Auditory discrimination: role of time and intensity in the precedence effect.

Rats were trained to respond on a lever adjacent to a sounding speaker (the sound source) when a single click was emitted. A second click (the artificial echo) was presented through a second speaker on the opposite side. In Condition I, the echo (equal in intensity to the source) was delayed from .015 to 32 milliseconds; greater than 75% correct responses were given for delay times between about .040 milliseconds (lower threshold) and 8 milliseconds (upper threshold). In Condition II, the echo (simultaneous with the source) was reduced in intensity relative to the source over a range from 2.5 decibels to 40 decibels; greater than 75% correct responses occurred for intensity reductions greater than 5 decibels. In Condition III, both the intensity and the delay time of the echo were manipulated in a manner analogous to that which would occur under natural conditions; greater than 95% correct responses were given for delay times from 1 to 32 milliseconds. These data indicate that both time and intensity differences are necessary for localization of primary sources, with delay time contributing more at short echo path distances, and intensity differences at long distances.     

Attention in the pigeon: testing for excitatory and inhibitory control by the weak elements.

In two experiments, pigeons were trained on a successive discrimination between a color and either a compound S+ or a compound S- consisting of a form superimposed on a second color. Two stimulus control tests followed discrimination training: an attention test in which the form and colors used in training were presented singly and in combination, and then a resistance-to-reinforcement test using the form element of S+ or S- and a novel form. In the attention test, the birds trained with a compound S+ responded most to the S+ compound, less to the S+ color alone, and still less to the S+ form on a dark key. Few responses were made to the negative stimulus, either alone or with the S+ form added. The birds trained with a compound S- pecked most at the S+ color and to a compound of the S+ color with the S- form added. The resistance-to-reinforcement test showed that the birds trained with a compound S+ responded more to the S+ form than to a novel form. However, the birds trained with a compound S- did not reliably respond more to a novel form than to the S- form. These findings suggested that the form element of a compound S+ gains some excitatory control, but the form element of a compound S- does not acquire inhibitory control. The possibility existed that low levels of responding to the S+ form on a dark background in the first experiment were due to use of a darkened key to separate S+ and S- periods during discrimination training. However, the essential findings were the same in a second experiment in which darkening of the chamber separated S+ and S- periods.     

Visual dominance in the pigeon

In Experiment 1, three pigeons were trained to obtain grain by depressing one foot treadle in the presence of a 746-Hertz tone stimulus and by depressing a second foot treadle in the presence of a red light stimulus. Intertrial stimuli included white light and the absence of tone. The latencies to respond on auditory element trials were as fast, or faster, than on visual element trials, but pigeons always responded on the visual treadle when presented with a compound stimulus composed of the auditory and visual elements. In Experiment 2, pigeons were trained on the auditory-visual discrimination task using as trial stimuli increases in the intensity of auditory or visual intertrial stimuli. Again, pigeons showed visual dominance on subsequent compound stimulus test trials. In Experiment 3, on compound test trials, the onset of the visual stimulus was delayed relative to the onset of the auditory stimulus. Visual treadle responses generally occurred with delay intervals of less than 500 milliseconds, and auditory treadle responses generally occurred with delay intervals of greater than 500 milliseconds. The results are discussed in terms of Posner, Nissen, and Klein's (1976) theory of visual dominance in humans.     

Repeated acquisition of conditional discriminations

A new technique was developed to study the repeated acquisition of conditional discriminations. Using a discrete trial procedure, pigeons were required to learn during each session a different two-member chain of conditional discriminations. Key color and geometric forms were used as stimuli. After the pigeons had reached a steady state of relearning (40 to 60 sessions), the technique was used to investigate variables that have previously been shown to affect the repeated acquisition of response sequences. Various (0 to 90 seconds) durations of timeout for errors were investigated in Experiment I. The stimulus change associated with a timeout, rather than its duration, was found to be the critical variable in acquisition of the discrimination. Extended training on a single chain was found to reduce total errors across sessions in Experiment II. Extended training (three sessions) did not, however, change the pattern of within-session error reduction. In some cases, extended training facilitated acquisition of a partially reversed discrimination. In Experiment III, color rather than chain position was found to control behavior, for three of the four birds, as the second stimulus dimension in the conditional situation. The results of these experiments replicate and extend previous findings concerning some of the variables that affect the repeated acquisition of response sequences.     

西方社会心理学关于群际行为的研究述评

对西方社会心理学就群际行为这种重要的社会行为所开展的研究,主要包括心理动力学取向的研究、相对性匮乏理论及其研究、现实利益冲突理论及其研究、社会同一性理论及其研究的研究成果,进行了系统的介绍和评价．     

乙肝歧视现象的问题与反思

我国乙肝病毒携带者群体在升学、就业、婚姻等方面遭受着社会歧视.分析乙肝歧视的社会成因,并就如何消除乙肝歧视和促进社会平等提出若干对策.     

Major world events and discrimination

It is known that a major world event caused by one group can influence perceptions of other social groups. The impact of the events of September 11, 2001 on religious and ethnic discrimination in the UK was assessed. Of seven ethnic groups, Pakistanis and Bangladeshis, who were primarily Muslim, reported the greatest increase between pre- and postevent discrimination. So, the attacks on the USA by al-Qaeda, a radical Islamic organization, activated discrimination against people of Islamic faith in the UK. These results highlight links between world events and intergroup relations, and may serve to remind norm violators that the harm they do to people of other groups can impact people of groups perceived to share their values, even in geographically distant places.     

Infant sensitivity to distributional information can affect phonetic discrimination.

For nearly two decades it has been known that infants' perception of speech sounds is affected by native language input during the first year of life. However, definitive evidence of a mechanism to explain these developmental changes in speech perception has remained elusive. The present study provides the first evidence for such a mechanism, showing that the statistical distribution of phonetic variation in the speech signal influences whether 6- and 8-month-old infants discriminate a pair of speech sounds. We familiarized infants with speech sounds from a phonetic continuum, exhibiting either a bimodal or unimodal frequency distribution. During the test phase, only infants in the bimodal condition discriminated tokens from the endpoints of the continuum. These results demonstrate that infants are sensitive to the statistical distribution of speech sounds in the input language, and that this sensitivity influences speech perception.     

辨别任务中线索有效性对儿童返回抑制发展的影响

采用辨别任务范式,运用三个3×3×3的混合实验设计(线索有效性、年级、靶子出现位置),考察了3种线索-靶子时间间隔下线索有效性对辨别任务中儿童返回抑制发展的影响。结果表明:(1)随着年龄的增长,儿童完成任务所需的反应时逐渐缩短;(2)随着年龄的增长,儿童出现返回抑制所需的SOA缩短;(3)辨别任务的难度比较大,所需的认知技能和工作记忆更多,因此返回抑制出现的机制也就更复杂,线索有效性对辨别任务下的返回抑制的影响并没有呈现出规律性的变化。