Disconfirmation and dual hypotheses on a more difficult version of wason's 2-4-6 task

This paper reports two experiments in which subjects worked to solve a more difficult version of Wason's 2-4-6 task: instead of the usual “numbers must ascend in order of magnitude” rule, a more general rule, “the three numbers must be different”, was used. The first experiment established that instructing subjects to disconfirm on the “three different numbers” did not significantly improve their performance, as compared with confirmatory and control groups. Disconfirmatory subjects did try to propose more triples at variance with their hypotheses but were unable to obtain the necessary disconfirmatory information.

To help subjects represent the task in a way that facilitated disconfirmation, the second experiment utilized a procedure in which subjects were told that they were looking for two rules, Dax and Med-the Dax rule corresponding to “three different numbers” and the Med rule to its complement, i.e. two or more numbers the same. Of subjects in the Dax-Med condition, 88% solve the rule, as opposed to 21% of subjects in a control condition. Dax-Med subjects tended to search for positive instances of the Med rule, which, in turn, forced them to test the limits of the Dax rule. It was concluded that the Dax-Med manipulation did facilitate a different mental representation of the task than the normal procedure.     

Inducing a Rule in Wason's 2-4-6 Task: A Test of the Information-Quantity and Goal-Complementarity Hypotheses

In the standard 2-4-6 induction task, subjects are instructed to discover the rule generating sequences of three numbers by inventing number triples for which they receive immediate feedback. The rule is “ascending numbers”. Performance is greatly aided with Dual Goal (DG) instructions that ask subjects to discover two rules, one that generates “Dax” triples (equivalent to “yes” instances with Single Goal [SG] instructions) and another that generates “Med” triples (equivalent to “no” instances). The present study eliminates two explanations for this effect suggested by Wharton, Cheng, and Wickens (1993). Experiment 1 tested their Information-Quantity hypothesis that the effect results simply from the DG subjects testing more triples prior to proposing a rule. Our DG subjects were more likely to solve the problem and produced more “negative” triples than SG subjects when both groups generated exactly 15 triples. Two further groups received feedback only after generating all 15 triples, and again DG subjects were more likely to solve the problem and to generate more “negative” triples. Experiment 2 tested Wharton et al.'s Goal-Complementarity hypothesis that success under DG instructions hinges on preserving the complementary representation of the two rules. We compared SG instructions with three types of DG instructions that suggested different types of triples (Dax, Med, both Dax and Med, neither Dax nor Med). DG instructions were more effective in promoting successful rule discovery regardless of differences in rule complementarity. Our analysis of the heterogeneity of the examplars generated with DG instructions in both experiments suggest that success on the 2-4-6 task is as much a consequence of the breadth of hypotheses that subjects entertain as it is a consequence of the testing strategy.     

A comparison of disconfirmatory, confirmatory and control strategies on Wason's 2-4-6 task

Attempts to instruct subjects to falsify on inference tasks designed to model scientific problem-solving have indicated that, in most cases, falsification does not lead to improved performance. The only study in which instructions to falsify did improve performance was done with groups, using a novel inference task. The present study is an attempt to replicate the success of falsification in the group study with subjects run individually on an inference task that has been used extensively in the literature: Wason's 2-4-6 problem. Each subject was run in one of three strategy conditions: confirmatory, disconfirmatory or control (no-strategy).

Results indicated that subjects in the disconfirmatory condition solved the 2-4-6 problem significantly more often than subjects in other conditions. The superior performance of disconfirmatory subjects was explained by the fact that they deliberately sought and obtained significantly more falsificatory information than subjects in other conditions.

The critical difference between this study and previous attempts to instruct individual subjects to falsify on the 2-4-6 task is that subjects in the present study were given no feedback as to whether their guesses were right or wrong until the experiment was over. The implications of this result for scientific problem-solving are discussed.     

Skill in map reading and memory for maps

Studies of expertise have typically shown that experts have better memory for materials from their fields than do novices. However, previous research on memory for maps has not shown the expected effect of expertise. The present study differed from previous studies by using contour maps as well as planimetric maps. In Experiment 1 the expected superiority in memory performance was found for skilled map readers when contour maps were used, but not when planimetric maps were used.

In Experiment 2, the main results of Experiment 1 were replicated, and, in addition, process tracing data were obtained during both study and test phases of contour map learning. Objective measures of attentional and retrieval focussing revealed almost no differences between the skilled and unskilled subjects. However, analyses of verbal protocols showed that the skilled subjects made more use of specialist schemata, whereas the unskilled subjects spent more time in reading place names. During recall, the skilled subjects made more use of both specialist and “lay” schemata, whereas the unskilled retrieved more place-name information.

The results are interpreted in terms of a schema-based approach to expertise.     

Matching and oddity learning in the pigeon: Transfer effects and the absence of relational learning

Three experiments examined the extent to which pigeons trained on a matching or oddity discrimination with one pair of colours showed transfer when tested on a new matching or oddity discrimination with a new pair of colours. Experiment 1 examined the effects of key spacing and a delay procedure and replicated previous reports that in the transfer stage subjects given the same kind of problem (Non-shift condition) in general learn more rapidly than those given the opposite problem (Shift condition). However, this difference appeared only when pigeons given matching in both training and transfer stages were compared to those shifted from oddity to matching; it did not appear in birds transferred to oddity. Transfer was not significantly affected by key spacing or by the delay.

Experiments 2 and 3 examined transfer from a non-relational conditional discrimination based on one set of colours to a subsequent matching or oddity task based on two new colours. Both a comparison between the results of Experiment 1 and 2 and the corresponding within-experiment comparison from Experiment 3 showed that transfer from conditional training to matching was as great as from prior training on matching, while prior training on oddity produced negative transfer on shift to matching. It was suggested that this negative transfer occurs because pigeons trained on oddity have not learned to override an initial bias towards the odd stimulus in an array. Whatever the correct explanation; the present results provide no support for the claim that pigeons solve matching or oddity discriminations relationally.     

The locus of maximum weighting within attentive fields: An empirical investigation

Fixation within a modified Poggendorff display was used to assess Pressey's hypothesized construct of attentive fields. In Experiment I the results for fixating near the bottom of the display supported the predictions based on Pressey's construct; however, results from fixating near the top of the display were more easily explained by a tilt effect noted by Zajac (1957).

Experiment II and III replicated the first experiment and obtained independent measures of the tilt effect. After the tilt effect was subtracted from the Poggendorff scores, the prediction based upon the attentive field construct was supported in the top fixation condition; however, only Experiment II provided support for the prediction in the bottom fixation condition.     

Graphical representation fosters discovery in the 2-4-6 task

In the 2-4-6 rule discovery task, reasoners seek to discover a rule that governs the arrangement of three numbers (or triple). The to-be-discovered rule is “ascending numbers”. Upon being given the triple 2-4-6 as an initial example, however, reasoners tend to formulate algebraically specific hypotheses. Traditionally, this task is conducted primarily from an internal representation of the triples and candidate hypotheses. More recently, substantial representational effects have been demonstrated wherein an external representation of the dimensions of the problem space facilitated successful rule discovery. In the two experiments reported here, an interactive graphical representation was created by concurrently plotting each triple produced by the participants. In Experiment 1, participants who performed the task with this external representation were more likely to discover the rule than were a group of control participants. Experiment 2 replicated the effect but also assessed participants' hypotheses for each triple generated. Results indicated that a graphical representation of the triples fostered the development of hypotheses that were less constrained by the implied algebraic specificity of the initial triple.     

Acquisition and extinction of a simple motor skill as a function of delay of knowledge of results

The present experiment demonstrates that the effects of delay of knowledge of results (KR) in a line drawing task depend upon the dependent variable which is considered and the original response tendency of the subjects. Delay of KR interfered with the acquisition of the correct response when number of correct responses is the dependent variable. When KR was omitted the immediate-KR group continued to make more correct responses than the delayed-KR group. However, there was a significant reduction in correct responses for both groups. When absolute error was the response measure there were no significant differences between immediate-and delayed-KR groups either during acquisition or extinction. Analysis of the type of response made during extinction suggested that the overshooting effect obtained by previous investigators may be typical of short responders trained under conditions of immediate reinforcement but not of those trained under delayed-KR.

Greenspoon and Foreman (1956) obtained clear cut evidence that the effectiveness of knowledge of results (KR) in a line drawing task varies inversely with the time delay between the response and KR. On the other hand, Bilodeau and Bilodeau (1958) were unable to demonstrate a similar effect in five different experiments. Bilodeau and Ryan (1960) hypothesized that the Greenspoon and Foreman findings could not be replicated and they did in fact obtain null results. However, Dyal (1965) has recently replicated the Greenspoon and Foreman results for the case of a 30 sec. delay interval.

The purpose of the present experiment is twofold: (a) to provide replication of Green-spoon and Foreman's study at the 20 sec. delay interval used by Bilodeau and Ryan, and (b) to determine the effect of elimination of KR on a simple motor response which has been formed on the basis of KR.     

Reading for meaning: The effects of concurrent articulation

Six experiments are reported which examine the assertion that phonological recoding for the purpose of lexical access in visual word recognition is prevented or impaired by concurrent articulation (“articulatory suppression”). The first section of this paper selectively reviews the literature, and reports two experiments which fail to replicate previous work.

The third experiment contrasts performance with visually presented words and with non-words. Latency measures show an effect of suppression that is specific to words, whilst error rates show an effect common to both words and non-words. The fourth experiment shows that if the task is changed from a judgement of rhyme (BLAME-FLAME) to one of homophony (AIL-ALE), the suppression effect seen in the latency data is eliminated, whilst error effects remain. It is suggested that, in addition to producing error effects that are not easily interpretable, suppression prevents or impairs a phonological segmentation process operating subsequent to the retrieval of whole word phonology (a process that is needed for rhyme judgement but not for one of homophony).

Experiment V shows that while suppression has no effect on the time taken to decide if printed non-words sound like real words (e.g. PALLIS), error rates increase. Experiment VI shows that suppression has no effect on either RT or errors in the same task if subjects suppress at a slower rate than in Experiment V.

It is suggested that there are at least two different phonological codes. Buffer storage and/or maintenance of phonologically coded information derived from print is affected by suppression; phonological recoding from print for the purpose of lexical access can be carried out without any interference from suppression.     

Visual factors in auditory localization

Previous experiments showing the importance of visual factors in auditory localization are shown to have been insufficiently quantitative.

In the first Experiment, bells were rung and lights shone on the same or different vectors, eleven subjects indicating which bell had rung. In the second Experiment, a puff of steam was seen to issue from a kettle whistle with no whistling sound, while similar whistles were sounded by compressed air on that or another vector. Twenty-one subjects cooperated.

The addition of a visual stimulus at 0° deviation increased the percentage of correct responses significantly in the second, and insignificantly in the first experiment. At 20°-30° deviation the proportion of naive responses to the visual cue was 43 per cent. in the first and 97 per cent, in the second experiment. At greater angular deviations, the proportion of naive responses fell to chance level in the first, but remained significant in the second experiment, even at 90°. The “visuo-auditory threshold” was found to be 20°-30°, but might be much larger if there were more grounds for supposing the two stimuli to be from the same source in space.     

Visuo-spatial processing in working memory

This paper reports four experiments designed to develop a simple technique for the study of visuo-spatial processing within the working memory framework (Baddeley and Hitch, 1974). Experiment 1 involved the matching of successively presented random matrix patterns, as a secondary visual suppression task. This was coupled with rote rehearsal or a visual imagery mnemonic for learning lists of concrete words presented auditorily. Although memory performance with matching dropped overall, the visual mnemonic was differentially affected. Experiment 2 removed the matching decision, with visual presentation of unattended patterns. There was no overall effect of the unattended material, but use of the visual mnemonic was significantly affected. Experiment 3 replicated this result with simpler plain coloured squares as the unattended material.

In Experiment 4, for one group, the unattended material consisted of line drawings of common objects. For a second group, the lists of words for recall were presented visually, with or without unattended speech. The results suggested that unattended pictures disrupt use of a visual mnemonic, while unattended speech disrupts rote rehearsal.

These results suggest that unattended visual material has privileged access to the mechanism(s) involved in short-term visuo-spatial processing and storage. They also suggest that use of a concurrent visual matching task or of unattended visual material may provide tractable techniques for investigating this aspect of cognitive function within the context of working memory.     

Visual search without eye movement

Two experiments have been made on the problem of visual search using six patterns which were geometrically simple, and familiar to the subject.

In each case the subject's task was to say where, among the complex of patterns, a particular pattern (the “test object”) appeared when the exposure of the whole display was so brief as to prevent scanning by the eyes. He could be informed visually (in Experiment I) or verbally (in Experiment II) which pattern was to be regarded as the “test object.”

In both experiments it was found that foreknowledge of what was to be the test object gave a significantly higher standard of accuracy than knowledge given later. This suggests that something analogous to visual search can occur without eye movements.     

Short term retention of sentences

A series of experiments was performed on the interaction between the short-term retention of sentences and of digits. In Experiment I a digit span method was used whereby subjects were presented with a sentence followed by a sequence of digits and were required either (a) to recall the sentence first and then the digits or (b) to recall the digits followed by the sentence. Under condition (a) prior recall of the sentence reduced the percentage of digit sequences correctly recalled, while under condition (b) retention of the sentence appeared to have no effect on digit recall. This last finding was confirmed in Experiment II, where the sentences varied both in grammatical complexity and length.

In Experiment III the effect of prior recall of a sentence on the recall of digits was found to depend on the type of sentence used. A correlation was observed between the size of this effect and the time taken to recall a sentence. The rate of forgetting suggested by this observation was comparable to that obtained in Experiment IV, where subjects performed an intervening task that did not involve immediate memory for sentences in the interval between the presentation and recall of a six-digit sequence.

It was concluded from these results that the short-term retention of sentences and of lists of items cannot be explained in terms of some general store of limited capacity.     

Contextual conditional discriminations

Three experiments used a discriminated operant procedure to study conditional discrimination learning in rats. The first experiment showed that rats were capable of learning a biconditional discrimination in which two contexts served as conditional cues signalling the reinforcement contingencies associated with two discriminative stimuli. The discrimination was learned equally well when one discriminative stimulus signalled food, the other its absence, and when one stimulus signalled food, the other extinction plus mild footshock.

In Experiment 2 it was shown that prior training on such a conditional discrimination enhanced the subsequent context specificity of simple conditioning relative to control groups of animals for whom the prior training had not been conditional. Experiment 3 showed that a reversal of the significance of one pair of discriminative stimuli produced no spontaneous reversal in performance to a second, target, pair.

The pattern of results is best accounted for by an analysis of contextual conditional discrimination learning in terms of stimulus configurations and offers no support for the notion that rats may learn a general conditional rule or set.     

Redundancy effects in short-term memory

Five experiments are reported whose purpose was to demonstrate that short-term memory is improved by redundancy within the material. In Experiment I “tune” containing two, three, four and five tones of differing frequencies had to be coded into digits 1-5, to indicate the order of the pitches in a tune. Performance on stimuli containing correlated amplitude and duration were compared with the uni-dimensional condition. Experiment II repeated I, but required intensity to be coded. Experiment III required pitch coding under three conditions including that when amplitude and frequency were uncorrelated, and compared the performance of musically trained sunjects with nonmusicians. Experiment IV repeated III, but subjects were informed of the relation between dimensions. Experiment V involved “shadowing” the tunes by whistling simultaneously with the stimulus.

It was concluded (a) that intercorrelation improves, but zero correlation impairs short-term memory; (b) that knowledge of the relation between dimensions improves performance in the correlated condition, but does not prevent impairment under zero correlation; and (c) the performance of musically trained subjects exceeds that of controls and is unaffected by the presence of a correlated or uncorrelated dimension.     

The effect of semantic distance in yes/no and go/no-go semantic categorization tasks

The effect of semantic distance (Lund & Burgess, 1996) was examined in three semantic categorization experiments. Experiment 1, a yes/no task that required participants to make animal/nonanimal judgments by responding to both sets of stimuli (Forster & Shen, 1996), revealed no effect of semantic distance. Experiment 2, a go/no-go task that required participants to respond to only the experimental (i.e., nonanimal) items, revealed a large effect of semantic distance. In addition, response latencies were longer and error rates were lower to the experimental items in Experiment 2 than to those in Experiment 1. These findings were replicated in Experiment 3, in which semantic distance and task condition were manipulated within subjects. We conclude that these results are consistent with (1) the view that the go/no-go tasks elicited more extensive processing of the experimental items and (2) a connectionist account of semantic activation, whereby processing is facilitated by the presence of semantic neighbors.     

Repetition Priming Follows Spontaneous but not Prompted Recognition of Familiar Faces

Reaction times to make a familiarity decision to the faces of famous people were measured after recognition of the faces in a pre-training phase had occurred spontaneously or following prompting with a name or other cue. At test, reaction times to familiar faces that had been recognized spontaneously in the pre-training phase were significantly facilitated relative to an unprimed comparison condition. Reaction times to familiar faces recognized only after prompting in the pre-training phase were not significantly facilitated. This was demonstrated both when a name prompt was used (Experiments 1 and 3) and when subjects were cued with brief semantic information (Experiment 2).

Repetition priming was not found to depend on prior spontaneous recognition per se. In Experiment 3, spontaneously recognizing a familiar face did not prime subsequent familiarity judgements when the same face had only been identified following prompting on a prior encounter. In Experiment 4, recognition memory for faces recognized after cueing was found to be over 90% accurate. This indicates that prompted recognition does not yield repetition priming, even though subjects can remember the faces. A fusion of “face recognition unit” and “episodic record” accounts of the repetition priming effect may be more useful than either theory alone in explaining these results.     

Bias in Conditional Inference: Implications for Mental Models and Mental Logic

Three experiments are reported in which subjects are given the opportunity to make any of the four inferences associated with conditional statements: modus ponens (MP), denial of the antecedent (DA), affirmation of the consequent (AC), and modus tollens (MT). The primary purpose of the research was to establish the generality and robustness of polarity biases that may be occasioned by systematic rotation of negative components in the conditional rules. In Experiments 1 & 2, three forms of conditionals were used: “if (not) p then (not) q”, “(not) p only if (not) q” and “(not) q if (not) p”. Experiment 1 used a conclusion evaluation task, whereas Experiment 2 used a conclusion production task. In Experiment 3, thematic conditionals were presented with and without a preceding scenario.

The biases investigated were (a) affirmative premise bias—the tendency to draw more inferences from affirmative premises and (b) negative conclusion bias—the tendency to draw more inferences with negative conclusions. The suggestive evidence for affirmative premise bias in the literature was not supported: very little evidence was found for it in the current experiments. Robust findings of negative conclusion bias were, however, found across the three experiments, although the bias was mostly restricted to DA and MT inferences. This suggests that the bias is best regarded as a difficulty with double negation.

The results are discussed with respect to both the mental logic and mental model accounts of propositional reasoning. Neither theory as currently formulated can explain all of our findings, although a plausible revision of each is considered.     

Comparative analysis of proprioception in left and right arms

Using the “kinaesthetic memory for the target” technique, differences in the accuracy of pointing to a target with the right and left arms are analysed. The effect of rotation of the head to left and right upon this process is also studied.

With the head normally orientated, it was found that pointing with the right arm is significantly better than with the left. Accuracy of pointing is greater with the target directly in front of the body than when it lies to either left or right side.

When the head is rotated, the direction of the pointing error is inversely related to the direction of rotation.

The study suggests that the precision of control over arm (in the absence of vision) is related to the varying ability of individual subjects to correlate limb movements with the prevailing orientation of the body, especially of the head and neck. This is additional to the influences of genetically-determined handedness and of the sensory input from the moving limb.