The role of central and peripheral vision in perceiving the direction of self-motion.

Three experiments were performed to examine the role that central and peripheral vision play in the perception of the direction of translational self-motion, or heading, from optical flow. When the focus of radial outflow was in central vision, heading accuracy was slightly higher with central circular displays (10 degrees-25 degrees diameter) than with peripheral annular displays (40 degrees diameter), indicating that central vision is somewhat more sensitive to this information. Performance dropped rapidly as the eccentricity of the focus of outflow increased, indicating that the periphery does not accurately extract radial flow patterns. Together with recent research on vection and postural adjustments, these results contradict the peripheral dominance hypothesis that peripheral vision is specialized for perception of self-motion. We propose a functional sensitivity hypothesis--that self-motion is perceived on the basis of optical information rather than the retinal locus of stimulation, but that central and peripheral vision are differentially sensitive to the information characteristic of each retinal region.     

Extracting thresholds from noisy psychophysical data.

Psychophysical studies with infants or with patients often are unable to use pilot data, training, or large numbers of trials. To evaluate threshold estimates under these conditions, computer simulations of experiments with small numbers of trials were performed by using psychometric functions based on a model of two types of noise: stimulus-related noise (affecting slope) and extraneous noise (affecting upper asymptote). Threshold estimates were biased and imprecise when extraneous noise was high, as were the estimates of extraneous noise. Strategies were developed for rejecting data sets as too noisy for unbiased and precise threshold estimation; these strategies were most successful when extraneous noise was low for most of the data sets. An analysis of 1,026 data sets from visual function tests of infants and toddlers showed that extraneous noise is often considerable, that experimental paradigms can be developed that minimize extraneous noise, and that data analysis that does not consider the effects of extraneous noise may underestimate test-retest reliability and overestimate interocular differences.     

A novel contact-lens system to assess visual hemispheric asymmetries.

A soft contact-lens system for achieving unilateral visual stimulation in a free vision format is described. Initial testing with light transmittance and visual perimetry indicated that the lenses created artificial visual-field deficits. The efficacy of the lenses as a technique for lateralizing visual input was evaluated by examining within-subject differences in performance on two visuospatial tasks. Speed and accuracy of performance were greater with visual input directed to the right hemisphere. These data support the lens design as a useful alternative to tachistoscopic procedures and previous lens systems.     

An automated test development of parallel tests from a seed test

Binary programming models are presented to generate parallel tests from an itembank. The parallel tests are created to match item for item an existing seed test and match user supplied taxonomic specifications. The taxonomic specifications may be either obtained from the seed test or from some other user requirement. An algorithm is presented along with computational results to indicate the overall efficiency of the process. Empirical findings based on an itembank for the Arithmetic Reasoning section of the Armed Services Vocational Aptitude Battery are given.The Office of Naval Research, Program in Cognitive Science, N00014-87-C-0696 partially supported the work of Douglas H. Jones. The Rutgers Research Resource Committee of the Graduate School of Management partially supported the work of Douglas H. Jones and Ing-Long Wu. A Thomas and Betts research fellowship partially supported the work of Ing-Long Wu. The Human Resources Laboratory, United States Air Force, partially supported the work of Ronald Armstrong. The authors benefited from conversations with Dr. Wayne Shore, Operational Technologies, San Antonio, Texas. The order of authors' names is alphabetical and denotes equal authorship.     

Change in the event-related skin conductivity: an indicator of the immediate importance of elaborate information processing?]

In recent psychophysiological conceptualizations of the orienting response (OR) within the framework of information processing, the OR is increasingly considered a "call for processing resources", something which is especially inferred from variations in the event-related skin conductance response (SCR). The present study, therefore, was concerned with certain implications arising from this framework or perspective, particularly in regard to the question of whether stimuli eliciting skin conductance responses obligatorily receive/evoke processing priority or not. In order to examine whether these electrodermal responses denote a capturing of attention or merely a call for processing resources, short (1 s) pure sine tones of 65 dB with sudden onset (commonly used as orienting stimuli) were inserted in a reaction time paradigm with an additional memory load. This demand was primarily given because memory processes play a key role in theories of orienting and habituation. The task was run under two different conditions of complexity, factorially combined with a novelty variation of the added auditory stimuli. The results revealed a substantial deterioration of task performance subsequent to the occurrence of the tones, which, however, was dependent on task complexity and on novelty of the tones. The task impairment is particularly remarkable as subjects were asked to avoid distractions by paying attention to the task and as the tones were introduced as subsidiary and task-irrelevant. Together with the missing effects of task complexity on phasic and tonic electrodermal activity, results suggest that information-processing conceptualizations of the OR can only be a meaningful heuristic contribution to theoretical developments about human orienting and its habituation if the setting of processing priority, its conditions, as well as its implications are adequately taken into account. In addition, it seems to be promising to consider the strength of the SCR as an index of urgency of elaborate, attention-demanding processing and not as a peripheral physiological manifestation of the OR, or, respectively, of a call for unspecific processing resources. Such a view would also do justice to the aspect of prioritization. The sufficient conditions for an OR's occurrence could, in this context, be equated with, among others, some of those which activate a mechanism subserving selective attention and, as a possible result, which lead to further and more elaborate processing of potentially important information.     

Discrimination learning of rotated faces: a Markov analysis of coding and association processes]

30 subjects participated in a discrimination experiment learning face-letter associations under four rotation conditions (45 degrees, 90 degrees, 135 degrees, 180 degrees). Under each condition two thirds of the faces were presented twice, upright and rotated away from the vertical; the remaining faces were presented once, upright or rotated. Learning is described by a joint Markov model: For faces that are presented twice it assumes a separate association and encoding process (two-stage-model), for faces that are presented once it assumes an association process (all-or-none-model). The Markov model fits the data for all four rotation conditions. The angle of rotation does not affect learning for faces that are presented once. For faces that are presented twice it influences both the association and the encoding process. For the angles employed, the effect of rotation can be approximated linearly. The results suggest that the encoding of a rotated face differs increasingly from an upright face as a function of these angles of rotation. This confirms analogous conclusions from mental rotation experiments.     

Sentence encoding and implicitly activated memories

Some words have fewer direct associates than others, and, when words varying in set size are studied in a list-learning task, those with smaller sets are more likely to be recalled. This set-size effect is found in cued recall when the words are studied in the absence of related words, but not when studied in the presence of related words. Related words provide context and theoretically inhibit irrelevant associates. The present research determined that set-size effects are found when words are encoded in sentence contexts. In contrast to list-learning experiments, the results of three experiments found such effects even when lexically related words were present in the sentences. Other findings indicated that target-set-size effects were determined by the proximity of related words in the sentence and the nature of the test cue. The results are discussed in relation to a model for explaining set-size effects and to selective findings from the sentence-comprehension literature.     

A developmental evaluation of the role of word shape in word recognition

Fourth- and seventh-grade children and college-age adults proofread passages typed either in lowercase or in all capital letters. Words were misspelled by deleting one of four letters, s, c, k, or p, that have similar features in lowercase and uppercase. Proofreading errors decreased with age and increasing reading ability, but all of the subjects were sensitive to changes in word shape--they missed more words with deletions of s or c than k or p in the lowercase passage but not in the all-capitals passage. These findings indicate that word shape is an important variable in recognizing familiar words, even for young readers.     

A psychophysiological study of the use of partial information in stimulus-response translation.

Ss performed a hybrid go/no-go reaction task in which colored letters were assigned in various ways to 4 finger responses, 2 on each hand. In addition to reaction time, psychophysiological measures were used to assess the duration of stimulus identification and the onset of central and peripheral motor activity. The results suggest that response selection can begin on the basis of 1 stimulus dimension (e.g., color), while the other dimension (e.g., letter form) has not yet been identified. Other results are discussed with regard to "selection for action" (Allport, 1987) and the importance of stimulus-response translation strategies in the use of partial information.     

Influence of animation on dynamical judgments.

The motions of objects in the environment reflect underlying dynamical constraints and regularities. The conditions under which people are sensitive to natural dynamics are considered. In particular, the article considers what determines whether observers can distinguish canonical and anomalous dynamics when viewing ongoing events. The extent to which such perceptual appreciations are integrated with and influence common-sense reasoning about mechanical events is examined. It is concluded that animation evokes accurate dynamical intuitions when there is only 1 dimension of information that is of dynamical relevance. This advantage is lost when the observed motion reflects higher dimension dynamics or when the kinematic information is removed or degraded.