This study examined the ability to perceive surface separation on the basis of mechanical stimulation resulting from striking the surfaces' interiors with a hand-held rod. The variables manipulated were aperture size, angular displacement theta, distance b of the point of contact with the surfaces from the axis of rotation, hand-rod mass m, location of the hand-rod's center of mass a, and moment of inertia Io of the hand-rod. Given a particular rod and an aperture at a given distance, lambda = sin(theta/2)[1 - (2a/b) + (ma2/Io)] was invariant over explorations. Perception of aperture size was specific to lambda; it predicted successfully the interdependent effects of theta, b, and the mechanical properties of the implement. The results of 7 experiments were discussed in terms of the specificity of perception to information and the general ability to perceive distant things by means of body appendages.

We examined the contribution of semantics to morphological facilitation in the visual lexical decision task at two stimulus onset asynchronies (SOAs) with Serbian materials. Primes appeared in Roman or Cyrillic characters. Targets always were printed in Roman. When primes were presented at an SOA of 250 msec, decision latencies to verbal targets (e.g., volim) showed greatest facilitation after inflectionally (e.g., vole) related primes, significantly less after semanticallytransparent derived primes (e.g., zavole), and less again after semantically opaque derived primes (e.g., prevole). Latencies after semantically transparent and opaque derived target words did not differ at an SOA of 48 msec. Both were slower than after inflectionally related primes. Stated generally,effects of semantic transparency among derivationally related verb forms were evident at long SOAs, but not at short ones. Under alphabetalternating conditions, magnitudes of facilitationwere greater overall,but the pattern was similar. The outcome suggests that restrictedprocessing time for the prime limits the contribution of semantics to morphological processing and calls into question accounts that posit a task-invariant semantic criterion for morphological decomposition within the lexicon.

Children with developmental speech disorders may have additional deficits in speech perception and/ or short-term memory. To determine whether these are only transient developmental delays that can accompany the disorder in childhood or persist as part of the speech disorder, adults with a persistent familial speech disorder were tested on speech perception and short-term memory. Nine adults with a persistent familial developmental speech disorder without language impairment were compared with 20 controls on tasks requiring the discrimination of fine acoustic cues for word identification and on measures of verbal and nonverbal short-term memory. Significant group differences were found in the slopes of the discrimination curves for first formant transitions for word identification with stop gaps of 40 and 20 ms with effect sizes of 1.60 and 1.56. Significant group differences also occurred on tests of nonverbal rhythm and tonal memory, and verbal short-term memory with effect sizes of 2.38, 1.56 and 1.73. No group differences occurred in the use of stop gap durations for word identification. Because frequency-based speech perception and short-term verbal and nonverbal memory deficits both persisted into adulthood in the speech-impaired adults, these deficits may be involved in the persistence of speech disorders without language impairment.

Six experiments are reported on perceiving the sizes of gaps by probing with a hand-held rod. A collective parameter, lambda, is invariant over the time-varying dynamics of probing: lambda = sin(alpha/2)[1-(2a/b) + (a/p)] = sin(alpha/2) delta, where alpha is the angular excursion of the rod-plus-limb segment and a, b, and p are the distances, respectively, of the center of mass, point of contact, and the center of percussion from the axis of rotation. If perceived size is specific to lambda, then it should (a) be a single-valued function of lambda regardless of the muscles executing, and deformed by, the probing; (b) equal, underestimate, and overestimate actual size according to 2b/delta = 1, 2b/delta < 1, and 2b/delta > 1, respectively; and (c) change with actual size at a rate equal to (1/2b-a/b2 + a/2bp), the partial derivative of lambda with respect to size. The experimentally confirmed predictions are discussed in relation to hypotheses about the specificity of perception to information, and the tensorial nature of dynamic touch.