Daniel W. Smothergill

A two-factor theory of stimulus-repetition effects

It is a well-documented finding that children respond more slowly to a stimulus that has been presented repeatedly just before test than to a novel stimulus. The effect, for which a two-factor theory has recently been proposed, did not occur in the only previous study of adults using a comparable procedure. Experiment 1 demonstrated the effect with adults. The previous negative finding may have been the result of too few repetitions of the stimulus. Experiment 2 provided additional support for the two-factor theory. The theory suggests that the effect is the net result of partially counteracting changes in two attentional processes. One process, the alertness elicited by a stimulus, is held to decrease as a result of repeated presentation of the stimulus, while the second process, encoding, is facilitated. The hypothesis tested in Experiment 2 was that the alertness decrement dissipates over a brief passage of time, while the facilitation of encoding does not. Subjects exposed to a repeatedly presented color were tested either immediately thereafter or after a 15-min or 30-min interval. As predicted, the observed effect shifted from one of flower response to one of faster response to the repeated stimulus as the delay interval increased.

Stimulus Repetition Effects on Attention to Words and Colors.

Mere observation of 30 presentations of a colored form results in slower reaction time responses to the familiarized stimulus than to a comparable novel stimulus. Prior research suggest that this result is due to two subsidiary effects of repetition: alertness decrement and encoding facilitation. Four experiments were conducted to compare the effects of stimulus repetition on colors and words. The two-factor theory of repetition was found to hold for words as well as for colors; for words, in contrast to colors, encoding facilitation was found to be stronger than alertness decrement.

Attention and cognition

Abstract Forty 4-year-old children were subjects in an experimental designed to determine whether learning to attend to relevant cues is a sufficient condition for acquisition of length and number conservation. Three groups of non-conservers were trained by means of an oddity-problem procedure to attend to the cues specifying either length, number, or both length and number. They were subsequently tested along with an untrained control group on tasks of length, number, mass and continuous quantity conservation. Some improvement in conservation was found, but it was neither impressive in magnitude nor specific to the cues of training. For example, the group trained to attend to length cues conserved length about 25% of the time, the same rate at which this group also conserved number, mass, and liquid quantity. This non-specificity is contrary to an attention hypothesis and suggests instead that training, to the extent it was effective, induced a general, abstract quantitative knowledge.

Discrimination and conservation of length

Four-year-olds were Ss in a partial replication of an experiment that had used oddity-problem training to successfully induce conservation of length in 5-year-olds. Training in the present study was successful; a group given knowledge of results on each trial responded to the length cue significantly more often than did an uninformed group. However, neither group evidenced conservation of length on a transfer test. Failure of the present training to induce conservation was predicted by a recent theory of conservation. Hypotheses specifying an identity of processes underlying discrimination and conservation are presented.

Qualitative Change in Word Encoding with Reading Skill.

Abstract Children at different levels of reading skill were studied in four familiarization experiments concerned with word encoding processes. Fifth graders were similar to college students (studied previously) in responding more quickly to familiarized words than novel words. In contrast, first graders with about 1 year of reading experience showed the opposite effect: They responded more slowly to familiarized words. First graders also responded more slowly to novel words belonging to natural taxonomic categories from which other words had been familiarized. This semantic encoding effect is opposite in direction to findings previously obtained in more experienced readers. Overall, these findings provide support for the view that word encoding undergoes qualitative change as reading progresses from beginning to more advanced levels. The reason for this change is unknown.

Effects of temporal relationship between stimuli on children's discrimination learning.

Previous research indicates that temporal relations between discriminanda affect the discrimination process in children. An experiment was conducted to test two hypotheses: (a) simultaneous presentation of stimuli for same-different judgments results in learning the features which differentiate the stimuli; (b) successive presentation facilitates learning a schema of the standard stimulus. A transfer of training paradigm was used with 6- and 7-yr.-old children. Evidence of feature differentiation and schema learning was found; but both kinds of learning occurred under each of the presentation conditions. Procedural differences between this and other studies are noted as possible reasons for the discrepancies in results.

Effects of Stimulus Characteristics on Recognition Memory in Elementary School Children

An exploratory study was conducted to determine how certain stimulus characteristics affect recognition memory in 8- and 9-yr.-old children. 40 Ss were shown 15 letter-like forms for inspection. Later, the original stimuli were shown along with 15 new letter-like forms in a recognition test. Memory was a function of the stimulus characteristics. Prototypes which did not appear on the Inspection series were often responded to incorrectly. It is suggested that these prototypes had been abstracted from transformations of themselves which were present on the Inspection series.

Tests between Two Models of Stimulus Predifferentiation

A stimulus predifferentiation experiment was performed as a test between two models (mediation and differentiation) of discriminative processes. Three groups of preschoolers (n = 51) learned a two-choice simultaneous discrimination between similar line-drawings. Previously, two groups had learned a distinctive name for each drawing and one of them had then repeated the names for 30 sec. Repetition had no effect on discrimination learning, as predicted by the differentiation model but contrary to the mediation model.