WBB: the article seems to be a riff on attachment theory, which is about how a child's relationship with its primary caregiver affects its social development. Maybe you would be interested in reading up on that?
Here is an amateur synopsis:
The basic idea is that there is an attachment period--starting usually at around 6 months old--when a baby needs to create a bond with one special person so that it knows it is safe and protected and seen. Failure in attachment impacts the child's later ability to regulate emotions. The bulk of the formation of that bond supposedly happens the first year, though attachment behavior goes on up until around three.
The quality of that attachment varies a lot. For instance, if a caregiver who depressed during the attachment period, or ill, or is for any other reason distracted from the baby, or obviously if the baby is abused by the primary caregiver, the attachment suffers. Also, prolonged periods of separation and a lot of moving around are not good for attachment. In general, the idea is to create a stable, predictable one on one relationship that becomes a platform from which to explore the world.
(Incidentally, I recently learned that I was left with a babysitter for a month when I was 10-11 months old--a big no-no! Also, my mother suffered from depression, and I moved 10 times over three states by the time I was three. OOPS!)
Anyhow... .
Attachment theory makes reference to four behavior patterns that correspond to different attachment styles. They came out of an experiment in which babies were observed responding to situations in which they are separated from caregivers and introduced to strangers. (It's more in-depth than that, but this is the basic idea, I think.) Behavior generally fell into four categories. I will cut and paste. The first three patterns more or less correspond to the styles in the article
Secure Attachment: A child who is securely attached to its caregiver will explore freely while the caregiver is present, will engage with strangers, will be visibly upset when the caregiver departs, and happy to see the caregiver return.
The child will not engage with the stranger if the caregiver is not in the room.
Anxious-Ambivalent Insecure Attachment: A child with an anxious-resistant attachment style is anxious of exploration and of strangers, even when the caregiver is present. When the caregiver departs, the child is extremely distressed. The child will be ambivalent when she returns and will seek to remain close to the caregiver, but will be resentful, and also resistant when the caregiver initiates attention.
Anxious-Avoidant Insecure Attachment: A child with an anxious-avoidant attachment style will avoid or ignore the caregiver and show little emotion when the caregiver departs or returns. The child will not explore very much, regardless of who is there. Strangers will not be treated very differently from the caregiver. There is not much emotional range displayed regardless of who is in the room or if it is empty.
A fourth patterns was identified later, which does not seem to have an analog in that article:
Disorganized Attachment: the child expresses odd or ambivalent behavior toward the parent, (i.e. first running up to them, then immediately pulling away, perhaps even running away from the parent, curling up in a ball or hitting the parent.) The child’s first impulse may be to seek comfort from the parent, but as they get near the parent, they feel fear to be in their proximity, demonstrating their disorganized adaption.
Each of those behavior patterns are predictive of later behavior in relationships, which is where that article comes in.
EDIT: there's a wikipedia entry for Mary Ainsworth's experiment, which is called the Strange Situaion test.
https://en.wikipedia.org/wiki/Strange_situation
