Eliminative and enumerative behaviour in a conceptual task

P. C. Wason's paper “On the Failure to Eliminate Hypotheses in a Conceptual Task” is criticized on the grounds that the task set is in important respects untypical of problem solving situations in general. It is suggested that few or no subjects are “Eliminators” in Wason's sense and that although many are “Enumerators” in his sense, enumerative behaviour is a function of the situation. An experiment is reported in which it appears that modification to the situation can sharply reduce the incidence of enumerative behaviour and increase the subject's chance of success at an early stage. The frequency with which hypotheses are directly eliminated is shown to be very low in all groups.     

Some errors of perceptual analysis in visual search can be detected and corrected

This experiment tried to discover whether people can correct errors which occur because they incorrectly analyse a display to which they have to respond--whether, in fact, they can correct “perceptual” as well as “motor” errors. In a serial, self-paced visual search task, subjects made one response to indicate that a display of five or nine letters contained either of a pair of target letters, and another response when no target was present. Omission errors were much more common than False Identification Errors, but more of them were corrected. Omission errors were detected and corrected faster than False Identification Errors. Typically omission errors were slow responses while False Identification Errors were fast responses. It is possible to deduce that at least some errors resulting from incorrect analysis of a display can be detected and corrected, probably because of an extension of perceptual analysis during, or immediately after, the time when a response to the display is made.     

Contextual validity and the effects of low-constraint sentence contexts on lexical decisions

Subjects made lexical decisions after reading either (a) low-constraint sentence contexts that did not predict the identity or meaning of congruous targets (e.g. “Mary went to her room to look at her XXXX”), or (b) control contexts that were randomly ordered lists of words. The crucial variable was the validity of the contextual information. When the sentence contexts were incongrous with the word targets as often as they were congruous (the “less-valid environment”), the congruous contexts had a slight inhibitory effect on decision latency relative to the baseline condition. In contrast, when the contexts were always congruous with the word targets (“valid environment”), they had a large facilitatory effect on decision latency. These results suggest that (a) the effects of congruous contexts can depend on the validity of the contexts across the entire experimental session, and (b) contextual facilitation may be due in part to sentence level processes.     

Discriminability and central intermittency in same-different judgements

Four sets of paired visual stimuli (OO, XX, XO, or OX) were judged by 48 subjects to be either “same” or “different.” Decision latencies of the same and different judgement were studied as a function of the inter-stimulus interval (ISI). In Experiments I and II, in which stimulus durations were 70 millisec., decision latencies showed marked increases when the ISI was reduced to 100 millisec., but in Experiments III and IV, in which the stimulus durations were only 40 millisec., comparable increases did not occur until the ISI was reduced to 50 millisec. These increases were more marked for “same” than for “different” judgements, although overall decision latencies were generally shorter for “same” judgements. The effects of varying ISIs and stimulus durations are interpreted in terms of masking; they fail to support an hypothesis of central intermittency.     

Acoustic factors in visual search

Previous work has shown that in searching for existing or absent “e.s” in printed prose, the presence or absence of silent “e.s” was less likely to be detected than that of pronounced “e.s.” It was suggested that the acoustic or kinaesthetic “image” was searched for evidence of an “e” in addition to the visual stimulus and that evidence from both sources was considered in making the appropriate response.

The present experiment employs mainly substitutive errors within words, which may or may not change their pronunciation. The results suggest that the form of the acoustic correlates has no bearing upon whether the words are detected as wrongly spelt, but that the presence or absence of an acoustic event corresponding in time to the spatial location of the error is important.     

A note on further experiments on the effects of meprobamate on discrimination performance in the monkey

A previous experiment (Gross and Weiskrantz, 1961) has shown that performance on a successive auditory discrimination task is impaired by injections of meprobamate. The present two brief experiments indicate that the drug also impairs simultaneous visual discrimination performance, although not to the same degree as found earlier for auditory discrimination. The original finding, therefore, cannot be attributed simply to unique features of the auditory discrimination situation, such as the “go—no-go” response contingency. Since neither overtraining nor drug habituation appears to be of great importance, it is suggested that the lesser effect of the drug in these experiments reflects the greater stability of visual than auditory habits in the monkey.

Earlier work has shown that meprobamate and reserpine can cause a severe deterioration in auditory discrimination performance of monkeys (Gross and Weiskrantz, 1961). This result was taken as supporting a hypothesis, growing out of still earlier research, that tranquillizers decrease the utilization of sensory information (Weiskrantz and Wilson, 1956; Weiskrantz, 1957).

The auditory task, as is almost always the case with monkeys as subjects, involved a “go—no-go” type of response contingency—i.e. the animal had to respond to the positive stimulus and had not to respond to the negative stimulus in order to achieve reward. It might be objected, therefore, that the deterioration in performance was associated not with discrimination as such but with the animals' willingness to perform at all. In fact, it was found that the animals tended to make most of their errors under the drugs by responding when they should not rather than not responding when they should.

The purpose of the present experiments, therefore, was to test the animals with a visual discrimination task in which both the positive and negative stimuli were presented simultaneously. An effect of the drug could not, in this situation, be characterized simply as altering the responsiveness of the animal. A further purpose in using visual stimuli was to test the generality of the earlier finding in a sense modality other than audition.     

Beoadbent's filter theory: Postulate H and the problem of switching time

Groups of digits were presented binaurally and dichotically to subjects who were asked to recall them. Different rates and patterns of presentation were used, the design being based on that of Broadbent (1954). Broadbent's findings in this field were confirmed. If subjects are presented with simultaneous pairs of digits at a rate of 2 pairs per second dichotically, they cannot recall them if they are asked to alternate between the ears. If however the presentation is staggered, so that although the rate is constant the signals do not overlap, subjects can recall alternately from the two ears. It is suggested that these findings are better interpreted as an interference effect, not a rate effect. Criticism is offered of similar designs to measure “switching rate”. Criticism is also offered of Broadbent's estimate of “perception time” in such experiments. An analysis of the quantity and type of errors made by subjects is given, which suggests that Broad-bent's theory of a short term store on the peripheral side of a selective filter is in need of revision.     

Experimental disorientation in the horizontal plane

Twenty-eight subjects were examined on a visual matching task for their ability to maintain an orientation with respect to a particular direction in the horizontal plane following a voluntary rotary body movement through 180 degrees. Each subject was examined with respect to eight different directions.

Numerous gross errors occurred when visual information was reduced to the display of an arrow indicating a direction and a second arrow manipulated by the subject. The magnitude and distribution of the errors suggest that, under the conditions of this experiment, visual information as to direction in the horizontal plane is analysed according to the two horizontal dimensions defined by the sagittal and coronal planes of the head. In correcting for the rotary body movement, failure may occur with respect to either or both of these two dimensions. The frequency of a failure to make any correction at all (i.e. 180-degree errors) is consistent with independent failure in each of the two horizontal dimensions.

Failure is markedly more frequent in the fore-aft dimension than in the left-right dimension. It is suggested that this may be explained in terms of the ambiguous spatial significance of vertical disposition on the retina and the possibility of contamination between the two systems of conceptual analysis which identify the vertical and the fore-aft dimensions of visual space.

It is demonstrated that when minimal “landmarks” are provided they tend to be utilized as reference points in attempts to maintain orientation, even when the subject is aware that the “landmarks” are misleading. Such a use of “landmarks” does not suppress the previously mentioned mechanism of dimensional orientation.

The relevance of these results to normal human orientation is discussed.     

Lowering of an auditory threshold by a near threshold warning signal

Following previous experiments on the effect of suprathreshold “warning” signals in lowering the threshold for stimuli in another modality, we have used visual “warning” signals which are themselves within the threshold range. These near threshold “warnings” appear to act in exactly the same way as suprathreshold “warnings” provided they are seen. Very weak “warnings” have a reduced effect, probably because they are not always seen. The experiment is of interest in that it supports the theory that the effect is due to the “warning” signal reducing the subject's uncertainty about when the threshold stimulus will occur, and secondly because it indicates that under these conditions at least, the subject can attend effectively to two simultaneous near-threshold stimuli.     

Does the autistic child have a metarepresentational deficit?

This study examines the claim that autistic children lack a “theory of mind” because of an inability to metarepresent. We argue that if autistic children have a “metarepresentational” deficit in Leslie's (1987, 1988) sense of the term, then they should have difficulty not only with mental representations such as false beliefs, but also with external representations such as photographs. Autistic children's understanding of photographic representations was tested using Zaitchik's (1990) task. This task is modelled on the false belief task (Baron-Cohen, Leslie, & Frith, 1985: Wimmer & Perner, 1983) but involves “false” photographs where a photographic representation does not conform with the current state of the real world. Like Zaitchik (1990) we found that normal 3 and 4-year-olds found this task as difficult as the false belief task. In sharp contrast, however, the autistic children in our study passed the photograph task but failed the false belief task. As both tasks require the ability to decouple, this evidence challenges the view that autistic children lack “metarepresentational” ability in Leslie's sense. However, the results leave open the question of whether autistic children have a metarepresentational ability in the different sense of the term intended by Pylyshyn (1978), that is, representing the relationship between a representation and what it represents.     

Processing a display even after you make a response to it. How perceptual errors can be corrected

We know that when people make responses which they did not intend they can discover this by monitoring kinaesthetic and visual feedback. It is less clear whether they can also correct perceptual errors which occur when they mistake one signal for another. It was argued that, if they can sometimes do this, extra errors which occur when discriminations become more difficult may be detected and corrected. Experiment I compared the ability of young fit subjects to detect errors made during easy and during difficult discriminations between tone signals. There was no evidence that any additional errors made to difficult discriminations were detected. Fast errors were detected, slower errors were not. The results were consistent with the idea that subjects can detect fast motor errors by monitoring feedback, but that they cannot detect perceptual mistakes.

In Experiment II subjects made easy and difficult line length discriminations. Displays lasted for 100 ms, 200 ms or 500 ms and were followed by random masks. In this case, fast errors were again corrected more frequently than slow errors but eight aspects of the data suggest that subjects could, and did, correct perceptual as well as motor mistakes and that they managed to do this by continuing to process a display after the moment at which they may have initiated an impulsive response to it. The data are interpreted in terms of a “Committee Decision” model for extended perceptual processing previously applied to other, similar data by Rabbitt and Rodgers (1977) and Rabbitt, Cumming and Vyas (1978).     

The development of socialization skills in an electively mute child

In a booth designed especially for work with both autistic and electively mute children, a 4-yr-old girl named Dolly, who had no communicative speech or imitative skills, was given a preliminary session in which her verbal output was assessed. To elicit sounds from Dolly, an instrument called a “color organ” was used as a positive reinforcer. After this baseline assessment, in 40 half-hour sessions, Dolly was taught to make eye contact with E, and to obey instructions—although it was first necessary to extinguish her disruptive behavior, particularly her opérant crying. In addition, she learned non-verbal imitative behavior, such as hand clapping; and verbal imitative behavior, such as saying “Hi!” Social (play) sessions were begun after session 21, and continued for the remaining time. These were helpful in generalizing Dolly's learned skills to an environment other than the booth; and to other tasks, such as singing “Ee-eye-ee-eye-oh” in the refrain of the song, “Old McDonald”; and pointing to E's eyes, saying “ice”.     

Perceptual grouping of speech components differing in fundamental frequency and onset-time

Are there general auditory grouping principles that allow the sounds of a single speaker to be grouped together before phonetic categorisation? Four experiments are reported on the use made of a common fundamental frequency or a common starting time in grouping formants together to form phonetic categories. The first experiment shows that the perception of a vowel category is unaffected by formants being excited at different fundamentals or starting at 100-ms intervals. The second and third experiments show no effect of a different fundamental on the combination of the timbres of pairs of formants presented either binaurally or dichotically to form diphthongs. Onset-time also has no effect with binaural presentation. The fourth experiment finds both an effect of grouping formants by a common fundaental using formant trajectories that do not overlap in frequency, and also an effect of onset-time. Neither a common fundamental nor common onset-time is either a necessary or a sufficient condition for formants to be grouped into a common speech category, although they can be shown to exert an influence. Both these variables exert a considerable influence on the number of sounds that subjects report hearing, even under conditions where they do not influence the reported speech category, indicating a dissociation between mechanisms concerned with “how many” sound sources there are, and those concerned with “what” a source consists of.     

Recognizing melodies: A dynamic interpretation

Two experiments explore hypotheses about rhythm and contour in recognition of simple pitch strings (melodies). Target melodies that differed with respect to pitch relationships (interval and contour pitch differences) and rhythm, were presented to ordinary listeners who were told to learn the melodies (Phase I). In a subsequent recognition test (Phase II), listeners had to recognize these same target melodies although they were transposed to a different musical key. In recognition, target melodies appeared in the original rhythm or in new rhythms that simulated some pause properties of the original rhythm. Target melodies were interspersed with decoy melodies that either preserved the pitch contour of targets or did not; all appeared in the original rhythm and in new rhythms. Results indicated that a new rhythmic context lowered recognizability of target melodies, and that decoys were most confusing when they possessed the same “dynamic shape” (contour-plus-rhythm) as targets (Experiment 1). Also, target recognition improved with Phase I familiarity (Experiment 2), although rhythmic shifts remained detrimental across levels of target familiarity. Confusions based on “dynamic shape” accounted for a relatively high proportion of errors where familiarity with targets is low. Findings were interpreted in terms of a theory of context-sensitive dynamic attending in which remembering is assumed to involve recapitulation of the original rhythmical activities involved in attending to melodies.     

On knowing the meaning of words we are unable to report confirmation of a guessing explanation

This experiment investigated Allport's (1977) claim that normal subjects can be induced to make semantic errors of the type characterised by “deep dyslexia”. The procedure followed that used by Allport except that a subject based control for the chance level of semantic errors was included. The results replicated the original finding by producing a semantic error rate of 12·7%. It was shown, however, that this rate was not significantly higher than the calculated chance rate of 11·5%. It was concluded, therefore, that the semantic error rates reported by Allport can be accounted for in terms of a guessing artefact and thus they bear no relevance to the problem of deep dyslexia.     

Consistency in interpretation of probabilistic phrases

It is occasionally claimed in both applied decision analysis and in basic research that people can better use and understand probabilistic opinions expressed by nonnumerical phrases, such as “unlikely” or “probably,” than by numbers. It is important for practical and theoretical reasons to evaluate this claim. The available literature indicates that there is large variability in the mapping of phrases to numbers, but provides no indication as to its cause. This study asks (a) whether the variability can be attributed to how people interpret the phrases per se, rather than to how they use the number scale and (b) whether the variability is due primarily to between-subject or to within-subject factors. In order to answer these questions, 32 subjects ranked and compared 19 probability phrases on each of three occasions. The results show that individuals have a relatively stable rank ordering of the phrases over time, but that different individuals have different rank orderings. Practical and methodological implications of these data are discussed.     

An in depth, astute, comprehensive, and erudite attempt at categorization of stuttering theorists

The purpose of this paper is to make the reader aware of the various theoretical categories into which people who have been productive in the area of stuttering can be “slotted.” Readers are encouraged to read the characteristics, as I conceive of them, of each group of people and then see where their favorite “authorities” (which in many cases will undoubtedly include themselves) fit.     

A memory-based, Simon-like, spatial congruence effect: Evidence for persisting spatial codes

The Simon effect refers to the finding that in a task where stimulus location is irrelevant, reaction time is faster when stimulus and response locations are congruent than when they are not. Dominant theories of the Simon effect have generally attributed this spatial congruence effect to a spatial code automatically generated upon stimulus presentation. A common assumption of these theories is that this spatial code decays in less than a few hundred milliseconds following stimulus onset. We report two working-memory experiments suggesting a reexamination of this assumption—a Simon-like spatial congruence effect persisted over a delay of as long as 2400 ms. We propose that, in addition to generating short-lived perceptual codes, spatial information may be coded in working memory as part of the context associated with stimulus events. When reactivated by cues from the original event, such information may influence response selection and produce spatial congruence effects (in this case, positive when participants made a “yes” response and negative when they made a “no” response).     

Pseudohomophone Naming and the Word Frequency Effect

An experiment by McCann and Besner (1987) suggested that non-words that are homophonic with a high-frequency word (e.g. “keap”) are named in the same amount of time as non-words that are homophonic with a low-frequency word (e.g. “fome”), despite such pseudohomophones being faster to name than non-pseudohomophones (e.g. “feap”, “yome”). Such a result is a challenge to any model of lexical processing that places the word-frequency effect at the stage when the word is being selected from amongst all lexical entries. McCann and Besner propose a complex alternative account where frequency effects arise at a later stage of processing, a stage that is not involved in the naming of pseudohomophones. The purpose of the present study is to look for a frequency effect in the naming of pseudohomophones, controlling for orthographic factors that McCann and Besner ignored. The first experiment, using a homophone decision task, establishes a set of items that produce a clear frequency effect. These items are then used in a naming experiment which also reveals a clear frequency effect for those subjects who make use of a lexical route when pronouncing pseudohomophones. It is concluded from this that the complex model developed by McCann and Besner is unnecessary.