The confluence model: birth order as a within-family or between-family dynamic?

The confluence model explains birth-order differences in intellectual performance by quantifying the changing dynamics within the family. Wichman, Rodgers, and MacCallum (2006) claimed that these differences are a between-family phenomenon--and hence are not directly related to birth order itself. The study design and analyses presented by Wichman et al. nevertheless suffer from crucial shortcomings, including their use of unfocused tests, which cause statistically significant trends to be overlooked. In addition, Wichman et al. treated birth-order effects as a linear phenomenon thereby ignoring the confluence model's prediction that these two samples may manifest opposing results based on age. This article cites between- and within-family data that demonstrate systematic birth-order effects as predicted by the confluence model. The corpus of evidence invoked here offers strong support for the assumption of the confluence model that birth-order differences in intellectual performance are primarily a within-family phenomenon.

Beliefs about birth rank and their reflection in reality.

Beliefs about birth rank reflect what the society regards as social reality, and they may also influence that reality. Three studies found that people believe those with different birth ranks differ in their personalities, that higher birth ranks are likely to attain higher occupational prestige, and that the personality characteristics attributed to the various birth ranks favor the actual attainment of higher occupational prestige. In one example of such beliefs, firstborns were rated as most intelligent but least creative whereas the opposite was true of last-borns. The 4th study found that those with higher birth ranks in fact attain more prestigious occupations and actually do complete more years of schooling.

The family dynamics of intellectual development.

Birth order effects on intellectual performance show both positive and negative results. The confluence model reconciles these conflicting data by proving that these effects interact with the age of participants at testing, such that young children should show negative or no effects, whereas older individuals (past age 11 +/- 2 years) should show positive effects. Birth order studies strongly support this prediction. Some writers have claimed the apparent relation between birth order and intelligence is an artifact created by applying a cross-sectional analysis to data that should have been analyzed by comparing siblings within families. However, if siblings within the same family are compared all at the same time, their ages are necessarily different. As a result, birth order effects are confounded with age effects. Moreover, within-family data conceal patterns of aggregate effects that cross-sectional data reveal.

The mere exposure effect in patients with schizophrenia.

The mere exposure effect refers to the development of an emotional preference for previously unfamiliar material because of frequent exposure to that material. This study compared schizophrenia subjects (n = 20) to normal controls (n = 21) to determine whether implicit memory, as demonstrated by the mere exposure effect, was intact. Patients with schizophrenia demonstrated a normal preference for both verbal and visual materials seen earlier relative to novel materials, despite impaired performance on a recognition task for explicit memory using similar materials. Previous studies of schizophrenia subjects have shown a dissociation between implicit and explicit memory on verbal tasks. We found a similar dissociation demonstrated by normal functioning on an implicit memory task and impaired functioning on an explicit memory task. Potential implications of these findings are discussed with regard to treatment and rehabilitation.

Subliminal mere exposure: specific, general, and diffuse effects.

The present research examined the possibility that repeated exposure may simultaneously produce specific and diffuse effects. In Study 1, participants were presented with 5-ms exposures of 25 stimuli each shown once (single-exposure condition) or with five repetitions of 5 stimuli (repeated-exposure condition). Participants in the repeated-exposure condition subsequently rated their own mood more positively than those in the single-exposure condition. Study 2 examined whether affect generated by subliminal repeated exposures transfers to unrelated stimuli. After a subliminal exposure phase, affective reactions to previously exposed stimuli, to new but similar stimuli, and to stimuli from a different category were obtained. Previously exposed stimuli were rated most positively and novel different stimuli least positively. All stimuli were rated more positively in the repeated-exposure condition than in the single-exposure condition. These findings suggest that affect generated by subliminal repeated exposure is sufficiently diffuse to influence ratings of unrelated stimuli and mood.

Additivity of nonconscious affect: combined effects of priming and exposure.

Affect deriving from 2 independent sources--repeated exposure and affective priming--was induced, and the combined effects were examined. In each of 4 studies, participants were first shown 72 Chinese ideographs in which the frequency of exposure was varied (0, 1, or 3). In the second phase participants rated ideographs that were primed either positively, negatively, or not at all. The 4 studies were identical except that the exposure duration--suboptimal (4 ms) or optimal (1 s)--of both the initial exposure phase and the subsequent priming phase was orthogonally varied. Additivity of affect was obtained only when affective priming was suboptimal, suggesting that nonconscious affect is diffuse. Affect whose source was apparent was more constrained. Interestingly, increases in liking generated through repeated exposures did not differ as a function of exposure duration.

Affect, cognition, and awareness: affective priming with optimal and suboptimal stimulus exposures.

The affective primacy hypothesis (R. B. Zajonc, 1980) asserts that positive and negative affective reactions can be evoked with minimal stimulus input and virtually no cognitive processing. The present work tested this hypothesis by comparing the effects of affective and cognitive priming under extremely brief (suboptimal) and longer (optimal) exposure durations. At suboptimal exposures only affective primes produced significant shifts in Ss' judgments of novel stimuli. These results suggest that when affect is elicited outside of conscious awareness, it is diffuse and nonspecific, and its origin and address are not accessible. Having minimal cognitive participation, such gross and nonspecific affective reactions can therefore be diffused or displaced onto unrelated stimuli. At optimal exposures this pattern of results was reversed such that only cognitive primes produced significant shifts in judgments. Together, these results support the affective primacy hypothesis.

Emotion and facial efference: a theory reclaimed.

A theory of emotional expression, ignored since 1906, holds that facial muscles act as ligatures on facial blood vessels and thereby regulate cerebral blood flow, which, in turn, influences subjective feeling. The theory, developed by Israel Waynbaum, a French physician, hypothesizes the subjective experience of emotions as following facial expression rather than preceding it. It answers Darwin's question of why different muscles contract or relax in different emotions better than Darwin's own theory. When restated in terms of contemporary neurophysiological knowledge, it explains and organizes several ill-understood emotional processes and phenomena.

Affective discrimination of stimuli that cannot be recognized.

Animal and human subjects readily develop strong preferences for objects that have become familiar through repeated exposures. Experimental evidence is presented that these preferences can develop even when the exposures are so degraded that recognition is precluded.

The birth order puzzle.

Studies relating intellectual performance to birth order report conflicting results, some finding intellectual scores to increase, others to decrease with birth order. In contrast, the relationship between intellectual performance and family size is stable and consistently replicable. Why do these two highly related variables generate such divergent results? This birth order puzzle is resolved by means of the confluence model that quantifies the influences upon intellectual growth arising within the family context. At the time of a new birth, two opposing influences act upon intellectual growth of the elder sibling: (a) his or her intellectual environment is "diluted" and (b) he or she loses the "last-born's handicap" and begins serving as an intellectual resource to the younger sibling. Since these opposite effects are not equal in magnitude, the differences in intellectual performance among birth ranks are shown to be age dependent. While elder children may surpass their younger siblings in intellectual performance at some ages, they may be overtaken by them at others. Thus when age is taken into consideration, the birth order literature loses its chaotic character and an orderly pattern of results emerges.

Is stimulus recognition a necessary condition for the occurrence of exposure effects?

Many theories of exposure effects involve the operation of psychological processes that depend on some form of stimulus recognition. Two experiments investigated the role of stimulus recognition in the mere exposure phenomenon. Female subjects viewed novel stimuli at various exposure frequencies, then measures of stimulul recognition and effect were obtained. In each experiment, a significant and positive relationship was found between stimulus exposure and affect, even when the effects of stimulus recognition were held constant. Thus, stimulus recognition was not a necessary condition for the occurrence of the observed exposure effects. The results suggest that the relationship between stimulus exposure and affect does not depend on the operation of higher order cognitive processes, at least to the extent that such processes are themselves dependent upon stimulus recognition.

Affiliation and social discrimination produced by brief exposure in day-old domestic chicks.

Discrimination between individual strangers and companions was examined in day-old domestic chicks. In one experiment, pecking rates at companions and strangers were observed in pairwise bouts after 16 hr of cohabitation. The discriminability of strangers and companions was varied by means of pre-hatch colouring. Reliable discriminations between individual strangers and companions emerged as early as the first minute of the encounter. Discriminative cues provided by artificial colouring were found not to be necessary in establishing social discrimination. In a second experiment, undyed chicks were housed in pairs for 1, 4 or 16 hr. Half of the pairs lived in cages that separated companions by a wire screen, and half were housed in undivided cages. Observations of pecking in four-way bouts confirmed previous findings and demonstrated that the opportunity to peck during exposure may be a necessary condition in producing social discrimination. Antecedent conditions that lead to the development of affiliative bonds simultaneously appear to establish social discrimination.