Hypothesis-testing strategies: Why two goals are better than one

An intriguing finding in the hypothesis-testing literature concerns a large increase in the proportion of subjects who discover a rule when they are asked to determine two rules rather than that rule alone. This finding is based on Wason's (1960) “2 4 6” task, in which subjects try to discover a rule (ascending numbers) by generating and testing number triples. They are initially given an example (“2, 4, 6”) of the rule that leads to overly specific hypotheses. With single-goal (SG) instructions, subjects try to discover the correct rule and are told whether each triple proposed fits the rule. With dual-goal (DG) instructions, correct and incorrect categories are labelled, respectively, as DAX and MED. Subjects try to discover both rules and are told whether each proposed triple is DAX or MED. Two explanations of why DG subjects do better at rule discovery than SG subjects are tested: the quantity of information and the testing of complementary rules using the prevalent positive-test strategy. Results support the latter explanation: DG subjects outperform SG subjects only if they know the rules are complementary, and that SG subjects' performance does not improve when required to test more triples before announcing their first rule. A third explanation, the positivity of the linguistic label of the feedback, is ruled out. Understanding the superiority of DG instructions might suggest a general method for enhancing rule discovery.     

Explaining avoidance: two factors are still better than one.

Two-factor theory remains a viable account of avoidance behavior. By emphasizing the interplay of respondent and operant contingencies, two-factor theory encourages the analysis of stimuli that mediate molar consequences and incorporates control by local events as well as events that are temporally remote, improbable, or cumulative.     

Enhancing lineup identification accuracy: two codes are better than one

Ways of improving identification accuracy were explored by comparing the conventional visual lineup with an auditory/visual lineup, one that paired color photographs with voice recordings. This bimodal lineup necessitated sequential presentation of lineup members; Experiment 1 showed that performance in sequential lineups was better than performance in traditional simultaneous lineups. In Experiments 2A and 2B unimodal and bimodal lineups were compared by using a multiple-lineup paradigm: Ss viewed 3 videotaped episodes depicting standard police procedures and were tested in 4 sequential lineups. Bimodal lineups were more diagnostic than either visual or auditory lineups alone. The bimodal lineup led to a 126% improvement in number of correct identifications over the conventional visual lineup, with no concomitant increase in number of false identifications. These results imply strongly that bimodal procedures should be adopted in real-world lineups. The nature of memorial processes underlying this bimodal advantage is discussed.     

When two limbs are weaker than one: Sensorimotor syncopation with alternating hands

This study addresses the demands of alternating bimanual syncopation, a coordination mode in which the two hands move in alternation while tapping in antiphase with a metronomic tone sequence. Musically trained participants were required to engage in alternating bimanual syncopation and five other coordination modes: unimanual syncopation where taps are made (with the left or right hand) after every tone; unimanual syncopation where taps are made after every other tone; bimanual synchronization with alternating hands; unimanual synchronized tapping with every tone; and unimanual tapping with every other tone. Variability in tap timing was greatest overall for alternating bimanual syncopation, indicating that it is the most difficult. This appears to be due to instability arising from the simultaneous presence of two levels of antiphase coordination (one between the pacing sequence and the hands, the other between the two hands) rather than factors relating to movement frequency or dexterity limits of the nonpreferred hand.     

Multisensory temporal order judgments: when two locations are better than one

In Experiment 1, participants were presented with pairs of stimuli (one visual and the other tactile) from the left and/or right of fixation at varying stimulus onset asynchronies and were required to make unspeeded temporal order judgments (TOJs) regarding which modality was presented first. When the participants adopted an uncrossed-hands posture, just noticeable differences (JNDs) were lower (i.e., multisensory TOJs were more precise) when stimuli were presented from different positions, rather than from the same position. This spatial redundancy benefit was reduced when the participants adopted a crossed-hands posture, suggesting a failure to remap visuotactile space appropriately. In Experiment 2, JNDs were also lower when pairs of auditory and visual stimuli were presented from different positions, rather than from the same position. Taken together, these results demonstrate that people can use redundant spatial cues to facilitate their performance on multisensory TOJ tasks and suggest that previous studies may have systematically overestimated the precision with which people can make such judgments. These results highlight the intimate link between spatial and temporal factors in determining our perception of the multimodal objects and events in the world around us.     

Sociosexual attitudes and behaviors: Why two factors are better than one

Researchers have recently questioned the unidimensionality of the sociosexual orientation inventory [SOI; Simpson, J. A., & Gangestad, S. W. (1991). Individual differences in sociosexuality: evidence for convergent and discriminant validity. Journal of Personality and Social Psychology, 60, 870–883], which measures willingness to engage in uncommitted sexual relationships. Previous research, however, has not empirically examined this issue. Thus, 2787 undergraduates completed measures of the SOI, narcissism, and hostility. Confirmatory factor analyses revealed that a dual-factor model of the SOI, which accounted for both behavioral (Items 1–3) and attitudinal (Items 2, 4–7) components, fit the data significantly better than a single-factor model. Although gender did not moderate the factor loadings, the sociosexual attitude-behavior correlation was stronger for women than for men. Sociosexual attitudes and behaviors were differentially related to narcissism and hostility. Researchers should consider scoring the SOI as separate attitudinal and behavioral components.     

When two heads are not better than one: Partner neglect in paired memory tasks

People can monitor the accuracy of their own memories and regulate their responses accordingly. But can they monitor and make use of another person’s memory? We document a new phenomenon whereby participants neglect a partner’s expertise when deciding whether to defer to that partner’s memory or to rely on their own. In two experiments, participants studied images for more time than, less time than, or the same amount of time as a partner, and on subsequent recognition tests they were directed to maximize team performance by either answering themselves or letting their partner respond. In both experiments, individuals failed to use the knowledge that the partner would probably have a better memory for certain items. Only when explicitly instructed to estimate their accuracy relative to their partner’s did participants take advantage of the partner’s greater expertise. Psychonomic Society, Inc.     

Two hands are better than one: a new assessment method and a new interpretation of the non-visual illusion of self-touch

A simple experimental paradigm creates the powerful illusion that one is touching one’s own hand even when the two hands are separated by 15 cm. The participant uses her right hand to administer stimulation to a prosthetic hand while the Examiner provides identical stimulation to the participant’s receptive left hand. Change in felt position of the receptive hand toward the prosthetic hand has previously led to the interpretation that the participant experiences self-touch at the location of the prosthetic hand, and experiences a sense of ownership of the prosthetic hand. Our results argue against this interpretation. We assessed change in felt position of the participant’s receptive hand but we also assessed change in felt position of the participant’s administering hand. Change in felt position of the administering hand was significantly greater than change in felt position of the receptive hand. Implications for theories of ownership are discussed.     

Two are better than one: comparison influences infants' visual recognition memory

Despite a large literature on infants’ memory for visually presented stimuli, the processes underlying visual memory are not well understood. Two studies with 4-month-olds (N = 60) examined the effects of providing opportunities for comparison of items on infants’ memory for those items. Experiment 1 revealed that 4-month-olds failed to show evidence of memory for an item presented during familiarization in a standard task (i.e., when only one item was presented during familiarization). In Experiment 2, infants showed robust memory for one of two different items presented during familiarization. Thus, infants’ memory for the distinctive features of individual items was enhanced when they could compare items.     

Quantity versus uncertainty: When winning one prize is better than winning two

We predicted that a state of uncertainty would prolong a positive mood, but that people would not anticipate this when making affective forecasts. In Study 1, participants learned that they had won one prize (certain condition), two prizes (two-gift condition), or one of two prizes (uncertain condition). People in the uncertain condition were in a positive mood longer than people in the other two conditions. In Study 2, forecaster participants underestimated the benefits of uncertainty and overestimated the benefits of quantity (getting two gifts instead of one). Under some circumstances, and contrary to people’s predictions, uncertainty can prolong positive mood, and winning one prize under a state of uncertainty can bring more short-term pleasure than winning two prizes.     

Converging on a new role for analogy in problem solving and retrieval: when two problems are better than one

People often fail to retrieve examples analogous to a current problem or situation. There is good evidence that comparing structurally matching cases facilitates subsequent analogical access. However, current approaches offer little at the time of memory search to promote retrieval of a routinely encoded analogous source. We adapted Gick and Holyoak's (1980, 1983) classic paradigm to investigate whether comparing two unsolved problems at test promotes retrieval of a single previously studied analogue. In Experiment 1, comparison of test problems facilitated analogical problem solving. Experiment 2 showed that comparison is the critical factor since solving two test problems separately proved ineffective. In Experiment 3, comparing two problems led to greater success for participants who read a prior analogous story than those who did not, demonstrating specifically that comparison facilitates retrieval. The three studies show that analogical access is powerfully determined by problem encoding. Implications for psychological theory and real-world applications are discussed.     

Four heads are better than one: combining face composites yields improvements in face likeness

Four participants constructed face composites, of familiar and unfamiliar targets, using Pro-Fit, with reference images present or from memory. The "mean" of all 4 composites, created by morphing (4-morph) was rated as a better likeness than individual composites on average and was as good as the best individual likeness. When participants attempted to identify targets from line-ups, 4-morphs again performed as well as the best individual composite. In a second experiment, participants familiar with target women attempted to identify composites, and the trend showed better recognition from multiple composites, whether combined or shown together. In a line-up task with unfamiliar participants, 4-morphs produced most correct choices and fewest false positives from target-absent or target-present arrays. These results have practical implications for the way evidence from different witnesses is used in police investigations.     

Increasing compliance with a request: two touches are more effective than one

Touch procedures have been shown to increase the likelihood of compliance with requests. But the effect of subsequent touches following a classical touch procedure has not been investigated. It was predicted that two touches would lead to more compliance than one touch. 180 male and 180 female bystanders were asked to fill in a short or long questionnaire by a female confederate. They were touched by the confederate either once, twice, or not at all. Results showed that there was more compliance in the two-touch than in the one-touch condition, and when the participants were touched by the confederate. These findings support the hypothesis. Moreover, whereas participants were less likely to fill in the long questionnaire in the no-touch condition, touch procedures led to more compliance whatever the questionnaire length. Also, touch was more effective when a female confederate made the request to a male participant.     

Two spatial memories are not better than one: evidence of exclusivity in memory for object location

This paper studies the dynamics of attempting to access two spatial memories simultaneously and its implications for the accuracy of recall. Experiment 1 demonstrates in a range of conditions that two cues pointing to different experiences of the same object location produce little or no higher recall than that observed with a single cue. Experiment 2 confirms this finding in a within-subject design where both cues have previously elicited recall. Experiment 3 shows that these findings are only consistent with a model in which two representations of the same object location are mutually exclusive at both encoding and retrieval, and inconsistent with models that assume information from both representations is available. We propose that these representations quantify directionally specific judgments of location relative to specific anchor points in the stimulus; a format that precludes the parallel processing of like representations. Finally, we consider the apparent paradox of how such representations might contribute to the acquisition of spatial knowledge from multiple experiences of the same stimuli.     

Vertical-horizontal illusion: One eye is better than two

The vertical-horizontal illusion is the tendency for observers to overestimate the length of a vertical line relative to a horizontal line that has the same length. One explanation of this illusion is that the visual field is elongated in the horizontal direction, and that the vertical-horizontal illusion is a kind of framing effect (Künnapas, 1957a, 1957b, 1957c). Since the monocular visual field is less asymmetric than the combined visual field, this theory predicts that the illusion should be reduced with monocular presentation. This prediction was tested in five experiments, in which the vertical-horizontal illusion was examined in a variety of situations—including observers seated upright versus reclined 90°, monocular presentation with the dominant versus the nondominant eye, viewing in the dark versus in the light, and viewing with asymmetrical frames of reference. The illusion was reliably reduced with monocular presentation under conditions that affected the asymmetry of the phenomenal visual field.     

Two is better than one, but mine is better than ours: Preschoolers’ executive function during co-play

The current study investigated how playing with another individual may influence 3- and 4-year-olds’ executive function in the Less-Is-More (LIM) task, where children point to the tray with the smaller amount of treats so as to obtain the larger amount of treats in the other tray. In Experiment 1, 35 Singaporean children were tested with a self version and a co-player-split version of the LIM task. Results showed that children appeared to be less impulsive when playing with a co-player than when playing individually. Experiment 2 further investigated how the intention of the co-player, collective profit oriented versus individual profit oriented, may influence children’s executive function. In total, 96 children were tested with a self version, a co-player-share version, and a co-player-opponent version. Results showed that the co-playing facilitation effect appeared in only the co-player-opponent version. Together, the results of the current study showed that when preschoolers play with an individual who shares a common goal with them, they may become more efficient in executive control.     

When two actions are easier than one: How inhibitory control demands affect response processing

Numerous studies showed that the simultaneous execution of multiple actions is associated with performance costs. Here, we demonstrate that when highly automatic responses are involved, performance in single-response conditions can actually be worse than in dual-response conditions. Participants responded to peripheral visual stimuli with an eye movement (saccade), a manual key press, or both. To manipulate saccade automaticity, a central fixation cross either remained present throughout the trial (overlap condition, lower automaticity) or disappeared 200 ms before visual target onset (gap condition, greater automaticity). Crucially, single-response conditions yielded more performance errors than dual-response conditions (i.e., dual-response benefit), especially in gap trials. This was due to difficulties associated with inhibiting saccades when only manual responses were required, suggesting that response inhibition (remaining fixated) can be even more resource-demanding than overt response execution (saccade to peripheral target).     

Recognising faces seen alone or with others: when two heads are worse than one

There is a large body of work investigating face identification, but most of this addresses recognition of a single person. Here, we examine how recognition is affected by the presence of a second face. In Experiments 1 and 2, we demonstrate that memory for an unfamiliar face is severely reduced if it is seen alongside a second person. Sequential presentation of two target faces further reduces accuracy. In Experiments 3 and 4, we demonstrate the same disadvantage for two‐face targets in a matching task, where subjects have no time limits or memory requirement. In matching, the damaging effect of a second face is greatest when the targets are placed close together. Furthermore, there is a general advantage for faces presented to the left. We suggest that it may not be possible to extrapolate results from single‐face studies to experiments (or realistic situations) involving more than one person. Copyright © 2006 John Wiley & Sons, Ltd.