An investigation of planned helping behavior

It is argued that stable, individual differences in helping behavior have not generally been observed in previous research because of the type of helping studied. This paper advocates the study of planned helping behavior as opposed to spontaneous helping behavior. The results of three studies are reported. In Study 1, an instrument designed to measure level of involvement in planned helping activities was developed. Scores on this instrument were found to be stable over a 7-month period. Further analysis revealed two major types of planned helping: (a) formal, organizational helping and (b) informal helping between friends and family. Study 2 examined a variety of intrapsychic and demographic correlates of formal and informal planned helping. Study 3 found support for the hypothesis that people in helping professions have higher levels of involvement in everyday planned helping than do people in nonhelping occupations. It is concluded that the study of planned helping, although posing methodological difficulties, is a necessary adjunct to experimental research.     

Separability and integrality of global and local levels of hierarchical patterns

We used a constrained classification task to examine the perceptual relations between global and local levels in hierarchical patterns composed of many, relatively small elements and those composed of few, relatively large elements. In Experiments 1 and 3 subjects were asked to make classifications based on "form" or "texture." In Experiments 2 and 4 they were asked to classify according to the "shape" of the configuration or the elements. The results indicate that configural and elemental levels are perceptually separable for many-element patterns when processed as form and texture: Subjects could attend to either level without being affected by variation along the irrelevant dimension. However, when the same many-element patterns were processed for global and local shape, subjects could not selectively attend to either level. For few-element patterns, global configuration and local elements appeared to be perceptually integral dimensions. These results are relevant to two issues: the global precedence hypothesis and the explanations of integral and separable dimensions.     

When selective adaptation and contrast effects are distinct: a reply to Diehl, Kluender, and Parker

Two alternative conceptualizations of selective adaptation with speech have recently received attention. The adaptation level theory (AL) outlined by Diehl (1981) and a two-stage model outlined by Sawusch and Jusczyk (1981) can both account for much of the adaptation and paired-comparison data. Recently, Diehl, Kluender, and Parker (1985) proposed that all adaptation and contrast data can be accounted for by AL theory. They reported the results of a study that showed evidence of streaming in selective adaptation and claimed that their results provide a counterdemonstration to recent studies that have argued against the AL approach. In the present article, an outline of how the Diehl et al. results can be accounted for by both the two-stage model and AL theory is presented. In addition, a new set of results comparing adaptation and paired-comparison procedures is presented. These results are precisely as predicted by the two-stage model, but they can not be handled by AL theory.     

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.     

A computational analysis of mental image generation: evidence from functional dissociations in split-brain patients

Recent efforts to build computer simulation models of mental imagery have suggested that imagery is not a unitary phenomenon. Rather, such efforts have led to a modular analysis of the image-generation process, with separate modules that can activate visual memories, inspect parts of imaged patterns, and arrange separate parts into a composite image. This idea was supported by the finding of functional dissociations between the kinds of imagery tasks that could be performed in the left and right cerebral hemispheres of two patients who had previously undergone surgical transection of their corpus callosa. The left hemisphere in both subjects could inspect imaged patterns and could generate single and multipart images. In contrast, although the right hemisphere could inspect imaged patterns and could generate images of overall shape, it had difficulty in generating multipart images. The results suggest a deficit in the module that arranges parts into a composite. The observed pattern of deficits and abilities implied that this module is not used in language, visual perception, or drawing. Furthermore, the results suggest that the basis for this deficit is not a difficulty in simply remembering visual details or engaging in sequential processing.     

Discrimination of letters and random dot patterns by pigeons and humans

In a three-choice discrimination task, pigeons learned to distinguish each letter of the alphabet from all the other letters and each of 16 random dot patterns from all the others. Discrimination errors were used to generate a matrix of interletter and interpattern similarities. Human estimates of letter similarity were obtained from the literature, and human subjects rated the similarity of the dot patterns. Pigeon and human performances were described and compared through correlation, multidimensional scaling, and cluster analysis. Fits of the data by simple-feature and template models were computed and compared. The correlation between pigeon and human similarity matrices was .68 for letters and .72 for dot patterns. The other analyses revealed broadly similar patterns of results from the two species but suggested also that, relative to human data, the best fits to the pigeon data required fewer dimensions, fewer features, and fuzzier templates. There was some indication that pigeon discriminations depended on relatively simple features, and several of these were tentatively identified. The different methods employed might have influenced these apparent differences between pigeons and humans, but, overall, the results suggest considerable cross-task and cross species generality in the processing of these simple forms.     

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.     

Deep dyslexia in childhood?

Deep dyslexia is an acquired reading disorder in which semantic substitutions (e.g., city read as town) are made in reading single isolated words. In this paper, evidence for deep dyslexic-type errors is presented from the word-recognition responses of six children, aged 7 years and 0 month to 8 years and 9 months, with severe reading disorders. These semantic substitutions occur in the absence of phonological skills. Therefore, it appears that there exists a small subset of developmental dyslexics who at the beginning of acquisition of reading skills are able to engage in semantic processing, but who show severe impairment of phonological processing. The existence of these reading errors indicate that the use of a phonological code is not necessary to extract meaning from the printed word.     

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.