Gödel’s Natural Deduction

This is a companion to a paper by the authors entitled “Gödel on deduction”, which examined the links between some philosophical views ascribed to Gödel and general proof theory. When writing that other paper, the authors were not acquainted with a system of natural deduction that Gödel presented with the help of Gentzen’s sequents, which amounts to Ja?kowski’s natural deduction system of 1934, and which may be found in Gödel’s unpublished notes for the elementary logic course he gave in 1939 at the University of Notre Dame. Here one finds a presentation of this system of Gödel accompanied by a brief reexamination in the light of the notes of some points concerning his interest in sequents made in the preceding paper. This is preceded by a brief summary of Gödel’s Notre Dame course, and is followed by comments concerning Gödel’s natural deduction system.     

Social categorization as a function of priming

The present study investigates the effect of priming on the use of social categorizations. Using sex and race as stimulus categorizations, previous studies failed to confirm the hypothesis that priming one of the two available categorizations would enhance the use of the primed categorization relation to the not-primed categorization. As suggested by Stangor, Lynch, Duan and Glass (1992). a momentary increase in accessibility may be insufficient to further enhance the use of highly accessible categorizations like race and sex, but it may be expected that priming will increase the use of categorizations which are less habitually used in daily life. The results of the present experiment support the hypothesis that, when the stimulus categorizations are weakly accessible (university major, university town), the relative use of the previously primed categorizations does indeed increase, compared to the alternative, not-primed, categorization.     

Holistic face processing can be independent of gaze behaviour: Evidence from the composite face illusion

People tend to perceive identical top halves (i.e. above the nose) of two face stimuli as being different when they are aligned with distinct bottom halves. This composite face illusion is generally considered as the most compelling evidence that facial features are integrated into a holistic representation. Here, we recorded eye‐movements during the composite face illusion in a delayed matching task of top halves of faces. Behavioural results showed a strong composite face effect, participants making more mistakes and taking longer time to match two identical top halves of faces when they were aligned (vs. misaligned) with different bottom halves. Importantly, fixation sites and eye‐movements were virtually identical when the top and bottom parts were aligned (composite illusion) or misaligned (no illusion), indicating that holistic face processing can be independent of gaze behaviour. These findings reinforce the view that holistic representations of individual faces can be extracted early on from information at a relatively coarse scale, independently of overt attention.     

Forewarned is forearmed: Conserving self-control strength to resist social influence

Recent research has shown that resisting persuasion involves active self-regulation. Resisting an influence attempt consumes self-regulatory resources, and in a state of self-regulatory resource depletion, people become more susceptible to (unwanted) influence attempts. However, the present studies show that a forewarning of an impending influence attempt prompts depleted individuals to conserve what is left of their regulatory resources and thus promotes self-regulatory efficiency. As a result, when these individuals are subsequently confronted with a persuasive request, they comply less (Experiments 1 and 3), and generate more counterarguments (Experiment 2) than their depleted counterparts who were not forewarned and thus did not conserve their resources, and they are as able as non-depleted participants to resist persuasion.     

Action planning in young children's tool use

Tool use consists of at least two coupled phases of activities, involving multi-step problem solving. It therefore provides an interesting window on the development of planning in goal-directed behavior. This study investigated 2-year-olds' and 3-year-olds' hand use in picking up and subsequently using a tool for displacing a target-object towards a specified goal location. The children had to use a stick (Experiment 1; N = 41 in total) or a cane (hooked stick) that was lying in varying starting orientations (Experiment 2; N = 32 in total). Age differences were found in the way goal-related information in combination with tool-related information influenced the choice of which hand to use in different phases of the task. A view on action planning is developed as a dynamic action-selection process for which actions to take. This process integrates factors that are internal to the child's action system (e.g. motor preferences and dexterity) with external (i.e. sensory) sources of information.     

Remembering can cause inhibition: retrieval-induced inhibition as cue independent process

Previous experiments have mostly relied on recall as a dependent measure to assess whether retrieval of information from memory causes inhibition of related information. This study aimed to measure this inhibition in a more direct way. In Experiment 1, it was shown that repeated retrieval of exemplars from a category resulted in longer recognition latencies to nonretrieved exemplars from that same category, compared with recognition latencies to control exemplars. Experiment 2 obtained the same pattern of results using a lexical decision task. This was the 1st time that retrieval-induced forgetting was demonstrated on an implicit test of memory. To exclude noninhibitory explanations of the data, the exemplars were presented in both experiments without their categories as cues.     

Predicting Behavior From Actions in the Past: Repeated Decision Making or a Matter of Habit?

This paper summarizes research on determinants of repeated behaviors, and the decision processes underlying them. The present research focuses on travel mode choices as an example of such behaviors. It is proposed that when behavior is performed repeatedly and becomes habitual, it is guided by automated cognitive processes, rather than being preceded by elaborate decision processes (i.e., a decision based on attitudes and intentions). First, current attitude-behavior models are discussed, and the role of habit in these models is examined. Second, research is presented on the decision processes preceding travel mode choices. Based on the present theoretical and empirical overview, it is concluded that frequently performed behavior is often a matter of habit, thereby establishing a boundary condition for the applicability of attitude-behavior models. However, more systematic research is required to disentangle the role of habit in attitude-behavior models and to learn more about the cognitive processes underlying habitual behavior.     

Does quantity generate quality? Testing the fundamental principle of brainstorming

The purpose of this work is to test the chief principle of brainstorming, formulated as "quantity generates quality." The study is included within a broad program whose goal is to detect the strong and weak points of creative techniques. In a sample of 69 groups, containing between 3 and 8 members, the concurrence of two commonly accepted criteria was established as a quality rule: originality and utility or value. The results fully support the quantity-quality relation (r = .893): the more ideas produced to solve a problem, the better quality of the ideas. The importance of this finding, which supports Osborn's theory, is discussed, and the use of brainstorming is recommended to solve the many open problems faced by our society.