Forty-two single mothers with young infants were given access to a computer-mediated social support (CMSS) network concerned with parenting issues. The network operated 24 hours per day over a period of 6 months. It permitted public message exchanges, private e-mail, and text-based teleconferencing for as many as 8 participants at any one time. During the 6 month intervention, the 42 women accessed the network over 16,670 times. Individual differences in participation were significantly associated with indices of social isolation from peers. A descriptive analyses of the messages exchanged on the network disclosed that 98% of the replies to concerns posted in the public forum provided positive social support. The majority of the supportive replies fell into the category of emotional support, followed in order by informational and tangible support. Both the self-report data following the intervention, and qualitative data extracted from online discussions indicated that close personal relationships and a sense of community developed in this novel social environment. Finally, an analysis of pretest-posttest changes in the level of parenting stress revealed that mothers who participated regularly in this CMSS community were more likely to report a decrease in parenting stress following the intervention.

Attempted to identify the mechanism that underlies the differential outcome effect in acquisition and working memory in pigeons. Different outcomes were cued by 2 pairs of colors that also served as initial stimuli in 2 delayed conditional discriminations. The test stimuli were vertical and horizontal lines. Ss were 22 White Carneaux pigeons. The outcomes were arranged so that expectancies based on them would cue the same response patterns to the 2 test stimuli in both problems (consistent conditions) or opposite response patterns (inconsistent conditions). In Exp I, the 2 problems were trained concurrently; acquisition was faster and reached a higher level in the consistent conditions. In Exp II, transfer of a discrimination between pairs of initial stimuli was studied. Transfer based on consistent expectancies was almost perfect, but there was no transfer with inconsistent expectancies. Shifts from inconsistent to consistent training conditions improved performance, and those in the opposite direction worsened performance. It is concluded that expectancies act as mediating cues and control discriminative behavior directly, strengthening or replacing the cues provided by initial stimuli. (French abstract) (18 ref)

and Summary In ethological studies it is common practice to obtain multiple observations on each individual in a sample and to Pool these observations into one data set for statistical analysis. In this paper we argue that this procedure reflects a fundamental error in the logic underlying random sampling since it implicitly assumes that the purpose of data gathering in ethology is to obtain large “samples of behaviour” rather than samples of behaviour from a large number of individuals. That is, it is assumed that the reliability of estimates of population parameters can be increased by obtaining additional observations on individuals already in the sample rather than by increasing the number of individuals observed. Using a Monte Carlo simulation we show that when such Pooled data sets are analysed statistically, the probability of rejecting a true null hypothesis is almost always substantially greater than the stated alpha level. Zusammenfassung In ethologischen Untersuchungen ist es üblich, von jedem Individuum einer Stichprobe mehrere Meßwerte zu gewinnen und für die statistische Analyse die Werte aller Individuen zu einer einzigen Stichprobe zu vereinigen („pooling”). Diesem Verfahren liegt, wie in der vorliegenden Arbeit gezeigt wird, ein fundamentaler Irrtum bezüglich der zufälligen Stichprobenauswahl zugrunde, da implizit davon ausgegangen wird, man müsse große Stichproben der Verhaltensweisen anstatt Stichproben des Verhaltens möglichst vieler Individuen sammeln. Damit wird angenommen, daß Populationsparameter zuverlässiger geschätzt werden können, wenn man mehr Beobachtungen am bereits in der Stichprobe vertretenen Individuen macht als wenn man zusätzliche Individuen beobachtet. Mit einer Monte–Carlo–Simulation wird gezeigt, daß die statistische Analyse solcher zusammengesetzter („pooled”) Stichproben fast immer eine wesentlich großere als die angegebene Irrtumswahrscheinlichkeit für („type I error”) ergibt.

Four pigeons were trained in a delayed conditional discrimination in which color and line cues jointly indicated trial outcome. These were either combined in advance of a retention interval (RI) or separately presented before and after the RI. The former procedure resulted in less forgetting over the RI, the difference increasing with longer RIs. In a second study, the line cue was presented redundantly before and after the RI, and then selectively omitted from either temporal location during probe tests. In general, the results indicated that the birds relied upon the line as a cue to a greater extent when it was compounded with the color in advance of the RI than when it was presented after the RI. The data support an interpretation based on anticipatory processing in working memory, which leads to better retention than retrospective remembering.Many experiments on "short-term" memory in animals involve a conditional discrimination in which the information required for the correct response on each trial is provided by stimuli which are separated by an interval of time. A simple form of this problem was developed by Nelson and Wasserman (1978). Each trial began with a color as the sample, or initial, stimulus. This was followed by a retention interval (RI), during which no discriminative stimuli were presented. Then a test stimulus was shown. On positive trials, the test stimulus matched the initial color and the trial outcome was food, which was procured by responding to the test stimulus. On negative trials, the test stimulus did not match the initial stimulus, responses to the test stimulus had no effect, and the trial ended with a blackout. Discriminative responding was indicated by the proportion of total responses to the test stimulus on positive trials. Accuracy deteriorated markedly with increases in the RI.With this method, Nelson and Wasserman systematically replicated the "memory decay function" typically obtained with the more familiar form of delayed true or conditional matching, in which two test

Pigeons key pecked for grain on a fixed-ratio 100 schedule; electric shocks occurred intermittently at the fifteenth or eighty-fifth response in the ratio. In Experiment I, shock was at the fifteenth response for two birds, and at the eighty-fifth response for two others, in every sixth, twelfth, or eighteenth ratio. Rate of responding decreased as frequency of shock increased, and the pattern of responding included an increased initial pause and low rates or pause-run sequences that extended further into the ratio when shock was at the fifteenth response than when it was at the eighty-fifth response. Shock early in the ratio engendered longer initial pauses than shock late in the ratio. In Experiment II, four birds responded on a two-component multiple schedule in which shock occurred at the fifteenth response of the third ratio in the presence of a white keylight and at the eighty-fifth response of the third ratio in the presence of a green keylight. The overall rates of responding decreased as shock intensity increased. All four birds responded differentially to the white and green keylights, but with a pattern that varied between birds. In general, punishment reduced the probability of responses that preceded it, regardless of the ordinal position of those responses. Both studies confirm that the probability of responding is reduced less by aversive stimuli produced late in a fixed-ratio than by aversive stimuli produced early in a fixed-ratio.