Giovanni F. Misceo

A conditioned weight illusion: Reafference learning without a correlation store

Each of 20 female college students repeatedly judged the weight of a heavy metal cylinder dropped repeatedly (180 times) into her waiting hand. The cylinder came to appear lighter to her when the release of the cylinder was accompanied by the onset of an indicator lamp than when it was not, but only providing the onset of the lamp preceded the release of the cylinder by a half second rather than being simultaneous with it. This conditional illusion has implications for von Holst and Mittelstaedt’s well-known thesis that every neural efference leaves an efference copy or corollary discharge of itself in the nervous system to be compared with concurrent neural reafference. Apparently some types of conditioned-efference leave no copies, and objects lifted in part by such unregistered efforts appear lightened accordingly. The illusion illustrates a form of reafference learning that need involve no correlation store (Held, 1961).

TOUCH DOMINATES HAPTIC ESTIMATES OF DISCORDANT VISUAL-HAPTIC SIZE

Observers (72 college students) estimated the size of plastic squares that they held in their fingers and simultaneously viewed through a reducing lens that halved the squares’ visual size. The squares were grasped from below through a cloth that prevented direct sight of the hand. Each estimate was a match selected later, either haptically or visually, from a set of comparison squares. Vision dominated the visual estimates and touch dominated the haptic estimates, whether or not the observers knew in advance which type of estimate they would be asked to make. Neither modality inherently dominates perceived size.

Size scaling in two-dimensional pictorial arrays

The study examined effects of instructional sets (objective, phenomenal, projective, and retinal) on the judged sizes of blocks placed at various “distances” in a pictorial array. Magnitude estimations of size were consistent with previous studies of size constancy in three-dimensional arrays. Chronometric analyses indicated that reaction time increased with distal size, but was not affected by perceived distance. The results suggested that size was scaled relative to a perceptual unit. Instructions affected the nature of the scale unit (proximal vs. distal), but not the scaling process itself.

Again, knowledge of common source fails to promote visual-haptic integration.

The present study tested whether knowledge of a common source of conflicting visual-haptic stimulation promotes intersensory integration. 40 undergraduates manually felt the size of a square while viewing it through a lens that minified its visual size by half. Participants, however, could experience the haptic and the visual stimulation as emanating from either a common source or different sources. Their subsequent matches of the perceived size were biased by the felt size of the square, irrespective of whether they experienced the intersensory stimulation as coming from one or two sources. These results strengthen previous findings suggesting that the integration of sensory discordant information depends on bottom-up rather than on top-down processes.

Practise strengthens haptic capture.

When do haptic estimates of discordant visual-haptic size capture vision? Observers looked at a square through a minifying lens (50%) whilst they simultaneously touched the square from below through a hand-concealing cloth. Their subsequent match of the squares size, rendered by touching a set of comparison squares, was haptically biased when they practised estimating the squares size (Experiment 1, N = 72), when they actively explored rather than passively touched the square (Experiment 2, N = 24), but not when they were uninformed before inspecting the square that they would estimate its size (Experiment 3, N = 36). Evidently, the haptic exploratory strategies occasioned by the practise influenced the integration of the felt size and the seen size by weighing the haptic input more than the visual input, and this weight shifting manifested itself by strengthening haptic capture.

History of Psychology: XXXIII. On Textbook Lessons from History, or How the Conditioned Reflex Discovered Twitmyer

A number of recent textbooks have claimed that the American psychologist E. B. Twitmyer discovered the conditioned reflex in 1902 independently of and even prior to Pavlov. Various explanations for the obscurity of Twitmyers discovery were offered. However, closer scrutiny of Twitmyers publications, viewed in their contemporary context, does not find much support for such speculative explanations. It is argued that Twitmyers work with the knee jerk constituted neither a knowing nor an unknowing discovery of the “conditioned reflex.” Instead a retrospective and anachronistic view of history, employing an overly simple notion of discovery and a reified concept of the conditioned reflex, had discovered Twitmyer in order to teach some “lessons from history.”

Touch Precision Modulates Visual Bias

ABSTRACT The sensory precision hypothesis holds that different seen and felt cues about the size of an object resolve themselves in favor of the more reliable modality. To examine this precision hypothesis, 60 college students were asked to look at one size while manually exploring another unseen size either with their bare fingers or, to lessen the reliability of touch, with their fingers sleeved in rigid tubes. Afterwards, the participants estimated either the seen size or the felt size by finding a match from a visual display of various sizes. Results showed that the seen size biased the estimates of the felt size when the reliability of touch decreased. This finding supports the interaction between touch reliability and visual bias predicted by statistically optimal models of sensory integration.

Apparent movement in phenomenal space.

The spatial and temporal variables in Korte’s third law of apparent movement were studied in pictorial arrays in which size constancy could be expected to prevail. The thresholds for apparent movement were determined under conditions in which two squares appeared on a plane either with or without perspective information for depth. The results suggest that apparent movement varies with the perceived depth separation only if the size of the stimulus pair is congruent with contextual depth representations. The obtained psychophysical function relating thresholds for third-dimensional movement to pictorial depth scale supports the view that apparent movement preserves gradient-of-texture information.