John Clibbens

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.

Explicit and implicit processes in multicue judgment.

In two experiments, a multicue probability learning task was used to train participants in relating judgments to a criterion, on the basis of several cues that could or could not be relevant. The outcome feedback had 25% added noise to simulate real-world experience-based learning. Judgmental strategies acquired were measured by individual multiple linear regression analyses of a test phase (with no feedback) and were compared with self-ratings of cue relevance. In a third experiment, participants were instructed explicitly on cue relevance, with no training phase. The pattern of results suggested that both implicit and explicit cognitive processes influenced judgments and that they may have been sensitive to different task manipulations in the learning phase. On more complex tasks, despite weak explicit learning, explicit processes continued to influence judgments, producing a decrement in performance. These findings explain why studies of expert judgment often show only moderate levels of self-insight, since people have only partial access to the processes determining their judgments.

Visual memory for shapes in deaf signers and nonsigners and in hearing signers and nonsigners: atypical lateralization and enhancement.

Deaf and hearing individuals who either used sign language (signers) or not (nonsigners) were tested on visual memory for objects and shapes that were difficult to describe verbally with a same/different matching paradigm. The use of 4 groups was designed to permit a separation of effects related to sign language use (signers vs. nonsigners) and effects related to auditory deprivation (deaf vs. hearing). Forty deaf native signers and nonsigners and 51 hearing signers and nonsigners participated in the study. Signing individuals (both deaf and hearing) were more accurate than nonsigning individuals (deaf and hearing) at memorizing shapes. For the shape memory task but not the object task, deaf signers and nonsigners displayed right hemisphere (RH) advantage over the left hemisphere (LH). Conversely, both hearing groups displayed a memory advantage for shapes in the LH over the RH. Results indicate that enhanced memory performance for shapes in signers (deaf and hearing) stems from the visual skills acquired through sign language use and that deafness, irrespective of language background, leads to the use of a visually based strategy for memory of difficult-to-describe items.

Strategies for achieving joint attention when signing to children with Down's syndrome

Research indicates that joint attention is an important factor in determining the rate and nature of early vocabulary development in typically developing children. Studies conducted with deaf children acquiring sign language indicate that caregivers adopt special strategies for achieving joint attention with this group: these strategies make allowance for the visual medium in which the language is transmitted. Joint attention is also important for the development of communication in children with Downs syndrome, who also often have restricted attentional capacity. Moreover, there is good evidence that the use of signed input in addition to speech can have significant benefits for these children. This paper reports on a study designed to explore the utility of strategies observed in deaf parents for the achievement of joint attention when signing with children with Downs syndrome. Data are presented from recordings of four children with Downs syndrome and their mothers. The results showed that the mothers were successful in enabling the child to perceive both signed input and contextual referents much of the time, but that the range of strategies used was very limited compared to deaf parents of deaf children. Adopting a wider range of strategies would allow a considerable increase in signed input. Implications for intervention programmes are discussed.

Background beliefs and evidence interpretation

In this paper we argue that it is often adaptive to use ones background beliefs when interpreting information that, from a normative point of view, is incomplete. In both of the experiments reported here participants were presented with an item possessing two features and were asked to judge, in the light of some evidence concerning the features, to which of two categories it was more likely that the item belonged. It was found that when participants received evidence relevant to just one of these hypothesised categories (i.e. evidence that did not form a Bayesian likelihood ratio) they used their background beliefs to interpret this information. In Experiment 2, on the other hand, participants behaved in a broadly Bayesian manner when the evidence they received constituted a completed likelihood ratio. We discuss the circumstances under which participants, when making their judgements, consider the alternative hypothesis. We conclude with a discussion of the implications of our results for an understanding of hypothesis testing, belief revision, and categorisation.

Atypical Lateralization of Memory for Location: Effects of Deafness and Sign Language Use.

This paper examines the impact of auditory deprivation and sign language use on the enhancement of location memory and hemispheric specialization using two matching tasks. Forty-one deaf signers and non-signers and 51 hearing signers and non-signers were tested on location memory for shapes and objects (Study 1) and on categorical versus coordinate spatial relations (Study 2). Results of the two experiments converge to suggest that deafness alone supports the atypical left hemispheric preference in judging the location of a circle or a picture on a blank background and that deafness and sign language experience determine the superior ability of memory for location. The importance of including a sample of deaf non-signers was identified.

Perspective Shifts on the Selection Task: Reasoning or Relevance?

The single most investigated problem in the psychology of reasoning is the Wason selection task (see Evans, Newstead, & Byrne, 1993, Chapter 4 for a detailed review). Nevertheless, there is room for considerable doubt as to whether subjects choices on this task actually reflect a process of reasoning at all, as we shall argue here (see also Evans, in press). Selection task studies can broadly be divided into those using abstract or arbitrary problem content and those using thematic content. At one time it appeared that subjects were very poor at solving the abstract task but quite good on the thematic task, but we now know this to be a double simplification. First, there are manipulations that cause subjects to choose largely correctly on the abstract task (see Platt & Griggs, 1993, 1995), and second, the pragmatic influences introduced by realistic content can sometimes trigger non-normative selection patterns. The Wason selection task is described by Holyoak and Cheng (this issue) and will not be repeated in detail here. Suffice it to say that subjects are asked to test a rule of the form if p then q by deciding whether or not to tum over each of four cards displaying the values p, not-p, q, and not-q. If the facing side of the card provides information about the antecedent of the rule, then the hidden side will provide information about the consequent, and vice versa. The logically correct choices are the cards p and not-q which could provide evidence that a card violates the rule. This choice is rarely observed on the abstract task where arbitrary relations such as If there is a vowel on one side of the card then there is a consonant on the other side of the card are used. It has been known for many years, however, that certain kinds of thematic phrasings of the rule, together with an appropriate context, will produce this logically Correct pattern. One of the most important new findings in this literature in recent years is that the pattern of selections observed can be radically altered by instructions that manipulate the perspective of the subject in terms of which character they identify with in a scenario. For example, given the statement:

Prior belief and polarity in multicue learning.

We report two experiments in which participants are trained using a multicue probability learning (MCPL) task, which attempts to simulate the acquisition of expert judgement by experience in the real world. Participants were asked to predict performance in certain occupations given a profile of personality test results with trial-by-trial outcome feedback. Only some cues were relevant, and the polarity of the cues (positive or negative predictors) was unspecified. In addition, 25% of random noise was added to the feedback to simulate real world uncertainty. The main factor of interest was that the role of prior belief (determined in a separate study of stereotypes) interfered with the learning process. Experiment 1 failed to find any influence of prior belief in the cues that were irrelevant to the criterion being trained. However, in Experiment 2 people learned to use the relevant cues better when their effect conformed with rather than conflicted with prior belief. Both experiments showed strong effects of cue polarity, with positive predictors much more easily learned. The results are discussed with reference to the cognitive processes involved in MCPL and closely related tasks.

Where's the orange ? Geometric and extra-geometric influences on English children's descriptions of spatial locations*

The effect of both geometric and extra-geometric factors on childrens production of in is reported (free-response paradigm). Eighty children across four age groups (means 4;1, 5;5, 6;1, and 7;1) were shown video scenes of puppets placing real objects in various positions with reference to a bowl and a plate. Located objects were placed at three heights on top of piles of other objects in the scene. The extrageometric factor of location control of the located object was manipulated by comparing static scenes to dynamic scenes in which the located object was depicted as either moving independently of, or together with, the reference object. Additionally, the located object was placed on other objects that were either the same or different (e.g. an apple on apples or on oranges). The results indicate that even the youngest children altered the way they talked according to not only geometric but also extra-geometric factors.

Visual speech aids: A British survey of use and evaluation by speech and language therapists

One hundred and eighty speech and language therapists throughout the UK completed a postal questionnaire which asked for ratings of visual speech aids (VSAs) on a number of dimensions together with information regarding frequency of use of such aids, comments on the range of applicability of each type of aid and other demographic data relating to the diversity of client groups covered in case loads. The results (using analysis of variance) revealed a main effect of VSA type. There was also a main effect of question type; all VSAs scored poorly on some dimensions as compared with others. Furthermore there was a significant interaction between type of VSA and dimension type. This suggests that VSAs not only tend to be built for particular client groups, but that the makers tend to focus on some specific design criteria to the detriment of others. These results are discussed with respect to the future design of VSAs, and with respect to their testing and future evaluation.