Visual and tactual form discrimination: Psychophysical comparison within and between modalities

Intermodal perceptual equivaience was investigated, using visual and tactual oddity discrimination and cross-modal matching-to-sample tasks. Four groups of Ss were presented with 100 problems made up of randomly derived forms from five levels of sidedness. The same quadratic relationship was observed for all tasks as a function of complexity, with optimal performance at eight sides. Comman information utilization, as indicated by intercorrelations of performance variables and by correlational analyses with differences in form measures, was not as pronounced within side classes. Evidence concerning the nature of pattern-feature usage in discrimination was obtained from graphical analyses.     

A Truncated-Probit Item Response Model for Estimating Psychophysical Thresholds

Human abilities in perceptual domains have conventionally been described with reference to a threshold that may be defined as the maximum amount of stimulation which leads to baseline performance. Traditional psychometric links, such as the probit, logit, and t, are incompatible with a threshold as there are no true scores corresponding to baseline performance. We introduce a truncated probit link for modeling thresholds and develop a two-parameter IRT model based on this link. The model is Bayesian and analysis is performed with MCMC sampling. Through simulation, we show that the model provides for accurate measurement of performance with thresholds. The model is applied to a digit-classification experiment in which digits are briefly flashed and then subsequently masked. Using parameter estimates from the model, individuals’ thresholds for flashed-digit discrimination is estimated.     

Cerebral Asymmetry and Decision Strategies in Mental Rotation: A Psychophysical Analysis

The accuracy with which observers judged the parity of pairs of rotated images in the two visual fields was determined from receiver operating characteristic (ROC) analysis of confidence ratings. In one experiment, observers judged whether pairs of letters were of the same parity (that is, both normal or both backwards) or of different parities (one normal and one backwards). A small right visual field advantage in the observers' accuracy was found in this mental rotation task. In a second experiment, observers judged whether pairs of pictures were of the same parity or of different parities. Unlike the first experiment, no evidence of a consistent visual field advantage was found in this mental rotation task. The decision strategy adopted by the observers in making same-different judgements about rotated stimuli was examined. The symmetrical shape of the ROCs obtained was consistent with the adoption of the likelihood-ratio decision strategy, a result which supplemented previous evidence that this decision strategy is adopted when same-different judgements are made about multidimensional stimuli.     

Psychophysical magic: rendering the visible 'invisible'

What are the neural correlates of conscious visual awareness? Tackling this question requires contrasting neural correlates of stimulus processing culminating in visual awareness with neural correlates of stimulus processing unaccompanied by awareness. To produce these two neural states, one must be able to erase an otherwise visible stimulus from awareness. This article describes and assesses visual phenomena involving dissociation of physical stimulation and conscious awareness: degraded stimulation, visual masking, visual crowding, bistable figures, binocular rivalry, motion-induced blindness, inattentional blindness, change blindness and attentional blink. No single approach stands above the others, but those producing changing visual awareness despite invariant physical stimulation are clearly preferable. Such phenomena can help lead us ultimately to a comprehensive account of the neural correlates of conscious awareness.     

A Predictive Approach to Nonparametric Inference for Adaptive Sequential Sampling of Psychophysical Experiments

We present a predictive account on adaptive sequential sampling of stimulus-response relations in psychophysical experiments. Our discussion applies to experimental situations with ordinal stimuli when there is only weak structural knowledge available such that parametric modeling is no option. By introducing a certain form of partial exchangeability, we successively develop a hierarchical Bayesian model based on a mixture of Pólya urn processes. Suitable utility measures permit us to optimize the overall experimental sampling process. We provide several measures that are either based on simple count statistics or more elaborate information theoretic quantities. The actual computation of information theoretic utilities often turns out to be infeasible. This is not the case with our sampling method, which relies on an efficient algorithm to compute exact solutions of our posterior predictions and utility measures. Finally, we demonstrate the advantages of our framework on a hypothetical sampling problem.     

On predicting exponents for cross-modality matches

Mashhour and Hosman used magnitude estimations to scale seven continua: line length, time duration, finger span, loudness of noise, weight, gray reflectance, and surface area. The first four continua also served as the adjusted stimuli in 17 cross-modality matches among the various continua. Contrary to the view expressed by Mashhour and Hosman, the results appear to support the psychophysical power law. A reanalysis of the data shows that the exponents of the power functions obtained in cross-modality matches agree with the exponents of the power functions produced by magnitude estimations, provided correction is made for the regression effect. The measured discrepancies between the exponents predicted and those actually obtained show scatter that is consistent with that of other experiments. In particular, the scatter accords well with the distribution of 68 exponents predicted by Moskowitz from experiments in which Os matched both number and loudness to various taste concentrations.     

Psychophysical isolation of the modality responsible for detecting multimodal stimuli: a chemosensory example

Multiple sense modalities can be stimulated conjointly by a physically complex item, such as a predator, and also by a physically solitary stimulus that acts on multiple receptor classes. As a prime example of this latter group, l-menthol from mint stimulates taste, smell, and several somatosensory submodalities. In 6 experiments that used a variety of psychometric techniques, the authors experimentally isolated the modality by which l-menthol is detected in the upper airways (the nose and mouth). Interestingly, absolute detection in both the nasal and oral cavities was based on olfaction and not stinging, cooling, or taste. These experiments illustrate how the sensory modality responsible for detecting a multimodal or multisensory stimulus can be psychophysically isolated.     

Eyewitness misidentification: single vs. double-blind comparison of photospread administration

Interactive effects of photospread procedures (blind administration or has knowledge of suspect identity) and presentation techniques (sequential or simultaneous photospreads) on false eyewitness identification rates were examined. Of 117 subjects (57 men and 60 women), 87 served as a witness sample and 30 as a photospread administrator sample. Witnesses viewed a 20-sec. mock robbery video prior to viewing a photospread of six photographs either simultaneously or sequentially. Half of the administrators, prior to displaying the photospreads, were made aware of the photograph of the designated suspect (single-blind condition). Consistent with previous findings, sequential presentation was associated with both lower overall false identification rates as well as lower suspect designated-misidentification rates. In each case, there was evidence that administrators' knowledge increased false identification rates more in simultaneous than in sequential presentation conditions. Implications for administrations by police investigators are discussed.     

Preference for reinforcers under progressive- and fixed-ratio schedules: a comparison of single and concurrent arrangements

Progressive-ratio (PR) schedules were used to identify the break point (i.e., the last schedule value completed) for 2 reinforcers under single and concurrent schedules. After the respective break points were established, the same reinforcers were presented under concurrent fixed-ratio (FR) schedules that were yoked to the break points obtained with the PR schedules. Results suggested that the participants responded more for the high-preference item than for the low-preference item, regardless of the presentation arrangement (single or concurrent presentations). This pattern of responding was maintained when the reinforcers were presented under dissimilar FR schedules. The results suggest that responding for differentially preferred stimuli may vary as a function of differences in schedule requirements.     

Help-seeking for AIDS-related concerns: A comparison of gay men with various HIV diagnoses

Examined help-seeking and psychological distress among four groups of gay men (30 AIDS-diagnosed, 107 HIV-seropositive, 149 HIV-seronegative, 244 untested) in the AIDS Behavioral Research Project, a longitudinal survey of San Francisco gay men. The men reported high levels of anxiety, depression, and help-seeking from their social networks. AIDS-diagnosed and HIV-positives reported the most AIDS worry and were the most likely to seek help. High percentages of AIDS-diagnosed men sought help from all sources (peers, professionals, family), whereas nondiagnosed men were more likely to seek help from peers. Regardless of the men's HIV status, peers were perceived to be the most helpful source. Family members were less likely sought and perceived as least helpful. The strengths and limitations of peers as social support providers for AIDS-related concerns are discussed, including implications for the design of community programs to enhance the abilities of peer helpers.     

Short-term memory for spatial configurations in the tactile modality: A comparison with vision

This study investigates the role of acquisition constraints on the short-term retention of spatial configurations in the tactile modality in comparison with vision. It tests whether the sequential processing of information inherent to the tactile modality could account for limitation in short-term memory span for tactual-spatial information. In addition, this study investigates developmental aspects of short-term memory for tactual- and visual-spatial configurations. A total of 144 child and adult participants were assessed for their memory span in three different conditions: tactual, visual, and visual with a limited field of view. The results showed lower tactual-spatial memory span than visual-spatial, regardless of age. However, differences in memory span observed between the tactile and visual modalities vanished when the visual processing of information occurred within a limited field. These results provide evidence for an impact of acquisition constraints on the retention of spatial information in the tactile modality in both childhood and adulthood.     

Neuromuscular control in individuals with chronic ankle instability: A comparison of unexpected and expected ankle inversion perturbations during a single leg drop-landing

While neuromuscular control deficits during inversion perturbations in chronic ankle instability (CAI) cohorts are well documented in the literature, anticipatory motor control strategies to inversion perturbations in CAI are largely unknown. The purpose of this study was to examine neuromuscular control and ankle kinematics in individuals with CAI (n = 15) and matched controls (n = 15) during unexpected and expected single leg drop-landings onto a tilted surface rotated 20° in the frontal plane. Muscle activity from 200 ms pre- to post-landing was recorded from the tibialis anterior (TA), medial gastrocnemius (MG), peroneus longus (PL) and peroneus brevis (PB). Mean muscle activity, co-contraction index (CCI), and peroneal latency was analyzed. Ankle inversion angle at initial contact, time to maximum inversion angle, maximum inversion angle and velocity were also assessed. Significantly longer PL latency, less time to maximum inversion and greater maximum inversion angle was found in CAI compared to controls. Regarding landing condition, significantly greater maximum inversion angle, less inversion at initial contact, longer PB latency, less TA activity and frontal plane CCI during the post-landing phase was found during the unexpected perturbation. Prolonged PL latency and altered ankle kinematics suggests reduced frontal plane ankle stabilization in CAI. However, similar motor control strategies were utilized in both groups during the ankle inversion perturbations.     

A comparison of intraverbal training procedures for children with autism

We compared the effectiveness of three training procedures, echoic and tact prompting plus error correction and a cues-pause-point (CPP) procedure, for increasing intraverbals in 2 children with autism. We also measured echoic behavior that may have interfered with appropriate question answering. Results indicated that echoic prompting with error correction was most effective and the CPP procedure was least effective for increasing intraverbals and decreasing echoic behavior.     

Dry-bed training for childhood bedwetting: A comparison of group with individually administered parent instruction

Thirty nocturnally enuretic children and their parents took part in this study which examined the effectiveness of Dry-Bed Training (DBT) with and without the adjunct of a urine-alarm device. Parents administered all treatment, following initial instruction in small group settings and supported by regular group meetings with a professional therapist. Ten children were treated by DBT without an alarm. Results showed this method to be effective in significantly reducing bedwetting frequency but not in effecting complete arrest of bedwetting symptoms. Ultimately all 30 children were treated by DBT with an alarm and this method led to 29 children reaching the success criterion of 14 consecutive dry nights. The average time taken to the last wet night was 30 days. There were 10 relapses at a 3-month follow-up. These results were virtually the same as those from a previous study involving 60 subjects who were treated by DBT with an alarm, either under the direction of a professional therapist, or of the child's parents who had been previously trained in the procedure on an individual basis (Bollard and Nettelbeck, 1981). Instructing parents in a group to administer DBT with an alarm is therefore an economical large-scale method of treating nocturnal enuresis because of savings in therapist time and effort in administering the demanding procedure.     

A comparison between two treatment programs for stuttering: A personal account

This article features a personal evaluation of two treatment methods for stuttering, the Precision Fluency Shaping Program (PFSP) (Webster, 1990; 1986), and the Comprehensive Stuttering Program (CSP) (Boberg and Kully, 1985). The CSP program is described as promoting natural-sounding speech by focusing, from the outset, on smooth blending of syllables or within breath groups. The PFSP program is described as tending to focus on syllables or words in isolation, particularly during early stages of instruction. In addition, the Boberg/ Kully program featured individualized instruction by a series of clinicians interacting with clients in accordance with a rotating schedule. In contrast, the PFSP program emphasized solitary interaction with a voice monitor and client manual. Differences in timing of instruction and calculation of speech rates are discussed. Treatment refinements are suggested, including enhanced precision in distinguishing between soft phrase onsets on individual words.     

Children's attributions for peer victimization: A social comparison approach

A social comparison framework was used to examine the relations between children's attributions for victimization and adjustment. In Study One, 192 nine-to ten-year-old children were asked why someone may pick on them. Results revealed attributions reflecting five causes of victimization that could be reliably sorted by direction of social comparison: (a) jealous peer (downward), (b) mutual antipathy (horizontal), (c) being different from each other (horizontal), (d) personal behavior (upward) and (e) being uncool (upward). Children's responses were used to create an attribution measure that was administered to 206 eight-to eleven-year-old children. Results were consistent with the social comparison hypothesis such that peer jealousy was uniquely associated with lower levels of loneliness and greater acceptance whereas personal behavior and not being uncool were correlated with greater loneliness and lower perceived acceptance and self-esteem. Findings supported the usefulness of a social comparison framework for understanding associations among attributions and adjustment.