Curt Adams writes:
>>They are trying to use the timing of variables to infer causality;
>>things that are measured earlier likely cause, and are not caused by,
>>things that are measured later. So to disambiguate cause, they measure
>>soc/psych both before and after internet use. Of course there's always
>>the possiblity of unmeasured variables causing everything, such as
>>unmeasured "during" soc/psych. But it seems to me they have done the
>>reasonable thing with the data the have.
>
>Even by that standard, then, they've overreached in deducing causation.
>Neither the family communication-usage nor depression-usage correlations
>changed significantly from pre to post, although loneliness probably
>did.
>Also, the *change* in psychological state is contemporaneous with
>internet use, and so with respect to that as a causative factor, they
>don't have temporal control. If *losing* friends makes people turn
>to the internet (as opposed to not having them in the first place)
>then you get the reported results, even with the reverse of the inferred
>causation.
Robin Hanson
hanson@econ.berkeley.edu http://hanson.berkeley.edu/
RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884
140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-8614