Levels of selection and capacity limits

Subjects performed a visual target-detection task in eight experiments. We examined the effects of word relevancy (word in relevant or irrelevant location) and display load (1-4 words) on physical, semantic, and controlled processing of nontargets. Interwoven with the detection task was a test-word identification task that was used to measure priming potency of nontargets. Physical and semantic levels of processing were measured in terms of identity and semantic priming, respectively. Nontarget primes were repeated as test words in identity priming. Nontarget primes were semantic associates of test words in semantic priming. Controlled processing of nontargets was measured in terms of recognition memory on a subsequent test. All measures increased with word relevancy and decreased with display load. The priming effects remained intact even when word presentation was speeded up and controlled processing was sharply curtailed. The data indicate that all levels of processing are selective and capacity limited.     

How much is an icon worth?

We report a new technique for assessing the amount of information extracted from the icon that follows a briefly presented picture. The problem of how to measure such information was formulated in terms of how much physical exposure of a picture an icon is worth. Consider two types of stimulus presentations, each with a base duration of d ms. The first is a d-ms picture followed by an icon, and the second is a d + a-ms picture not followed by an icon. How large does a have to be so that equivalent amounts of information are extracted in the two cases? To answer this question, we showed people pictures and later tested their memory for the pictures. We found that the physical exposure duration needed to reach a particular level of performance was approximately 100 ms longer when an icon was not permitted versus when the icon was permitted. This value was independent of the base duration and the luminance of the picture. Moreover, the same value was obtained using three different kinds of memory test and four different sets of pictures. We conclude that an icon is worth approximately 100 ms of additional physical exposure duration. A reasonable explanation for this robust equivalence between icon and stimulus is that the same encoding processes are responsible for extracting information from the icon and from the physical stimulus. Therefore, any variable that affects these encoding processes must affect extraction of information from the icon and the physical stimulus in an identical manner. This prediction was confirmed for one such variable, picture luminance.     

Effect of classical conditioning on an internal clock

Six experiments with rats used a psychophysical choice procedure to study the internal clock used to discriminate duration. They investigated if the clock is sensitive to the signal value (associative strength) of a stimulus. The experiments involved two types of trials. On choice trials, a stimulus lasted a short (e.g., 3 s) or long (e.g., 12 s) duration; then the rats chose between two levers. The rewarded choice depended on the duration of the stimulus. On conditioning trials, the stimulus used on choice trials was presented, but it ended without food (extinction trials) or with food (pairing trials) regardless of what the rat did. The main stimulus minus accuracy with the long stimulus. Experiment 1 showed that extinction trials increased short bias relative to training without conditioning trials or to training with pairing trials. The rest of the experiments tested explanations of these results. The same results were found when extinction trials were the same duration as the short stimulus (Experiment 2), when extinction trials were a random duration (Experiment 5), and when the signal value of the conditioned stimulus was changed in another way (Experiment 6). The effect of conditioning trials was modality specific (Experiments 3 and 4). Of the explanations considered, the best one--the only one not contradicted at least once--is that changing the signal value of a stimulus changes how the clock times the stimulus. Reducing signal value reduces the measured duration.     

Reflex modification in the rat: the inhibitory effects of intensity and frequency changes in steady tones

In laboratory rats (as in humans) a low-intensity tone that precedes a high-intensity burst of noise by approximately 100 ms can reduce the amplitude of the startle reaction elicited by the burst of noise. A series of four experiments with rats investigated the relation between the inhibitory effects of tonal frequency change and the length of the silent period (gap) preceding it. The major findings were the following: (a) A gap in an otherwise continuous pure tone inhibited startle when the gap occurred approximately 100 ms prior to the noise burst. (b) Although an increase in gap duration increased the inhibition afforded by the gap, the maximum inhibition was yielded by gaps of 100 ms and greater; this maximum was equivalent to the inhibition yielded by the presentation of a postgap tone alone. (c) A shift in tonal frequency across a 10-ms gap yielded more inhibition than did the same gap with no frequency shift; again the shift yielded equivalent inhibition to the presentation of the postgap tone alone. (d) An increase in the frequency shift increased inhibition when the shift occurred across a 10-ms gap, but not when the shift occurred across a 100-ms gap.     

Treatment of chronic global aphasia with a nonverbal communication system

Four chronic global aphasics were treated with Blissymbols (C. K. Bliss, 1965, Semantography-Blissymbolics, Sydney: Semantography Pub.). As soon as possible the therapeutic communication was based solely on the use of the symbols. Three patients seemed to benefit from therapy. In one case therapy had to be discontinued because of massive perseveration. In one patient expression of needs relied solely on the use of the symbols. In another, expressive speech could be restored to such an extent that communication by the use of symbols was discontinued.     

The word-superiority effect under conditions that approximate reading

Observers detected a briefly flashed target letter embedded in word, pronounceable nonword, and unpronounceable nonword contexts. The word context facilitated perception under both holistic and analytical processing strategies; the facilitative effect was enhanced when processing was analytical.     

The impact of high school on social development

In reviewing the literature on the social impact of high school, six themes were identified: (1) students perceive strong norms for conformity to school rules, (2) the emphasis on conformity and control influences the quality of student/teacher relations which tend to be role bound and inflexible, (3) paths to social status continue to emphasize athletic competence, (4) peer group identification has an impact on social relations within the larger community as well as in the school setting, (5) powerlessness is felt as a result of the authoritarian approach to decision making, and (6) the overall high school environment does not enhance students' beliefs in the Bill of Rights. It was concluded that high school students have limited opportunities for flexible self-definition. As a result of the way they are treated by authority figures and the strong pressures toward conformity, many adolescents fail to learn the extent of their rights or effective strategies for the exercise of power.     

Young adults' contraceptive practices: an investigation of influences

This study investigated young adults' contraceptive behaviors and attitudes through application of a comprehensive, theoretical framework. Specifically, a social-psychological approach to understanding preventive behaviors (e.g., contraceptive practices), was developed, incorporating the Health Belief Model and other factors, which offered a means for evaluating the extent to which contraceptive behaviors were influenced by individual and group characteristics. The study group consisted of 283 unmarried students at several schools who were, on average, 19 years of age. Results suggested that effective contraceptive behavior associated most strongly with respondents' perceiving relatively few barriers to their use of contraception, their maintenance of extensive interpersonal skills, and their regarding peer norms as consistent with effective contraceptive behavior. Findings also underlined a need for continuing education about sexuality and contraception. Dangerous misinformation prevailed regarding respondents' knowledge of areas that include anatomy, physiology, and appropriate use of effective contraceptive methods. Finally, results implied a need to consider broad behavioral, social, and interpersonal issues as they relate to young adults' effective contraceptive behavior. Future studies of contraceptive risk taking are encouraged to examine both individual and social factors affecting sexual and contraceptive practices if unplanned pregnancy is to be minimized, if not eliminated.