The effect on differential eyelid conditioning of 18 h of food deprivation was assessed on New Zealand White and American Dutch rabbits. Food deprivation did not increase the rate of acquisition of the conditioned response, nor did it increase general responsivity. Food deprivation did improve discrimination performance. The Dutch rabbits acquired the CR more rapidly than the albino rabbits and showed a greater responsivity in the conditioning situation. The albino rabbits showed superior discrimination performance.

Machine rule induction was examined on a difficult categorization problem by applying a Holland-style classifier system to a complex letter recognition task. A set of 20,000 unique letter images was generated by randomly distorting pixel images of the 26 uppercase letters from 20 different commercial fonts. The parent fonts represented a full range of character types including script, italic, serif, and Gothic. The features of each of the 20,000 characters were summarized in terms of 16 primitive numerical attributes. Our research focused on machine induction techniques for generating IF-THEN classifiers in which the IF part was a list of values for each of the 16 attributes and the THEN part was the correct category, i.e., one of the 26 letters of the alphabet. We examined the effects of different procedures for encoding attributes, deriving new rules, and apportioning credit among the rules. Binary and Gray-code attribute encodings that required exact matches for rule activation were compared with integer representations that employed fuzzy matching for rule activation. Random and genetic methods for rule creation were compared with instance-based generalization. The strength/specificity method for credit apportionment was compared with a procedure we call “accuracy/utility.“

Computer chess, some years ago, was central to AI research. Today, most of the AI community looks upon computer chess as a misguided child, engaging in activities of dubious scientific value. The present article argues that this common view is incorrect. Computer-chess research represents excellent empirical science and provides a useful model for the AI community. Two decades of computer-chess competition have demonstrated that, for some applications, memory-based reasoning may be superior to a serial reasoning process based on deductive logic.

A series of experiments were conducted to determine what factors control responding to the first element of a two-element serial compound in rabbit eyelid conditioning. An examination of response topography indicated that the eye-blink CR is rigidly timed to occur when the US is expected. This response-system characteristic prevents the occurrence of a CR during the first element of a serial compound or during the second-order CS in second-order conditioning. The comparison of a serial gap procedure with conventional serial and trace conditioning procedures suggested that the associative strength of the first element of a serial CS is not strongly influenced by either a second-order conditioning process or by the variable-reinforcement principle.

Kamin’s three-stage blocking paradigm was investigated in rabbit eyelid conditioning, Two manipulations were examined. A change in the CS-US interval from Stage 1 to Stage 2 did not attenuate blocking. The introduction of a salient stimulus during the intertriai interval in Stage 2 also failed to attenuate blocking. The first result is not consistent with Kamin’s interpretation of the blocking effect in terms of US surprisingness. The second resuit is inconsistent with a prediction based on the Rescorla-Wagner model.

Three properties of the cusp catastrophe: bimodality, inaccessibility, and hysteresis were evaluated in rabbit eyelid conditioning. Bimodality was evidenced by the fact that responding tended to occur at either very low or very high levels, and inaccessibility by the fact that intermediate levels of responding were rarely encountered. Hysteresis was demonstrated when: (a) levels of responding attained under a continuous schedule of reinforcement were largely maintained by a schedule which was too lean to promote conditioning by itself; and (b) levels of responding attained with a high intensity unconditional stimulus were largely maintained by a lower intensity unconditional stimulus which was too weak to promote conditioning in its own right. These results are consistent with the model of conditioning suggested by P. W. Frey and R. J. Sears (Psychological Review, 1978, 85, 321–340) which postulates response-mapping rules based on the cusp catastrophe.

Second-order conditioning has been frequently observed with the fear response but not with the eyelid response. The present experiments manipulated the temporal relationship between the second-order and first-order stimulus on second-order conditioning trials. Our results indicated that a trace second-order procedure is not effective with either response system. Second-order fear conditioning was most prominent when the second-order CS terminated at the onset of the first-order CS. This arrangement, however, did not produce second-order eyelid CRs. In eyelid conditioning, the second-order CS appears to inhibit responding to the first-order CS which immediately follows it.

A manipulation of the instructions students received prior to completing the 7-item Endeavor Instructional Rating card differentially affected their ratings on two types of items. Specifically, when students were led to believe their ratings would have a strong impact on the instructor's career, they tended to be more lenient on items measuring rapport (i.e., the affective domain); this same effect was not observed for items measuring pedagogical skill (i.e., the cognitive domain). The different items on our instructional rating instrument appear to be measuring different things. One implication of this observation is that the inconsistent findings reported in past research on student ratings of instruction may be due to the differential mix of items from one instrument to another. When instructors are compared on ratings given them by students, unbiased interpretation requires that the multidimensional nature of teaching (and of the rating instrument) be considered.

Investigations studying fear in the rat have reported that a CS paired in a backward relationship with the US can acquire excitatory properties. This procedure does not appear to be effective in rabbit eyelid conditioning. The present studies examined Rescorla’s proposal that an excitatory effect might be observed with US-CS pairings in eyelid conditioning if the CS was tested in a second-order conditioning paradigm. The results provided no support for this proposal because second-order eyelid conditioning was just as difficult to demonstrate as was backward eyelid conditioning.

Student ratings of instruction were analyzed in terms of two global factors. One factor, which includes items on advanced planning, presentation clarity, and increased student knowledge, was named “pedagogical skill.” The other factor taps information about class discussion, grading, and the availability of help and was named “rapport.” Ratings on the “skill” factor did not covary with class size or the leniency of the instructor's grading but did correlate with a reasonable external criterion of student learning. Ratings of “rapport” correlated inversely with class size and directly with average class grade and showed only a weak relationship to the external criterion of student learning. The “skill” factor showed more interclass stability than the “rapport” factor. Previous research studies which have examined the reliability and validity of instructional ratings and their relationship to student grades and class size have reported inconsistent findings. These inconsistencies appear to result from an inappropriate unidimensional analysis of ratings which should be examined in terms of two of more separate attitude dimensions.

A series of three eyelid-conditioning experiments with rabbits examined the traditional extinction procedure in which the CS is presented in the absence of US presentations. The first study employed a savings test to demonstrate that the rate of reacquisition is faster after a conventional extinction procedure than after a procedure in which the CS and US have been unpaired. The second experiment indicated that this readiness to respond in reacquisition was related to a carry-over effect from the initial acquisition trials. The third study demonstrated that acquisition and reacquisition are similar when the US is maintained in extinction but not when it is omitted. These results imply that procedures which retain the US during extinction are more effective than the conventional CS-alone extinction procedure in eliminating or inhibiting the associative connection between the CS and the US.

Second-order conditioning was examined using the rabbit eyeblink paradigm and the gerbil CER paradigm. Pavlov’s hypothesis that stimulus overlap on second-order trials produces conditioned inhibition and that nonoverlap leads to second-order conditioning was not confirmed. Our results also revealed that the manner in which first-order and second-order trials are intermixed has an important influence on the properties of the second-order CS. A within-session mixture of first- and second-order trials tended to produce second-order conditioning, and a between-session mixture tended to produce conditioned inhibition. Second-order conditioning was more prominent with the gerbil fear response than with the rabbit eyelid response.

Three experiments employed aversive or positive subcortical electrical stimulation in an unconditional stimulus (US) role in rabbit eyelid conditioning. Conditional response (CR) development to a tonal conditional stimulus (CS) was examined when the intracranial stimulation was combined with a conventional cheek-shock US (Experiment 1) or with a lightflash US (Experiment 2). Our findings were consistent with previus observations that the affective impact of the US is important in the development of an overt motor CR. The complex pattern of our results, however, implies that intracranial stimulation has multiple effects on conditioning and argues against any unidimensional interpretation of these outcomes. Our analysis of CR-contingent intracranial stimulation presentation in Experiment 3 indicated that such stimulation does not act as a Thorndikian reward or punishment in rabbit eyelid conditioning.

A series of three experiments replicated and extended earlier research reported by Chase and Simon (1973), de Groot (1965), and Charness (Note 1). The first experiment demonstrated that the relationship between memory for chess positions and chess skill varies directly with the amount of chess-specific information in the stimulus display. The second experiment employed tachistoscopic displays to incrementally "build" tournament chess positions by meaningful or nonmeaningful chunks and demonstrated that meaningful piece groupings during presentation markedly enhance subsequent recall performance. The third experiment tested memory for one of two positions presented in immediate sequence and demonstrated that explanations based on a limited-capacity short-term memory (Chase & Simon, 1973) are not adequate for explaining performance on this memory task.

The final exam performances of seven sections of introductory calculus were compared with student ratings of the instructors. The ratings were made by a mail survey; half of the students were contacted during the last week of classes and the other half during the first week of the subsequent term. The ratings made at the two different times were not reliably different. Although both sets of ratings correlated positively with final exam performance, the ratings made during the first week of the subsequent quarter showed the stronger relationship. Additional analyses indicated that this positive relationship was not dependent on the student's individual grades. Additional informationNotes on contributorsPeter W. FreyPeter W. Frey is associate professor of psychology, Northwestern University.

Three experiments employing the rabbit eyelid conditioning paradigm examined the effect of a variable-duration rest period on the performance of a partially acquired CR. Conditioning performance improved as a direct monotonic function of the retention interval. Performance after a 24-h rest interval was substantially superior to that observed after a rest interval of several minutes. The third experiment indicated that fatigue factors may be an important factor in producing this incubation effect.