I have read that you should begin showing your baby “cause and effect” at around 7 months. On the contrary! It is never too early to begin and I have the video to prove it! But do you really have to take my word (or video) as proof? One of the first consequences a baby learns is that when she cries then someone will come. If she is hungry then someone feeds her. When she puts her fist in her mouth and sucks, it soothes her. Your baby realizes that she can make things happen.
And by the way, continue doing all the things that make your baby feel good and secure and comfortable and loved. You will not spoil a baby by comforting her (i.e. picking her up) when she cries and needs to be soothed. Babies need comfort and love and the feeling of security.
So given that we know your baby causes a reaction from you, how about a fun way to cause a reaction from her?!
In this video you will see me “creep” my hands up my sons legs then tickle him under the chin. By the third time watch how he begins to laugh before I barely begin to move my hands! THAT is infant stimulation. THAT is learning. THAT is brain development. And he is not 7 months old; he is 4 months!