https://www.givedirectly.org/ is the website, and the homepage answers a lot of questions.
> tracking spending habits could be construed as a condition of receiving subsequent installments and thus change the recipients' behavior into what they think GD wants them to spend it on, rather than what they'd actually want to spend it on.
I agree that https://en.wikipedia.org/wiki/Observer_effect_(physics) is probably true, but the the question is really hard to answer or put in perspective because "what I want to spend money on" changes based on lots of factors, not least of which is the amount received.
It is also likely that getting three payments changes the spending from receiving a single payment, which would be different to the spending from GD's latest program, https://www.givedirectly.org/basic-income, a test to "... scientifically test the idea of a universal basic income by providing regular cash payments to thousands of extremely poor households in East Africa for more than ten years."
There are sooooooo many questions about cash transfers, and given the almost complete lack of administrative costs - $0.91 in every dollar ending up in a poor person's hand is insane - they are all worth investigating. Your question is likely item 9,999 on that list :)
As an example of the questions that need an answer, one I found interesting was this: https://www.givedirectly.org/blog-post?id=334321986851653361...
> In Uganda and Rwanda more than 96% of eligible recipients have opted in, respectively. > ... In July 2015 we entered Homa Bay, a new county and our first venture outside of Siaya. In Homa Bay and the neighboring areas, roughly 45% of the households we speak with decline to be enrolled into the program.
It is amazing that people will give up free money, and shows the lengths GD goes to investigate the problems surrounding cash transfers.