How Effective were Spears Against Cavalry?

[Macedon]

We do have descriptions of cavalry charging towards infantry, but towards and into are two different things. In another thread about the same issue I had suggested that in my opinion, medieval infantry was inferior in many aspects to ancient infantry, especially regarding discipline, professionalism and quality of leadership (particularly lower rank officers). This made the chances of an infantry line withstanding the psychological impact of an impressive cavalry charge even more difficult than it was before. It was also much harder to muster large numbers of men (let alone men trained in warfare) and as such, battles tended to be less tactical and more skirmishing/irregular, a must for cavalry bodies to be able to excel. Yet, even in those years, we see that cavalry again did not often (that is as a regular tactical choice instead of getting the command as a result of their commanding officer wishing to exploit some weakness he thought he saw in the enemy force) resort to such cavalry charges. For example, look at how many charges the Normans did at Hastings or in many other battles, often given in number of two digits. And also look at the results... The former shows that these charges were not as suicidal as they would be if they resembled to what we are discussing here (my opinion being that they were taunting their target, stopping and retreating, riding by or maybe some individual knights charging or pushing into the line) and the latter that infantry did hold its place, even though its armament and discipline could not really compare to this of the ancients, besting even the most renowned cavalry of the time. In the end, it took the Saxons voluntarily breaking their lines, running down the hill in an imaginary pursuit of their enemy to allow William's knights to run them down. As for the Scottish shiltrons, they resembled the Seleucid pike squares (although a shiltron was not only rectangular in shape) we read of at Magnesia and their density made them a formidable opponent on the British battlegrounds of the era.