Integration of information from multiple element displays

This experiment examined the processing of information from multiple element visual displays, using techniques derived from the theory of signal detectability. The method allows one to specify how observers integrate information from individual elements of a display. The experiment tested numerical and graphical displays having different display sizes, durations, and arrangements of elements. Observer performance increased with the number, m, of display elements, but at less than the ideal √m rate. Observer performance was consistent with a model of information integration constrained by internal noise. Linear arrays of elements resulted in better performance than did square arrays. Graphically coded elements resulted in better performance than did numerical elements. Observer decision weighting of element information from graphical displays was approximately uniform across spatial position, but the weighting of information from numerical displays was concentrated on elements near the fixation point.     

Adolescents' perceptions of friends' and parents' attitudes to sex and sexual risk-taking

This study investigated the association between adolescents' perceptions of parental and peer attitudes towards sexuality and AIDS precautions, and the risky sexual behaviours of 1008 sexually active, heterosexual undergraduate students aged 17-20 years. Students were asked to rate the extent to which their mothers, fathers and friends would agree or disagree with 16 statements reflecting support of the adolescent engaging in sexual behaviour and using sexual precautions, including precautions against AIDS. The adolescents also indicated whether they were sexually active and their level of condom use in both ‘regular’ (or steady) and ‘casual’ relationships. Results indicated that adolescents perceived their parents as non-liberal in their sexual attitudes and relatively unlikely to discuss sex or precautions with them. Parents were viewed as more accepting of their sons' sexual behaviours than of their daughters'. Adolescents believed that peers were more likely to discuss sexuality and precautions than parents, and were more liberal in their sexual attitudes. Adolescent sexual risk-taking was related to the perceived attitudes of significant others in ways which varied across gender and type of relationship. Implications for interventions are discussed.     

Improving the retrieval of information from external sources

A major barrier to successful retrieval from external sources (e.g., electronic databases) is the tremendous variability in the words that people use to describe objects of interest. The fact that different authors use different words to describe essentially the same idea means that relevant objects will be missed; conversely, the fact that the same word can be used to refer to many different things means that irrelevant objects will be retrieved. We describe a statistical method called latent semantic indexing, which models the implicit higher order structure in the association of words and objects and improves retrieval performance by up to 30%. Additional large performance improvements of 40% and 67% can be achieved through the use of differential term weighting and iterative retrieval methods.     

Duration discrimination of filled and empty auditory intervals: Cognitive and perceptual factors

Adult subjects were presented with two auditory stimuli per trial, and their task was to decide which of the two was longer in duration. An adaptive psychophysical procedure was used. In Experiments 1, 2, and 4, the base duration was 50 msec, whereas in Experiment 3, the base duration was 1 sec. In Experiments 1, 2, and 4, it was found that filled intervals (continuous tones) were discriminated more accurately than empty intervals (with onset and offset marked by clicks). It was concluded that this difference was perceptual rather than cognitive in nature, since performance on filled and empty intervals was not affected by increasing cognitive load in a dual-task procedure (Experiment 2) but was affected by backward masking (Experiment 4). In contrast, the results of Experiment 3 showed that duration discrimination of filled auditory intervals of longer duration was cognitively influenced, since performance was impaired by increasing cognitive load. Implications for notions of perceptual processing and timing mechanisms tanderlying differences in duration discrimination with filled and empty intervals are discussed.     

Interpreting idioms

Immediate comprehension processes involved in the interpretation of idiomatic expressions were investigate. Idioms like bury the hatchet were used in sentential contexts that (1) biased the listener toward a literal interpretation, (2) biased the listener toward a figurative interpretation, or (3) left the interpretation ambiguous between the literal and figurative readings. In control sentences, the final words of the idioms were used in nonidiomatic expressions. Listeners monitored the sentences for specified targets. In all cases, the target words were the final words of the idiomatic phrases. The listeners were instructed to detect words that were identical to cue words, that rhymed with the cue words, or that were members of semantic categories specified by cue words. Thus, hatchet was cued with either hatchet, ratchet, or a tool. Reaction-time latencies from the onset of the targets to the listeners' responses were obtained. Identity, Rhyme, and Category matches were detected more rapidly in all three idiomatic contexts than in the nonidiomatic controls. These results suggest that idioms are automatically processed as discrete lexical entries, and that previously observed reaction time advantages for figurative expressions may reflect integrative processes rather than retrieval of meaning.This research was supported by PHS Training Grant T32 MH 15134-02 from the National Institute of Mental Health. A preliminary version of this paper was presented at the Annual Meeting of the American Psychological Association, Los Angeles, August 1981.     

Vocal changes in stutterers and nonstutterers when speaking to children

Within the last few years, considerable attention has been devoted to the possibility that the amelioration of stuttering in many novel speaking conditions is a function of vocal changes with or without accompanying modifications in prosodic expression. These formulations have made reference primarily to conditions in which stutterers were induced into one or another novel speech pattern by an external stimulus such as masking noise, a rhythmic cue, or by instructions to sing, or read in unison with another speaker. In contrast, far less attention has been paid to other ameliorative conditions that lack a novel external stimulus or special instructions that direct the stutterer to speak in some unique manner. Speaking or reading to a child is an example of this latter type of condition. The present study was conducted to see if nine adult stutterers and a matched group of nonstutterers would evince vocal changes as they read aloud to another adult, a child, and a child and adult together. There was also a fourth control condition wherein the subjects read to one of the experimenters. Dependent measures of disfluency and stuttering, fundamental frequency, fundamental frequency deviation, fluent reading rate, and peak vocal sound pressure level were made and treated statistically. The major findings of this study indicated that, relative to the control condition, both subject groups exhibited several vocal changes when reading to a child alone and to a child and adult together. In addition, the stutterers experienced a reduction in disfluency, but only when reading to the child alone. The normal speakers exhibited too few disfluencies in the control condition for any meaningful change to occur in that dependent variable. The fact that the stutterers evinced vocal changes in both experimental conditions but a significant drop in disfluency in just one bears importantly on hypotheses that emphasize vocal changes in conditions that ameliorate stuttering.