivity, including a general tensorial analysis, are discussed.

Affordance, proper function, and the physical basis of perceived heaviness.

The physical basis of perceived heaviness requires consideration of the haptic perceptual system's role in controlling actions (the system's proper function) and the relation of an object's inertial properties to properties of the human movement system (the object's affordance). We show that the mass of a wielded object and particular scalar variables calculated from the object's inertia tensor combine linearly in determining perceived heaviness. The tensor-derived scalars reflect the symmetry and volume of the corresponding inertia ellipsoid. These measures bear directly on the object's wieldability, that is, on the patterning and level of muscular forces required to move the object in a controlled fashion.

When nonwords activate semantics better than words.

We conducted a strong test of the idea that visual word processing and the activation of a printed word's meaning proceeds at a rate scaled by the temporal evolution of a unique and stable phonological code. Using the lexical decision task, and readers fluent in the two alphabets of Serbo-Croatian, we compared the priming of a target word such as automat by the semantically related word ROBOT and by the nonword ROBOT. Whereas the Serbo-Croatian word ROBOT can support two phonological codes, /robot/ and /rovot/, the nonword ROBOT composed by illegally mixing Roman and Cyrillic letters can support only the phonological code /robot/, that corresponding to the word whose meaning is related to automat's. At a prime duration of 35 ms, the lexical decision on the target automat was facilitated by ROBOT but not by ROBOT. At a prime duration of 125 ms, the word ROBOT was the more effective prime. One consequence of phonology's leading role in visual word recognition is that a nonword can sometimes activate a given word's meaning better than the word itself.

Optical information about the severity of upcoming contacts.

The time derivative (tau) of the inverse of the relative rate of optical expansion (tau) may have critical values with potential implications for controlling activity. The present research addresses the particular hypothesis that tau < -0.5 specifies "unsafe" collision courses and tau > or = -0.5 specifies "safe" collision courses. Optical expansion patterns were simulated on a computer with -1.0 < or = tau < 0 and judged as suggesting a "hard" or "soft" collision. tau < -0.5 led to significantly different decisions from tau > or = -0.5, but the critical value of -0.5 was not perceived reliably as soft, a deviation possibly due to discretely approximating continuous functions. Additional experiments evaluated terminal rates of change and display duration and examined the effects of biasing the presented displays toward the soft or the hard end of the tau continuum. The results were consistent with the tau hypothesis.

Dynamical constraints on pictorial action lines.

Pictorial action lines are an effective way of portraying movement in a static drawing. When such lines emanate from the backs of characters, they can give a sense of the path or style of movement. Seven experiments assessed whether photographic streak lines-lines that depict actual movement paths-can, in and of themselves, be informative about the act that produced them. Lines were produced as a darkly clad actor with point-lights attached to his major joints performed a number of actions in front of an open-lens camera. Completely naive Ss had little success identifying events in these photographs. Once Ss were told of the photographic technique, however, striking proficiency was achieved. Subtle distinctions (e.g., whether the movement was forward or backward or performed while wearing weights) were made for some of the events. Results are discussed in terms of various treatments of pictorial information.

Perceptual independence of whole length, partial length, and hand position in wielding a rod.

Previous investigations of dynamic touch have shown that, in wielding an occluded rod, the nonvisible perceptions of total rod length, hand position, and fractional rod length above or below the hand are different functions of the eigenvalues and eigenvectors of the inertia tensor. The implication that the 3 perceptions are independent covariants of the inertia tensor of a wielded object was tested with the complete identification experimental procedure using the statistical prescriptions of F. G. Ashby and J. T. Townsend (1986). The confirmed independence is discussed in the context of the generalized psychological or perception-information hypothesis.

Phase transitions and critical fluctuations in the visual coordination of rhythmic movements between people.

By watching each other's lower oscillating leg, 2 seated Ss kept a common tempo and a particular phase relation of either 0 degrees (symmetric mode) or 180 degrees (alternate mode). This study investigated the differential stability of the 2 phase modes. In Experiment 1, in which Ss were instructed to remain in the initial phase mode, the alternate phase mode was found to be less stable as the frequency of oscillation increased. In addition, analysis of the nonsteady state cycles revealed evidence of a switching to the symmetric phase mode for the initial alternate phase mode trials. In Experiments 2 and 3, Ss were instructed to remain at a noninitial phase angle if it was found to be more comfortable. The transition observed between the 2 phase modes satisfies the criteria of a physical bifurcation--hysteresis, critical fluctuations, and divergence--and is consonant with previous findings on transitions in limb coordination within a person.

Lexical involvement in naming does not contravene prelexical phonology: comment on Sebastián-Gallés (1991).

N. Sebastián-Gallés (1991) showed lexical involvement in naming Spanish. Her results were purported to be a failure to substantiate claims for prelexical phonology that characterize Serbo-Croatian. Summaries of several experimental demonstrations of lexical involvement in naming Serbo-Croatian are used to show that such results are only interpretable consistently in a model that assumes prelexical phonology. The lexicon is accessed through assembled phonology, but assembled and lexical phonology interact in resolving a unique pronunciation when several pronunciations are assembled and in assigning stress, which is not assembled. The authors argue that lexical access need not be different in different orthographies but that the weights on connections between orthographic and phonological substructures established through covariant learning will distinguish orthographies in the rate and degree of phonological involvement in word recognition.

Inertia tensor and weight-percept models of length perception by static holding.

S. J. Lederman, S. R. Ganeshan, and R. E. Ellis (1996) reported an experiment demonstrating that for occluded rods of equal mass and length but different diameters length perception by static holding was larger for rods of smaller diameter. They concluded that participants inferred length from illusory weight percepts. However, rods of equal mass and length that differ in diameter also differ in the eigenvalues of their respective inertia tensors. In the present experiments, the authors manipulated the diameters (Experiment 1) and the inertial eigenvalues (Experiments 4 and 5) of statically held objects. As has been shown with wielded objects, perceived length was a function of the eigenvalues. Additional experiments failed to confirm the expectation from the weight-percept model that perceived length maps to the estimated weight (Experiments 2 and 3). Physical quantities, not psychological quantities, seem to explain length perception by static holding.

Perceiving the width and height of a hand-held object by dynamic touch.

The haptic perceptual sybsystem of dynamic touch is prominent in manipulating and transporting objects, providing a nonvisible awareness of their linear dimensions. The hypothesis that perceptions of object width and height by dynamic touch are different functions of the inertia tensor is addressed. In two experiments heights and widths of nonvisible wielded objects were judged separately. Experiment 1 used solid rectangular parallelepipeds of different sizes; Experiment 2 used objects of identical mass and linear dimensions but nonidentical inertia ellipsoids. Width and height perceptions of comparable reliability and accuracy were found to vary as distinct functions of the objects' inertial eigenvalues. Discussion focused on the notion of tangible shape and on the selectivity of attention within dynamic touch.

Reduction in alphabet priming with delay and degradation.

Phonologically ambiguous Serbo-Croatian words are named more slowly than their phonologically unique partners. This difference is reduced by nonword primes containing consonants unique to one or the other alphabet. In 2 experiments we investigated the hypothesis that alphabet priming is the inhibition of unique and ambiguous letter units of one alphabet by the unique letter units of the other alphabet. In Experiment 1, ambiguous and unique words followed alphabet-specific nonwords at lags between 100 ms and 1,550 ms. The ambiguous-unique difference increased from 1 ms to 45 ms, consistent with a relaxing inhibitory process. In Experiment 2 we compared priming of ambiguous words with and without visual noise. Priming was less for noisy than for intact stimuli, as would be expected if noise slows processing and if the inhibition responsible for priming weakens further during the additional processing time.

Nonvisible perception of segments of a hand-held object and the attitude spinor.

When a rod is grasped at a place intermediate between its ends, the nonvisible perception of length by wielding can be directed to either side of the hand. The selective perception of the lengths of rod segments relative to the hand is hypothesized to depend jointly on the rod's inertia tensor about a fixed rotation point and on the 2-valued attitude spinor connecting the rod's reference frame to the hand's. That hypothesis was tested in 3 experiments m which 8-10 subjects participated; asymmetry in the rod's mass distribution relative to the hand was induced either by the addition of a metal ring to one end or by grasping the rod at a place other than its midpoint. Planes of wielding, style of wielding, and object size were varied across the experiments. The results conformed to expectation: For a given asymmetric rod configuration, perceived length for attending to one direction from the hand (e g., above or left) differed from perceived length for attending to the other direction (below or right); for a given segment of an asymmetric rod, perception of its length did not differ as a function of us direction from the hand. In each experiment, variance in perceived partial length was accommodated by the rod's major eigenvalue and the spinor rotation angle, with rotation sense dictated by the direction of attention.

Low-constraint facilitation in lexical decision with single-word contexts.

Single-word, low-constraint adjective contexts were used to "prime" lexical decision to noun targets in Serbo-Croat. Semantically congruent situations consisted of adjective-noun pairs that were not highly predictable but were nonetheless plausible (e.g., GOOD-AUNT). Semantically incongruent situations used pairs that were implausible (e.g., SLOW-COAT). All adjective-noun pairs were grammatically congruent and were compared with a neutral XXX baseline. In Experiment 1, at a stimulus onset asynchrony of 300 ms, congruous situations showed 59 ms of facilitation while incongruous situations did not differ from the baseline. The same pattern was repeated in Experiment 2, at a stimulus onset asynchrony of 800 ms. Congruous situations were facilitated 67 ms. Results are discussed in terms of a message-level coherence check in Forster's (1979) model of autonomous levels of language processing.

Phonemic, associative, and grammatical context effects with identified and unidentified primes.

Six experiments are reported that assess priming effects on lexical decision (in Serbo-Croatian) when the context is identifiable (unmasked conditions) and when it is unidentifiable due to forward masking (masked conditions). Word acceptance is slowed by a phonemically similar context that is not masked but hastened by a phonemically similar context that is masked. Word acceptance is hastened by an associatively related context that is not masked; this facilitation is somewhat diminished when the context is masked. Finally, word acceptance is hastened by a grammatically related context that is not masked but is unaffected when the grammatical context is masked. These results can be rationalized in terms of a model of the language processor that maintains the autonomy of prelexical and postlexical levels but permits interaction among prelexical components.

Static depiction of movement.

A number of pictorial devices were compared in order to assess their relative effectiveness in depicting events. Effectiveness, as measured by a rating task, did not seem to be a function of the classification of a device as natural or metaphorical. Rather, it depended on whether a given device highlighted a distinctive aspect of a particular event (running, jumping, or moving), or simply modified the event. This observation was buttressed by the existence in a forced-choice task of a category boundary for depictions of running (pictures with a certain device were seen as running, those without it were not) but not for moving or jumping. Even preschool children displayed some understanding of metaphorical devices. They chose figures with those devices as running faster than the experimental standard. Results are discussed in the context of Kennedy's characterization of pictorial metaphors and Gibson's framework for understanding the relationship between pictorial and environmental information.