The scientific status of American psychology in 1900.

In 1900, psychologists were attempting to define themselves and searching for their role among both academic and non-academic public. The success of experimental methods served to advance their position as exemplary scientists, although, as the authors argue in this article, other factors were also important. First, the issue of measurement involved many disagreements about the tools needed to measure psychological constructs or even whether psychologists should measure anything at all. Second, the relationship between the brain and psychological constructs enhanced psychology's status for some, whereas others felt that psychologists should stay away from such topics. Parallels with present-day concerns among psychologists are addressed at the end of the article.

Artifactual power curves in forgetting.

Recent studies of the mathematical relationship between time and forgetting suggest that it is a power function rather than an exponential function, a finding that has important theoretical consequences. Through computational analysis and reanalyses of published data, we demonstrate that arithmetic averaging of exponential curves can produce an artifactual power curve, particularly when there are large and systematic differences among the slopes of the component curves. A series of simulations showed that the amount of power artifact is small when the slopes of the component curves are normally or rectangularly distributed and when the performance measure is noise free. However, the simulations also showed that the artifact can be quite large, depending on the shape of the noise distribution and restrictions in the performance range. We conclude that claims concerning the form of memory functions should consider whether the data are likely to contain artifact caused by averaging or by the presence of range-restricted noise.

Need probability affects retention: a direct demonstration.

Recent memory theory has emphasized the concept of need probability--that is, the probability that a given piece of learned information will be tested at some point in the future. It has been proposed that, in real-world situations, need probability declines over time and that the memory-loss rate is calibrated to match the progressive reduction in need probability (J.R. Anderson & Schooler, 1991). The present experiments were designed to examine the influence of the slope of the need-probability curve on the slope of the retention curve. On each of several trials, subjects memorized a list of digits, then retained the digits in memory for 1, 2, 4, 8, or 16 sec. Some trials ended with a recall test; other trials ended with the message, "no test." In Experiment 1, the likelihood of encountering a memory test (i.e., the need probability) was made to either increase or decrease as the retention interval increased; in Experiment 2, need probability either was flat (invariant across retention intervals) or decreased as the retention interval increased. The results indicated that the shape of the need-probability curve influenced the slope of the retention curve (Experiment 1) and that the effect became larger as the experimental session progressed (Experiment 2). The findings support the notion that memory adapts to need probabilities and that the rate of forgetting is influenced by the slope of the need-probability curve. In addition, all of the forgetting curves approximated a power function, suggesting that need probability influences the slope but not the form of forgetting.

Processing of formational, semantic, and iconic information in American sign language.

Three experiments examined short-term encoding processes of deaf signers for different aspects of signs from American Sign Language. Experiment 1 compared short-term memory for lists of formationally similar signs with memory for matched lists of random signs. Just as acoustic similarity of words interferes with short-term memory or word sequences, formational similarity of signs had a marked debilitating effect on the ordered recall of sequences of signs. Experiment 2 evaluated the effects of the semantic similarity of the signs on short-term memory: Semantic similarity had no significant effect on short-term ordered recall of sequences of signs. Experiment 3 studied the role that the iconic (representational) value of signs played in short-term memory. Iconicity also had no reliable effect on short-term recall. These results provide support for the position that deaf signers code signs from American Sign Language at one level in terms of linguistically significant formational parameters. The semantic and iconic information of signs, however, seems to have little effect on short-term memory.

Intelligibility and comprehension of time compressed sign language narratives.

A method of time compressing visual displays was devised to assess the effects of compression on the comprehension of American sign language (ASL). Two ASL narratives were visually presented to three groups of deaf ASL users. A compression group was presented narratives compressed to 50% of the duration of the normal rates. A no-compression group was presented narratives signed at normal rates. A pause groups was presented compressed narratives with blank pauses inserted so that the total time per narrative was equal to that of the no-compression versions. Following each narrative, subjects completed a written comprehension task. Comprehension in both compression and pause groups was significantly lower than in the no-compression group. Pauses did not significantly affect scores relative to compression. An additional group of deaf ASL users was presented an intelligibility task in which signs taken from the narratives were presented in isolation either with or without compression. The total number of signs correctly identified was significantly lower with compression. Decrements in comprehension were best explained as the result of cumulative decrements in sign intelligibility and not as the result of decrements in available processing time.

Semantic organization in deaf and hearing subjects.

Hierarchial cluster analysis of data from the sorting of noun words was used to compare semantic structures in 63 profoundly deaf and 63 hearing adolescents. In the first study, performance differed only for a set of words referring to sounds, where deaf persons have no experience, and not for a set of common noun words and pictures. In the second study, differences between matched sets of high- and low-imaginary words were comparable for 63 deaf and 63 hearing subjects. It is concluded that deaf subjects manifested abstract hierarchical relations and were not dependent on "visual mediators" or hindered by the absence of "acoustic mediators".