Dom Joly: What has four legs and the IQ of a guppy? My dog

What do you do when you realise that your dog is a moron? Don't get me wrong, I love both my dogs, it's just that Oscar, the younger of the two, is monumentally stupid.

He's a flat-coat retriever and now, every time I grumble about him, everybody says, "Oh yes, they're renowned for being really dumb." Strangely, nobody chose to mention this when I bought him. I didn't turn up at the seller's for him to say "Yes, he's a handsome hound – unfortunately, he has the IQ of a guppy fish and a memory of about seven seconds." Of course, he didn't – he was selling him to me.

It doesn't help that my other dog, Huxley, is a supremely gifted black labrador who, I'm convinced, regularly communicates with me. There is so much wisdom in his coal-black eyes that I feel he is something akin to a dog genius. Oscar regularly communicates with the food recycling bin and spreads the rotting stuff all over our house every morning. Possibly he is trying to communicate by spelling out letters in old bananas and chicken bones, but, if he is, I have so far been unable to crack his code.

Sometimes I'll be upstairs, looking out of the window, when I spot Oscar in the garden. He wanders out then suddenly gets very panicky as his seven-second memory is wiped clean. "What am I doing here? Where am I? What is all this green stuff?" I can see him struggling with his very existence as he bolts back inside where he immediately panics again, "What is this place? Look, two-legged beings... very, very frightening...."

He is a very sweet dog and loves nothing more than attention, but he is difficult to love. I'm curious as to what flat-coat retrievers were bred for, originally. I'm presuming that the word "retriever" is a clue. But what does he retrieve? If I throw a tennis ball for Huxley, he will swim across rivers, climb trees and use a complicated grid-search system to scan an area if the ball becomes hidden. He has never lost a ball in his nine years of existence.

If you throw a ball for Oscar, it's 50-50 whether he'll even set off in the right direction. If he does manage this minor miracle then he'll lollop off, but inevitably come to a halt after about six seconds and stare vacantly around. You can see him wondering what on earth he is doing. You might mistake this for him pondering on the meaning of life. Maybe he is struggling with a tricky mathematical conundrum? You might think that, but you would be wrong. He looks back at me for a second and then rolls around in the grass hoping that this is what I'm wanting from him. It's a desperate sight.

The idea that Oscar could be on a shoot and would rush from my gun to retrieve a dead bird and bring it back is laughable. The only thing I could imagine him retrieving is a pheasant, the dumbest of all God's creatures. My drive home from London is a veritable killing zone as pheasant after pheasant hurls itself at my car. If I try to swerve right, the pheasant will follow me. They are either unbelievably thick or someone down here is breeding kamikaze versions of the bird. Even Oscar would have no trouble catching one as he could just sit in one of his usual, confused states and the pheasant would launch itself into his grateful jaws.

As I sit here writing this, Oscar has spotted himself in the mirror; his hackles have risen and he is on full alert at this intruder. When the time comes for us to get our next dog, I am going to insist that he takes an IQ test before being allowed into our home. Harsh, but true.