Infant sensitivity to figural coherence in biomechanical motions

Two experiments assessed infant sensitivity to figural coherence in point-light displays moving as if attached to the major joints of a walking person. Experiment 1 tested whether 3- and 5-month-old infants could discriminate between upright and inverted versions of the walker in both moving and static displays. Using an infant-control habituation paradigm, it was found that both ages discriminated the moving but not the static displays. Experiment 2 was designed to clarify whether or not structural invariants were extracted from these displays. The results revealed that (1) moving point-light displays with equivalent motions but different topographic relations were discriminated while (2) static versions were not, and (3) arrays that varied in the amount of motion present in different portions of the display were also not discriminated. These results are interpreted as indicating that young infants are sensitive to figural coherence in displays of biomechanical motion.     

More precisely defining and measuring the order-irrelevance principle

R. Gelman and C. Gallistel (1978, Young Children's Understanding of Number, Cambridge, MA: Harvard Univ. Press) use two definitions of the order-irrelevance principle interchangeably: (1) count tags do not have to be assigned in a fixed order and (2) the order in which elements of a set are enumerated does not affect the cardinal designation of the set. A study involving 107 kindergarten and first grade children indicates that the two are actually distinct concepts. Apparently, a willingness to arbitrarily assign tags is a developmentally less sophisticated ability than--and hence does not necessarily imply--an ability to predict that differently ordered counts produce the same cardinal designation. Thus it appears that evidence of the second ability is necessary to infer a full understanding of the order-irrelevance principle. The first ability alone implies what might better be termed an "order-indifferent tagging scheme." Suggestions for measuring and further researching the order-irrelevance principle are discussed.     

The selective impact of question form and input mode on the symbolic distance effect in children

Five experiments are reported on the symbolic distance effect (SDE) and related phenomena with 6- and 9-year-old children. In the first of these, children were asked to judge the relative sizes of animals in verbal and pictorial tests featuring the comparatives "bigger" and "smaller." A perceptual condition with actual objects was included by way of comparison. A Symbolic Distance Effect was obtained for both lexical and pictorial input. Mode differences were also observed. Pictures produced faster responses than words, and congruity effects occurred only in the pictorial condition. Although performance was similar in tests with either comparative, our subsequent experiments on both 6- and 9-year-olds reveal a significant asymmetry in the child's capacity to verify statements of relation as a function of the direction along the (size) continuum implied by the question. However, important differences between age groups also apparent in the data lead us to conclude that the older subjects develop strategies to overcome this asymmetry by translating certain statements of relation into a form more congruent with their natural modes of encoding.     

Selective association learning in the rat: Generality of response system

Three experiments with rats examined the possibility that the cue-consequence specificity effect is not mediated by the conditioning of selective associations, but instead reflects the selective behavioral expression of taste-illness and exteroceptive-shock conditioning. Experiment 1 showed that the selective aversion performance could be obtained despite the use of locomotor withdrawal from the CS as the index of conditioning. Experiment 2 compared the response profiles of animals conditioned with footshock or illness to presentation of a saccharin or noise CS. During the test with the noise CS, lithium-conditioned subjects did not differ from control rats on any of several behavioral categories, but shock-conditioned rats showed high levels of freezing in response to the noise cue. During the saccharin test, lithium-treated rats engaged in behaviors such as chin wiping, head shaking, and gaping; these behaviors were rarely or never seen in shock-conditioned rats or controls, whose behavioral profiles during the saccharin test were almost identical. Experiment 3, using a blocking design, found that a noise-lithium pairing did not attenuate subsequent conditioning of a saline-lithium association, nor did a saccharin-shock pairing interfere with conditioning of a noise-shock association. These results confirm that the cue-consequence specificity effect is mediated by the selective associability of taste with illness and of exteroceptive cues with footshock.     

Mechanisms of blocking by contextual stimuli

The influence of contextual stimuli on the conditioning and performance of responding to a discrete stimulus was examined in the US preexposure paradigm using both context shift manipulations and a measure of context conditioning. Four groups of rats received both repeated exposure to an electric shock US in one context (Context 1), and repeated nonshocked exposure to a second context (Context 2). Two additional groups of rats received exposure to these contexts, but never received shock presentations. Rats exposed to shock learned to escape from the stimuli of Context 1, but did not escape from the stimuli provided by Context 2. Rats not exposed to shock failed to escape from either context. All rats then received a single CER conditioning session in which four pairings of a 3-min noise CS and shock US were presented. Half the rats received those CS-US pairings in the excitatory Context 1, while the remaining rats received those pairings in the neutral Context 2. Finally, half the rats in each of the CER conditioning treatments received extinction test trials of the noise CS in Context 1, while the remaining rats received those test trials in Context 2. Thus, this design factorially manipulated the presence of excitatory or neutral contextual stimuli during both conditioning and testing of a discrete CS. In comparison with the two groups of rats never preexposed to shock alone, attenuation in acquisition of conditioned suppression observed during test trials occurred only when CER conditioning had been administered in the excitatory Context 1, and this effect was manifested when testing occurred in either the excitatory Context 1 or the neutral Context 2. These results support the model of R. A. Rescorla and A. R. Wagner (1972) (in A. H. Black & W. F. Prokasy (Eds.) Classical Conditioning II, pp. 64–99, New York: Appleton-Century-Crofts) which asserts that contextual stimuli and sicrete CSs compete for limited associative strength supportable by a given US.     

Variations in explicitly unpaired training are differentially effective in producing conditioned inhibition

To evaluate a contingency interpretation of conditioned inhibition (CI), rats were given “explicity unpaired” training in which the locus and duration of a CS within the inter-US (shock) interval were systematically manipulated for different groups. Summation and retardation tests in Experiment 1 indicated that stronger CI resulted from both a backward and a trace CS than from a midlocus CS of equal or greater duration. Complementing these findings, the same tests in Experiment 2 showed that, by comparison with novel-stimulus controls, CI developed to a trace CS but not to a mid-locus CS, nor to a trace CS that was accompanied by an immediate signal for the US. These findings argue against a contingency interpretation of CI and favor a contiguity interpretation stressing the short-term rehearsal of stimulus events. Such rehearsal of the US allows a backward CS, but not a mid-locus CS with an extended US-CS interval, to be discriminated as a signal for nonreinforcement, and thus to develop as a conditioned inhibitor. Similarly, excitatory conditioning to the memory trace of a CS allows the nominal trace CS to develop as a signal for nonreinforcement, and thus as a conditioned inhibitor, but not when its memory trace is overshadowed by another CS that immediately precedes the US. In short, the development of CI is facilitated when excitation is mediated by the memorial processing of either the US or a discrete CS for the US rather than by contextual cues.     

Youth Testimony at the Opening Prayer of the 11th Assembly of the World Council of Churches

This is the text of the youth testimony at the opening prayer of the 11th Assembly of the World Council of Churches on 31 August 2022.     

Message from the Ecumenical Youth Gathering

This is the message of the Ecumenical Youth Gathering held in advance of the 11th Assembly of the World Council of Churches, which met in Karlsruhe, Germany, in August–September 2022. In their message, the youth voiced a series of laments, and recognized and prayed for justice, forgiveness, and reconciliation of the wounds the church has inflicted and continues to inflict in the world, and they called on the WCC to provide a meaningful space for an equal representation of young people in all its processes.     

HIV and the obligation to treat

The paper is an attempt to review the basis for the claim that physicians have a professional obligation to treat AIDS patients. Considered are the historical record, two professional codes of ethics, and several recent articles. The paper concludes that the arguments considered, which attempt to support the claim that physicians have an obligation to treat, fail. It is suggested, rather, that common humanity, which physicians share with those who suffer from AIDS, ought to be the basis for engaging in the care of AIDS patients.