Birth Order Influences the Formation of Long-Term Relationships

134 years since Francis Galton opened the birth order effects debate by observing that first-born sons and only sons were over-represented among English scientists, controversy has shrouded the issue such that we haven't quite gotten past whether birth order effects exist or not, let alone properly consider what they are or how they work.

Some scholars assert that the lack of conclusive evidence is due to methodological biases that may allow the researcher to find the result that he or she is looking for. So, in that sense, a researcher who seeks to confirm that the birth order effect exists may find it just as well as a researcher who seeks to disconfirm it might.

In Birth Order Effects in the Formation of Long-Term Relationships, Hartshorne, Salem-Hartshorne and Hartshorne seek to probe the birth effect in a manner that is as methodologically neutral as possible by simply determining if there are any correlations between the sharing of birth order and the likelihood of long-term relationship formation. Their results provide new research material that weighs in favour of the presence of birth order effects, though what drives this effect is still speculative.

By drawing on a sample of 900 US undergraduate students, the researchers found that people are more likely to form and be in long-term relationships, both friendly and romantic, if they share the same birth order than would be expected by chance. For instance, if I were a first-born child, the likelihood of me being close friends with another first-born child is higher than the likelihood of me being close friends with another second- or third-born child. This tendency was also found for romantic partners.

A second and similar web-based study was conducted which gathered responses from American participants (1,911) as well as participants from other parts of the world (713). Similar results were garnered. There was no significant difference detected between American and non-American respondents, suggesting that birth order effects on long-term relationships are not culturally variant.

The researchers also controlled for socioeconomic status and size of family, which is a progressive extension from other earlier studies. This eliminates the confounds of number of siblings one has and the socioeconomic class one belongs to, which can potentially influence one's development because it is a commonly known social phenomenon that wealthier and upper class families tend to have less offspring.

The authors surmise that birth order underlies personality traits and having the same birth order results in greater compatibility between personality types, leading to the formation of closer bonds in both friendships and romantic relationships.

Joshua K. Hartshorne, Nancy Salem-Hartshorne, and Timothy S. Hartshorne (2009). Birth Order Effects in the Formation of Long-Term Relationship Journal of Individual Psychology, 65 (2)

Effects of sleep on Remembering to Remember

Prospective memory is a class of memory that is unique in that it involves the future rather than the present or the past. Various examples of prospective memory include remembering to buy a pet monkey, or remembering to break up with your girlfriend or remembering to do that blasted thesis that you have been putting off for the umpteenth time. Hence, some researchers have called it the act of "remembering to remember" (Winograd, 1988). Although prospective memory is quite important for daily functioning and goal fulfilment, research on it has been quite sparse in comparison to other forms of memory. One big question remains: how do we remember to remember? Do we devote some resources to maintain this intention? Or is it maintained without anything being devoted to it?

You know you want it.

One theory of prospective memory suggests that prospective memory can be both effortful and automatic. One way in which prospective memory can be automatic is when cues in our environment alert us to something we have to do. Kvavilashvili and Fisher (2007) has found that individuals often encounter cues related to a goal (eg, seeing a monkey in the magazine, receiving a text message from the girlfriend) and these cues spontaneously remind participants of their goal. Another way in which prospective memory is maintained is through conscious retrieval. Other researchers have also found that prospective memory surprisingly is better after 15 minutes than 3 minutes, one interpretation being that participants consciously retrieve and rehearse the goal prior to and up to the point when they are going to execute it (Hicks, Marsh & Cook, 2005).

One question that arises from these findings is that, what happens when we sleep on something? During sleep it appears that both automatic and effortful mechanisms are absent; we don't consciously retrieve and rehearse goals, and we aren't exposed to cues from the external environment. In such a case we might expect that prospective memory would weaken. However, given that a huge amount of literature has also shown that sleep improves memory, we might expect that sleep would improve prospective memory. These contradictory hypotheses form the basis for Scullin and McDaniel's study, "Remembering to execute a Goal: Sleep on it!" (2010)

The researchers had participants do a series of tasks (too lengthy to cover), while remembering to do a particular action at a particular time ("press the Q key when you see the word table or horse"). In one set of participants, this target came after a short delay (20 minutes) while in the long delay condition, participants were told to come back after 12 hours for another series of experiments and the target came there. The other crucial manipulation was time of day, the experiment for one set of participants was started in the morning, and the other set at night. The study was between groups, so participants were spread out across 4 conditions.

1. Short Morning Delay

2. Short Evening Delay

3. Wake Delay (from morning to night, during which time the participant was awake)

4. Sleep Delay (from night to morning, during which time the participant was sleeping)

What the researchers found was that sleeping improved the ability to remember to do something, as compared to being awake. In some of the tests, the performance was almost as good as if one was tested after 20 minutes. One important possible confound in this experiment was that the sleep and awake conditions also differed not just in amount of sleep but also when the experiment was conducted. The authors eliminated this confound by comparing performance for prospective memory during the day and night after a short delay and found that time of day had little effect.

So the results are inconsistent with the idea that sleep might undermine prospective memory by preventing conscious retrieval or exposure to environmental stimuli. It seems like prospective memory might not rely heavily on these 2 processes, as suggested by some proponents of the theory above. The implication being that if you need to remember to do something, you might as well sleep on it.

But how does sleep improve prospective memory? The authors suggest that sleep increases associative binding and that it amplifies weak goals or links. In this case, it seems like prospective memory might not be very much different from other types of memory. However the authors find that sleep improves prospective memory for only certain types of tasks, thus raising new avenues for research into different kinds of prospective memory and how they are affected by different variables.

One problem which I found in this paper was that the participants were engaging in quite an unnatural prospective memory task, in which case environmental cues present during the awake phase would not help the participant in remembering to do the task. On the other hand, in the real world, such environmental cues would be present and abundant (like seeing your thesis supervisor). So in that sense, the authors can't make the claim that sleeping improves prospective memory more than staying awake and being exposed to constant pictures of monkeys.

Another interesting idea that this paper raises is the implication of sleep on prospective memory in old people. It has been found that prospective memory is one memory that is especially impaired and gets worse with old age (they keep forgetting to get the groceries for instance). Old people also get less sleep, especially sleep of the slow wave kind. Coincidence? :)


Scullin MK, & McDaniel MA (2010). Remembering to execute a goal: sleep on it! Psychological science : a journal of the American Psychological Society / APS, 21 (7), 1028-35 PMID: 20519489

Why does Time Slow to a Crawl when we Engage in Laborous Tasks?

"Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute."

- Albert Einstein, on Relativity.


Kathleen Vohs and Brandon Schmeichel, particularly fascinated with Einstein's first observation, sought to establish whether regulating the self can elongate the 'felt' duration of time. "Because people who are self-regulating tend to monitor their behaviour, they are likely to be attuned to the passage of time," explain the authors, "these monitoring responses and resultant attention to time are not found among people who are not regulating."

In simpler terms, 'self-regulation' is likely to be linked with the attention to time. In earlier studies on duration judgment, when participants were asked after watching a TV episode to estimate the length of the episode, they gave shorter time estimates than participants who were told that they had to guess the duration of the episode prior to watching it. It appears that conscious deliberation, as opposed to the non-regulated state of automatic processing, might lead one to be more aware of time passing.

Thus, hypothesizing that deliberate, conscious and effortful self-regulation would lead one to feeling like time has passed slowly, Vohs and Schmeichel conducted four illuminating studies that lent scientific support to the claim.

In Study 1, the authors made participants watch a clip from the film Terms of Endearment, which shows a dying mother saying good-bye to her children, husband and mother. Participants were made to either naturally respond to what they saw, or suppress their emotions or exaggerate their emotions while watching the show. This manipulation had been found in earlier studies to be effective in causing participants to consciously regulate their emotions which led to diminished self-control capacity.

Participants were instructed to estimate the length of the video clip after the 11 min 23 sec clip ended.

It was found that participants who exaggerated or suppressed their emotions perceived that the film clip had lasted longer than participants who were natural during the film.





In Study 2, a similar experimental set up was used, although the film was changed from Terms of Endearment to Mondo Cane (depicting the death of wildlife). To determine that longer judgments of time were due to self-regulation specifically and not generic information processing, a new condition called 'reappraisal' was introduced. Participants in the reappraisal group were instructed to view the affectively-charged scenes in a detached manner. The authors explain: "Prior studies have shown that effects associated with emotion control (e.g. memory decrements because of emotion suppression) are absent when participants are given a reappraisal framework within which to view an emotional scene."

Participants were, again, then asked to judge how long the clip lasted.



The results support the idea that the Natural and Reappraisal conditions, which did not require self-monitoring, did not prompt the attention to time that was present in the Suppress condition.

In Study 3, participants were told to read aloud pages of text that corresponded to various types of professions. In the behavioural control group, participants were instructed to 'act out' the profession as depicted by the text, and thus they had to do their best to "act happy, smile and 'get into it'" as expected of the profession. Participants in the no condition group weren't given any such instructions.

After 4 minutes and 23 seconds had passed, participants were interrupted with a questionnaire asking them how long they thought the experiment had lasted. After that, participants were told that they could continue up to a cap of 15 minutes and stop at anytime in between.

Once again, the findings of the first two studies were replicated in the results of Study 3 as participants in the behavioural control group felt that they spent a longer time doing the task than participants in the no condition group. Continuance of the task was also affected by the manipulation, as "the longer participants believed they had been doing the read-aloud task, the shorter they continued with it after the 4:23 mark."

From this, the authors built a model that linked the experimental conditions and subsequent regulatory ability.

The results of this model were supportive of the hypothesis that time perception is a mediator. This model was further supported by a final study.


Thus, across four experiments, the authors found that people's perceptions of the duration of an activity were significantly affected by self-regulatory resource depletion. Whenever some form of cognitive regulation is involved, for instance, emotion regulation or self regulation, people can believe that the task involved lasted much longer. "A taxing self-regulatory activity is remembered as being overly long."

Where Einstein's latter observation is concerned, it might thus be likely that sitting with an attractive member of the opposite sex constitutes a very enjoyable process that requires less self regulation, which makes us less conscious of the passage of time. So, where does this place those who experience anxiety approaching attractive members of the opposite sex?


Vohs, K., & Schmeichel, B. (2003). Self-regulation and extended now: Controlling the self alters the subjective experience of time. Journal of Personality and Social Psychology, 85 (2), 217-230 DOI: 10.1037/0022-3514.85.2.217